Programs & Examples On #Javascript

JavaScript (not to be confused with Java) is a high-level, dynamic, multi-paradigm, weakly-typed language used for both client-side and server-side scripting. Its primary use is in rendering and allowing manipulation of web pages. Use this tag for questions regarding ECMAScript and its various dialects/implementations (excluding ActionScript and Google-Apps-Script).

How to convert a plain object into an ES6 Map?


convert object to map:

const objToMap = (o) => new Map(Object.entries(o));

convert map to object:

const mapToObj = (m) => [...m].reduce( (o,v)=>{ o[v[0]] = v[1]; return o; },{} )

Note: the mapToObj function assumes map keys are strings (will fail otherwise)

How to check whether a Storage item is set?

if(!localStorage.hash) localStorage.hash = "thinkdj";


var secret =  localStorage.hash || 42;

JavaScript Loading Screen while page loads

This method uses the WindowOrWorkerGlobalScope.setInterval( method to track the ready states of the document & see if the <body> element exists.

// Function > Loader Screen Script
(function LoaderScreenScript(window = window, document = window.document, undefined = window.undefined || void 0) {
    // Initialization > (Processing Time, Condition, Timeout, Loader (...))
    let processingTime = 0,
        condition = function() {
            // Return
            return document.body
        timeout = function() {
            // Return
            return (processingTime * 1e3) / 2
        loaderScreenFontSize = typeof window.loaderScreenFontSize != 'undefined' ? window.loaderScreenFontSize : 14,
        loaderScreenMargin = typeof window.loaderScreenMargin != 'undefined' ? window.loaderScreenMargin : 10,
        loaderScreenMessage = typeof window.loaderScreenMessage != 'undefined' ? window.loaderScreenMessage : 'Loading, please wait&hellip;',
        loaderScreenOpacity = typeof window.loaderScreenOpacity != 'undefined' ? window.loaderScreenOpacity : .75,
        loaderScreenTransition = typeof window.loaderScreenTransition != 'undefined' ? window.loaderScreenTransition : .675,
        loaderScreenWidth = typeof window.loaderScreenWidth != 'undefined' ? window.loaderScreenWidth : 7.5;

    // Function > Update
    function update() {
        // Set Timeout
        setTimeout(function() {
            // Initialization > (Data, Metadata)
            var data = document.createElement('loader-screen-element'),
                metadata = setInterval(function() {
                    /* Logic
                            [if:else if:else statement]
                    if (document.readyState == 'complete') {
                        // Alpha

                        // Test

            // Insertion

            // Style > <body> > Overflow
   = ('overflow: hidden !important; pointer-events: none !important; user-drag: none !important; user-select: none !important;' + (document.body.getAttribute('style') || ' ')).trim();

            // Modification > Data
                // Inner HTML
                data.innerHTML =
                    '<style media=all type=text/css>' +
                        'body::selection {' +
                            'background-color: transparent !important;' +
                            'text-shadow: none !important' +
                        '} ' +
                        '@keyframes rotate {' +
                            '0% { transform: rotate(0) }' +
                            'to { transform: rotate(360deg) }' +
                        '}' +
                    '</style>' +
                    "<div style='animation: rotate 1s ease-in-out 0s infinite backwards; border: " + loaderScreenWidth + "px solid rgba(0, 0, 0, " + loaderScreenOpacity + "); border-top-color: rgba(0, 51, 255, " + loaderScreenOpacity + "); border-radius: 50%; height: 75px; margin: 0 auto; margin-bottom: " + loaderScreenMargin + "px; width: 75px'> </div>" +
                    "<small style='color: rgba(127, 127, 127, .675); font-family: \"Open Sans\", \"Calibri Light\", Calibri, sans-serif; font-size: " + loaderScreenFontSize + "px !important; margin: 0 auto; margin-top: " + loaderScreenMargin + "px; text-align: center'> " + loaderScreenMessage + " </small>";

                // Style
       = 'align-items: center; background-color: rgba(255, 255, 255, .98); display: flex; flex-direction: column; height: ' + innerHeight + 'px; justify-content: center; left: 0; margin: auto; max-height: 100% !important; max-width: 100% !important; min-height: 100vh; min-width: 100vh; position: fixed; top: 0; transition: ' + loaderScreenTransition + 's ease-in-out; width: ' + innerWidth + 'px; z-index: 2147483647';

            // Function
                // Alpha
                function alpha() {
                    // Clear Interval

                // Test
                function test() {
                    // Style > Data
                        // Background Color
               = 'transparent';

                        // Opacity
               = 0;

                    // Set Timeout
                    setTimeout(function() {
                        // Deletion

                        // Modification > <body> > Style
               = document.body.getAttribute('style').replace('overflow: hidden !important;', '').replace('pointer-events: none !important;', '').replace('user-drag: none !important;', '').replace('user-select: none !important;', '');
                        (document.body.getAttribute('style') || '').trim() || document.body.removeAttribute('style')
                    }, ((+getComputedStyle(data).getPropertyValue('animation-delay').replace(/[a-zA-Z]/g, '').trim() + +getComputedStyle(data).getPropertyValue('animation-duration').replace(/[a-zA-Z]/g, '').trim() + +getComputedStyle(data).getPropertyValue('transition-delay').replace(/[a-zA-Z]/g, '').trim() + +getComputedStyle(data).getPropertyValue('transition-duration').replace(/[a-zA-Z]/g, '').trim()) * 1e3) + 100);
        }, timeout())

    /* Logic
            [if:else if:else statement]
    if (condition())
        // Update

    else {
        // Initialization > Data
        var data = setInterval(function() {
            /* Logic
                    [if:else if:else statement]
            if (condition()) {
                // Update > Processing Time
                processingTime += 1;

                // Update

                // Metadata

        // Function > Metadata
        function metadata() {
            // Clear Interval

            /* Logic
                    [if:else if:else statement]

                > Deletion
            if ('data' in window && typeof data == 'undefined')
})(window, window.document, window.undefined || void 0)

This pre-loading screen was made by Lapys @

How to stop event bubbling on checkbox click

Don't forget IE:

if (event.stopPropagation) {    // standard
    } else {    // IE6-8
        event.cancelBubble = true;

Moment.js - how do I get the number of years since a date, not rounded up?

Using moment.js is as easy as:

var years = moment().diff('1981-01-01', 'years');
var days = moment().diff('1981-01-01', 'days');

For additional reference, you can read moment.js official documentation.

Call external javascript functions from java code

try {
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("JavaScript");
        FileInputStream fileInputStream = new FileInputStream("C:/Users/Kushan/eclipse-workspace/");
        if (fileInputStream != null){
         BufferedReader reader = new BufferedReader(new InputStreamReader(fileInputStream));
        // Invocable javascriptEngine = null;
        Invocable invocableEngine = (Invocable)engine;
         int x=0;
         System.out.println("invocableEngine is : "+invocableEngine);
         Object object = invocableEngine.invokeFunction("backend_message",x);

        }catch(Exception e) {
            System.out.println("erroe when calling js function"+ e);

How do I check if an object has a key in JavaScript?

Try the JavaScript in operator.

if ('key' in myObj)

And the inverse.

if (!('key' in myObj))

Be careful! The in operator matches all object keys, including those in the object's prototype chain.

Use myObj.hasOwnProperty('key') to check an object's own keys and will only return true if key is available on myObj directly:


Unless you have a specific reason to use the in operator, using myObj.hasOwnProperty('key') produces the result most code is looking for.

Embedding VLC plugin on HTML page

test.html is will be helpful for how to use VLC WebAPI.

test.html is located in the directory where VLC was installed.

e.g. C:\Program Files (x86)\VideoLAN\VLC\sdk\activex\test.html

The following code is a quote from the test.html.


<object classid="clsid:9BE31822-FDAD-461B-AD51-BE1D1C159921" width="640" height="360" id="vlc" events="True">
  <param name="MRL" value="" />
  <param name="ShowDisplay" value="True" />
  <param name="AutoLoop" value="False" />
  <param name="AutoPlay" value="False" />
  <param name="Volume" value="50" />
  <param name="toolbar" value="true" />
  <param name="StartTime" value="0" />
  <EMBED pluginspage=""
    text="Waiting for video"


You can get vlc object from getVLC().
It works on IE 10 and Chrome.

function getVLC(name)
    if (window.document[name])
        return window.document[name];
    if (navigator.appName.indexOf("Microsoft Internet")==-1)
        if (document.embeds && document.embeds[name])
            return document.embeds[name];
    else // if (navigator.appName.indexOf("Microsoft Internet")!=-1)
        return document.getElementById(name);

var vlc = getVLC("vlc");

// do something.
// e.g.;

What is the meaning of polyfills in HTML5?

First off let's clarify what a polyfil is not: A polyfill is not part of the HTML5 Standard. Nor is a polyfill limited to Javascript, even though you often see polyfills being referred to in those contexts.

The term polyfill itself refers to some code that "allows you to have some specific functionality that you expect in current or “modern” browsers to also work in other browsers that do not have the support for that functionality built in. "

Source and example of polyfill here:

Replacing &nbsp; from javascript dom text node

for me replace doesn't work... try this code:

str = str.split("&quot;").join('"');

ES6 exporting/importing in index file

Nav.js comp inside components folder

export {Nav}

index.js in component folder

export {Nav} from './Nav';
export {Another} from './Another';

import anywhere

import {Nav, Another} from './components'

force browsers to get latest js and css files in application

In ASP.NET Core (MVC 6) this works out of the box via the asp-append-version tag helper:

<script src="scripts/myjavascript.js" asp-append-version="true"></script>
<link href="styles/mystyle.css rel="stylesheet" asp-append-version="true" />

endsWith in JavaScript

This is the implementation of endsWith:

String.prototype.endsWith = function (str) {
  return (this.length >= str.length) && (this.substr(this.length - str.length) === str);

Get the size of the screen, current web page and browser window

Sometimes you need to see the width/height changes while resizing the window and inner content.

For that I've written a little script that adds a log box that dynamicly monitors all the resizing and almost immediatly updates.

It adds a valid HTML with fixed position and high z-index, but is small enough, so you can:

  • use it on an actual site
  • use it for testing mobile/responsive views

Tested on: Chrome 40, IE11, but it is highly possible to work on other/older browsers too ... :)

  function gebID(id){ return document.getElementById(id); }
  function gebTN(tagName, parentEl){ 
     if( typeof parentEl == "undefined" ) var parentEl = document;
     return parentEl.getElementsByTagName(tagName);
  function setStyleToTags(parentEl, tagName, styleString){
    var tags = gebTN(tagName, parentEl);
    for( var i = 0; i<tags.length; i++ ) tags[i].setAttribute('style', styleString);
  function testSizes(){
    gebID( 'screen.Width' ).innerHTML = screen.width;
    gebID( 'screen.Height' ).innerHTML = screen.height;

    gebID( 'window.Width' ).innerHTML = window.innerWidth;
    gebID( 'window.Height' ).innerHTML = window.innerHeight;

    gebID( 'documentElement.Width' ).innerHTML = document.documentElement.clientWidth;
    gebID( 'documentElement.Height' ).innerHTML = document.documentElement.clientHeight;

    gebID( 'body.Width' ).innerHTML = gebTN("body")[0].clientWidth;
    gebID( 'body.Height' ).innerHTML = gebTN("body")[0].clientHeight;  

  var table = document.createElement('table');
  table.innerHTML = 
      +"<tr><td>screen</td><td id='screen.Width' /><td>x</td><td id='screen.Height' /></tr>"
      +"<tr><td>window</td><td id='window.Width' /><td>x</td><td id='window.Height' /></tr>"
      +"<tr><td>document<br>.documentElement</td><td id='documentElement.Width' /><td>x</td><td id='documentElement.Height' /></tr>"
      +"<tr><td>document.body</td><td id='body.Width' /><td>x</td><td id='body.Height' /></tr>"

  gebTN("body")[0].appendChild( table );

     "border: 2px solid black !important; position: fixed !important;"
     +"left: 50% !important; top: 0px !important; padding:10px !important;"
     +"width: 150px !important; font-size:18px; !important"
     +"white-space: pre !important; font-family: monospace !important;"
     +"z-index: 9999 !important;background: white !important;"
  setStyleToTags(table, "td", "color: black !important; border: none !important; padding: 5px !important; text-align:center !important;");
  setStyleToTags(table, "th", "color: black !important; border: none !important; padding: 5px !important; text-align:center !important;"); 'margin-left', '-'+( table.clientWidth / 2 )+'px' );

  setInterval( testSizes, 200 );

EDIT: Now styles are applied only to logger table element - not to all tables - also this is a jQuery-free solution :)

React-Router External link

I don't think React-Router provides this support. The documentation mentions

A < Redirect > sets up a redirect to another route in your application to maintain old URLs.

You could try using something like React-Redirect instead

How to convert unix timestamp to calendar date moment.js

moment(timestamp).format('''any format''')

react-router go back a page how do you configure history?

  1. import withRouter

    import { withRouter } from 'react-router-dom';
  2. Export your component as:

    export withRouter(nameofcomponent) 
  3. Example, on button click, call goBack:

    <button onClick={this.props.history.goBack}>Back</button>

Tested on react-router-dom v4.3

jQuery remove options from select

Iterating a list and removing multiple items using a find. Response contains an array of integers. $('#OneSelectList') is a select list.

    url: "Controller/Action",
    type: "GET",
    success: function (response) {
        // Take out excluded years.
        $.each(response, function (j, responseYear) {
            $('#OneSelectList').find('[value="' + responseYear + '"]').remove();
    error: function (response) {

node.js shell command execution

Simplest way is to just use the ShellJS lib ...

$ npm install [-g] shelljs

EXEC Example:


// Sync call to exec()
var version = exec('node --version', {silent:true}).output;

// Async call to exec()
exec('netstat.exe -an', function(status, output) {
  console.log('Exit status:', status);
  console.log('Program output:', output);
}); supports many common shell commands mapped as NodeJS functions including:

  • cat
  • cd
  • chmod
  • cp
  • dirs
  • echo
  • exec
  • exit
  • find
  • grep
  • ln
  • ls
  • mkdir
  • mv
  • popd
  • pushd
  • pwd
  • rm
  • sed
  • test
  • which

Iterating over every property of an object in javascript using Prototype?

You should iterate over the keys and get the values using square brackets.

See: How do I enumerate the properties of a javascript object?

EDIT: Obviously, this makes the question a duplicate.

Why Is `Export Default Const` invalid?

const is like let, it is a LexicalDeclaration (VariableStatement, Declaration) used to define an identifier in your block.

You are trying to mix this with the default keyword, which expects a HoistableDeclaration, ClassDeclaration or AssignmentExpression to follow it.

Therefore it is a SyntaxError.

If you want to const something you need to provide the identifier and not use default.

export by itself accepts a VariableStatement or Declaration to its right.

AFAIK the export in itself should not add anything to your current scope.

The following is fineexport default Tab;

Tab becomes an AssignmentExpression as it's given the name default ?

export default Tab = connect( mapState, mapDispatch )( Tabs ); is fine

Here Tab = connect( mapState, mapDispatch )( Tabs ); is an AssignmentExpression.

Getting binary (base64) data from HTML5 Canvas (readAsBinaryString)

Seeing how you draw your canvas with


it seems that you use jQuery Canvas (jCanvas) by Caleb Evans. I actually use that plugin and it has a simple way to retrieve canvas base64 image string with $('canvas').getCanvasImage();

Here's a working Fiddle for you:

how to compare two elements in jquery

You could compare DOM elements. Remember that jQuery selectors return arrays which will never be equal in the sense of reference equality.


<div id="a" class="a"></div>


$('div.a')[0] == $('div#a')[0]

returns true.

Go Back to Previous Page

You specifically asked for JS solutions, but in the event that someone visits your form with JS disabled a PHP backup is always nice:

when the form loads grab the previous page address via something like $previous = $_SERVER['HTTP_REFERER']; and then set that as a <input type="hidden" value="$previous" /> in your form. When you process your form with the script you can grab that value and stick it in the header("Location:___") or stick the address directly into a link to send them back where they came from

No JS, pretty simple, and you can structure it so that it's only handled if the client doesn't have JS enabled.

How to check if type is Boolean

I would go with Lodash: isBoolean checks whether the passed-in variable is either primitive boolean or Boolean wrapper object and so accounts for all cases.

Javascript reduce() on Object

Try this one. It will sort numbers from other variables.

const obj = {
   a: 1,
   b: 2,
   c: 3
const result = Object.keys(obj)
.reduce((acc, rec) => typeof obj[rec] === "number" ? acc.concat([obj[rec]]) : acc, [])
.reduce((acc, rec) => acc + rec)

How to prevent user from typing in text field without disabling the field?

A non-Javascript alternative that can be easily overlooked: can you use the readonly attribute instead of the disabled attribute? It prevents editing the text in the input, but browsers style the input differently (less likely to "grey it out") e.g. <input readonly type="text" ...>

Truncate/round whole number in JavaScript?

Math.trunc() function removes all the fractional digits.

For positive number it behaves exactly the same as Math.floor():

console.log(Math.trunc(89.13349)); // output is 89

For negative numbers it behaves same as Math.ceil():

console.log(Math.trunc(-89.13349)); //output is -89

How do I create a custom Error in JavaScript?

All of the above answers are terrible awful - really. Even the one with 107 ups! The real answer is here guys:

Inheriting from the Error object - where is the message property?


A. The reason message isn't being set is that Error is a function that returns a new Error object and does not manipulate this in any way.

B. The way to do this right is to return the result of the apply from the constructor, as well as setting the prototype in the usual complicated javascripty way:

function MyError() {_x000D_
    var temp = Error.apply(this, arguments);_x000D_ = = 'MyError';_x000D_
    this.message = temp.message;_x000D_
    if(Object.defineProperty) {_x000D_
        // getter for more optimizy goodness_x000D_
        /*this.stack = */Object.defineProperty(this, 'stack', { _x000D_
            get: function() {_x000D_
                return temp.stack_x000D_
            configurable: true // so you can change it if you want_x000D_
    } else {_x000D_
        this.stack = temp.stack_x000D_
//inherit prototype using ECMAScript 5 (IE 9+)_x000D_
MyError.prototype = Object.create(Error.prototype, {_x000D_
    constructor: {_x000D_
        value: MyError,_x000D_
        writable: true,_x000D_
        configurable: true_x000D_
var myError = new MyError("message");_x000D_
console.log("The message is: '" + myError.message + "'"); // The message is: 'message'_x000D_
console.log(myError instanceof Error); // true_x000D_
console.log(myError instanceof MyError); // true_x000D_
console.log(myError.toString()); // MyError: message_x000D_
console.log(myError.stack); // MyError: message \n _x000D_
// <stack trace ...>_x000D_
//for EMCAScript 4 or ealier (IE 8 or ealier), inherit prototype this way instead of above code:_x000D_
var IntermediateInheritor = function() {};_x000D_
IntermediateInheritor.prototype = Error.prototype;_x000D_
MyError.prototype = new IntermediateInheritor();_x000D_

You could probably do some trickery to enumerate through all the non-enumerable properties of the tmp Error to set them rather than explicitly setting only stack and message, but the trickery isn't supported in ie<9

How to correctly iterate through getElementsByClassName

You could always use array methods:

var slides = getElementsByClassName("slide");, function(slide, index) {

jquery validate check at least one checkbox

 if ($('input:checkbox').filter(':checked').length < 1){
        alert("Check at least one!");
 return false;

Javascript Append Child AFTER Element

You can use:

if (parentGuest.nextSibling) {
  parentGuest.parentNode.insertBefore(childGuest, parentGuest.nextSibling);
else {

But as Pavel pointed out, the referenceElement can be null/undefined, and if so, insertBefore behaves just like appendChild. So the following is equivalent to the above:

parentGuest.parentNode.insertBefore(childGuest, parentGuest.nextSibling);

How do I use the includes method in lodash to check if an object is in the collection?

You could use find to solve your problem

const data = [{"a": 1}, {"b": 2}]
const item = {"b": 2}

find(data, item)
// > true

chart.js load totally new data

If anyone is looking for how to do this in React. For a linechart, assuming you have a wrapper component around the chart:

(This assumes you are using v2. You do not need to use react-chartjs. This is using the normal chart.js package from npm.)

propTypes: {
  data: React.PropTypes.shape({
    datasets: React.PropTypes.arrayOf(

    labels: React.PropTypes.array.isRequired
componentDidMount () {
  let chartCanvas = this.refs.chart;

  let myChart = new Chart(chartCanvas, {
    type: 'line',
    options: {

  this.setState({chart: myChart});
componentDidUpdate () {
    let chart = this.state.chart;
    let data =;

    data.datasets.forEach((dataset, i) =>[i].data =; = data.labels;
render () {
  return (
    <canvas ref={'chart'} height={'400'} width={'600'}></canvas>

The componentDidUpdate functionality allows you to update, add, or remove any data from the

Using Razor within JavaScript

That will work fine, as long as it's in a CSHTML page and not an external JavaScript file.

The Razor template engine doesn't care what it's outputting and does not differentiate between <script> or other tags.

However, you need to encode your strings to prevent XSS attacks.

What is the javascript filename naming convention?

One possible naming convention is to use something similar to the naming scheme jQuery uses. It's not universally adopted but it is pretty common.


where the product-name + plugin pair can also represent a namespace and a module. The version and filetype are usually optional.

filetype can be something relative to how the content of the file is. Often seen are:

  • min for minified files
  • custom for custom built or modified files


  • jquery-1.4.2.min.js
  • jquery.plugin-0.1.js
  • myapp.invoice.js

javascript toISOString() ignores timezone offset

moment.js is great but sometimes you don't want to pull a large number of dependencies for simple things.

The following works as well:

var tzoffset = (new Date()).getTimezoneOffset() * 60000; //offset in milliseconds
var localISOTime = (new Date( - tzoffset)).toISOString().slice(0, -1);
// => '2015-01-26T06:40:36.181'

The slice(0, -1) gets rid of the trailing Z which represents Zulu timezone and can be replaced by your own.

Function to calculate distance between two coordinates

Adding this for Node.JS users. You can use the haversine-distance module to do this so you won't need to handle the calculations on your own. See the npm page for more information.

To install:

npm install --save haversine-distance

You can use the module as follows:

var haversine = require("haversine-distance");

//First point in your haversine calculation
var point1 = { lat: 6.1754, lng: 106.8272 }

//Second point in your haversine calculation
var point2 = { lat: 6.1352, lng: 106.8133 }

var haversine_m = haversine(point1, point2); //Results in meters (default)
var haversine_km = haversine_m /1000; //Results in kilometers

console.log("distance (in meters): " + haversine_m + "m");
console.log("distance (in kilometers): " + haversine_km + "km");

Pure JavaScript: a function like jQuery's isNumeric()

var str = 'test343',
    isNumeric = /^[-+]?(\d+|\d+\.\d*|\d*\.\d+)$/;


Trim string in JavaScript?

Flagrant Badassery has 11 different trims with benchmark information:

Non-surprisingly regexp-based are slower than traditional loop.

Here is my personal one. This code is old! I wrote it for JavaScript1.1 and Netscape 3 and it has been only slightly updated since. (Original used String.charAt)

 *  Trim string. Actually trims all control characters.
 *  Ignores fancy Unicode spaces. Forces to string.
function trim(str) {
    str = str.toString();
    var begin = 0;
    var end = str.length - 1;
    while (begin <= end && str.charCodeAt(begin) < 33) { ++begin; }
    while (end > begin && str.charCodeAt(end) < 33) { --end; }
    return str.substr(begin, end - begin + 1);

Console.log(); How to & Debugging javascript

Essentially console.log() allows you to output variables in your javascript debugger of choice instead of flashing an alert() every time you want to inspect something... additionally, for more complex objects it will give you a tree view to inspect the object further instead of having to convert elements to strings like an alert().

jQuery get an element by its data-id

You can always use an attribute selector. The selector itself would look something like:


javascript: optional first argument in function

I've created a simple library for handling optional arguments with JavaScript functions, see The library is developed with Node.js in mind but should be easily ported to work with e.g. browsers.


var argShim = require('argShim');
var defaultOptions = {
  myOption: 123

var my_function = argShim([
  ], function(content, options) {
    console.log("content:", content, "options:", options);

my_function('str', {myOption:42});


content: undefined options: { myOption: 123 }
content: str options: { myOption: 123 }
content: undefined options: { myOption: 42 }
content: str options: { myOption: 42 }

The main target for the library are module interfaces where you need to be able to handle different invocations of exported module functions.

How to apply !important using .css()?

You can achieve this in two ways:

$("#elem").prop("style", "width: 100px !important"); // this is not supported in chrome
$("#elem").attr("style", "width: 100px !important");

How to add an object to an array

Put anything into an array using Array.push().

var a=[], b={};
// a[0] === b;

Extra information on Arrays

Add more than one item at a time

var x = ['a'];
x.push('b', 'c');
// x = ['a', 'b', 'c']

Add items to the beginning of an array

var x = ['c', 'd'];
x.unshift('a', 'b');
// x = ['a', 'b', 'c', 'd']

Add the contents of one array to another

var x = ['a', 'b', 'c'];
var y = ['d', 'e', 'f'];
x.push.apply(x, y);
// x = ['a', 'b', 'c', 'd', 'e', 'f']
// y = ['d', 'e', 'f']  (remains unchanged)

Create a new array from the contents of two arrays

var x = ['a', 'b', 'c'];
var y = ['d', 'e', 'f'];
var z = x.concat(y);
// x = ['a', 'b', 'c']  (remains unchanged)
// y = ['d', 'e', 'f']  (remains unchanged)
// z = ['a', 'b', 'c', 'd', 'e', 'f']

getElementById returns null?

There could be many reason why document.getElementById doesn't work

  • You have an invalid ID

    ID and NAME tokens must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens ("-"), underscores ("_"), colons (":"), and periods ("."). (resource: What are valid values for the id attribute in HTML?)

  • you used some id that you already used as <meta> name in your header (e.g. copyright, author... ) it looks weird but happened to me: if your 're using IE take a look at (resource:

  • you're targeting an element inside a frame or iframe. In this case if the iframe loads a page within the same domain of the parent you should target the contentdocument before looking for the element (resource: Calling a specific id inside a frame)

  • you're simply looking to an element when the node is not effectively loaded in the DOM, or maybe it's a simple misspelling

I doubt you used same ID twice or more: in that case document.getElementById should return at least the first element

Regular expression to get a string between two strings in Javascript

I was able to get what I needed using Martinho Fernandes' solution below. The code is:

var test = "My cow always gives milk";

var testRE = test.match("cow(.*)milk");

You'll notice that I am alerting the testRE variable as an array. This is because testRE is returning as an array, for some reason. The output from:

My cow always gives milk

Changes into:

always gives

How can I stop Chrome from going into debug mode?

I have made it working...

Please follow the highlighted mark in the attached image.

Enter image description here

How can I clear an HTML file input with JavaScript?

the input.value = null is a working method, however it will only trigger input's change event if called from an onclick event.

Solution to that would be calling that onchange handler manually whenever you need to reset the input.

function reset_input(input) {
    $(input)[0].value = null;
function input_change_handler() {
    // this happens when there's been a change in file selection

    if ($(input)[0].files.length) {
        // file(s) selected
    } else {
        // nothing is selected
$(input).on('change', input_change_handler);

Barcode scanner for mobile phone for Website in form

Scandit is a startup whose goal is to replace bulky, expensive laser barcode scanners with cheap mobile phones.

There are SDKs for Android, iOS, Windows, C API/Linux, React Native, Cordova/PhoneGap, Xamarin.

There is also Scandit Barcode Scanner SDK for the Web which the WebAssembly version of the SDK. It runs in modern browsers, also on phones.

There's a client library that also provides a barcode picker component. It can be used like this:

<div id="barcode-picker" style="max-width: 1280px; max-height: 80%;"></div>

<script src=""></script>
    ScanditSDK.configure("xxx", {
engineLocation: ""
    }).then(() => {
      ScanditSDK.BarcodePicker.create(document.getElementById('barcode-picker'), {
        playSoundOnScan: true,
        vibrateOnScan: true
      }).then(function(barcodePicker) {
        barcodePicker.applyScanSettings(new ScanditSDK.ScanSettings({
          enabledSymbologies: ["ean8", "ean13", "upca", "upce", "code128", "code39", "code93", "itf", "qr"],
          codeDuplicateFilter: 1000
        barcodePicker.onScan(function(barcodes) {

Disclaimer: I work for Scandit

Avoid dropdown menu close on click inside


  $(document).on('', '.dropdown.keep-inside-clicks-open', function (e) {


<div class="dropdown keep-inside-clicks-open">
  <button class="btn btn-primary dropdown-toggle" type="button" data-toggle="dropdown">
     Dropdown Example
    <span class="caret"></span>
  <ul class="dropdown-menu">
    <li><a href="#">HTML</a></li>
    <li><a href="#">CSS</a></li>
    <li><a href="#">JavaScript</a></li>



Your demo with this solution:

Pure JavaScript equivalent of jQuery's $.ready() - how to call a function when the page/DOM is ready for it

The good folks at HubSpot have a resource where you can find pure Javascript methodologies for achieving a lot of jQuery goodness - including ready

function ready(fn) {
  if (document.readyState != 'loading'){
  } else if (document.addEventListener) {
    document.addEventListener('DOMContentLoaded', fn);
  } else {
    document.attachEvent('onreadystatechange', function() {
      if (document.readyState != 'loading')

example inline usage:

ready(function() { alert('hello'); });

JavaScript: Create and destroy class instance through class method

You can only manually delete properties of objects. Thus:

var container = {};

container.instance = new class();

delete container.instance;

However, this won't work on any other pointers. Therefore:

var container = {};

container.instance = new class();

var pointer = container.instance;

delete pointer; // false ( ie attempt to delete failed )


delete container.instance; // true ( ie attempt to delete succeeded, but... )

pointer; // class { destroy: function(){} }

So in practice, deletion is only useful for removing object properties themselves, and is not a reliable method for removing the code they point to from memory.

A manually specified destroy method could unbind any event listeners. Something like:

function class(){ = { /**/ }

  function handler(){ /**/ }

  something.addEventListener( 'event', handler, false );

  this.destroy = function(){
    something.removeEventListener( 'event', handler );

Vue.js: Conditional class style binding

the problem is blade, try this

<i class="fa" v-bind:class="['{{content['cravings']}}' ? 'fa-checkbox-marked' : 'fa-checkbox-blank-outline']"></i>

Change image source with JavaScript

The problem was that you were using .src without needing it and you also needed to differentiate which img you wanted to change.

function changeImage(a, imgid) {
<div id="main_img">
    <img id="img" src="1772031_29_b.jpg">
<div id="thumb_img">
    <img id="1" src='1772031_29_t.jpg'  onclick='changeImage("1772031_29_b.jpg", "1");'>
    <img id="2" src='1772031_55_t.jpg'  onclick='changeImage("1772031_55_b.jpg", "2");'>
    <img id="3" src='1772031_53_t.jpg'  onclick='changeImage("1772031_53_b.jpg", "3");'>

websocket.send() parameter

As I understand it, you want the server be able to send messages through from client 1 to client 2. You cannot directly connect two clients because one of the two ends of a WebSocket connection needs to be a server.

This is some pseudocodish JavaScript:


var websocket = new WebSocket("server address");

websocket.onmessage = function(str) {
  console.log("Someone sent: ", str);

// Tell the server this is client 1 (swap for client 2 of course)
  id: "client1"

// Tell the server we want to send something to the other client
  to: "client2",
  data: "foo"


var clients = {};

server.on("data", function(client, str) {
  var obj = JSON.parse(str);

  if("id" in obj) {
    // New client, add it to the id/client object
    clients[] = client;
  } else {
    // Send data to the client requested

Property 'value' does not exist on type EventTarget in TypeScript

I was looking for a solution to a similar TypeScript error with React:

Property 'dataset' does not exist on type EventTarget in TypeScript

I wanted to get to of a clicked button element in React:

  data-name="Foo Bar"
  Delete Candidate

Here is how I was able to get the dataset value to "exist" via TypeScript:

const onClickHandler = (event: React.MouseEvent<HTMLButtonElement>) => {
  const { name, index } = ( as HTMLButtonElement).dataset
  console.log({ name, index })
  // do stuff with name and index…

React Hooks useState() with Object

I think best solution is Immer. It allows you to update object like you are directly modifying fields (masterField.fieldOne.fieldx = 'abc'). But it will not change actual object of course. It collects all updates on a draft object and gives you a final object at the end which you can use to replace original object.

How to detect if JavaScript is disabled?

A common solution is to the meta tag in conjunction with noscript to refresh the page and notify the server when JavaScript is disabled, like this:

<!DOCTYPE html>
<html lang="en">
            <meta http-equiv="refresh" content="0; /?javascript=false">
        <meta charset="UTF-8"/>

In the above example when JavaScript is disabled the browser will redirect to the home page of the web site in 0 seconds. In addition it will also send the parameter javascript=false to the server.

A server side script such as node.js or PHP can then parse the parameter and come to know that JavaScript is disabled. It can then send a special non-JavaScript version of the web site to the client.

How to have jQuery restrict file types on upload?

This example allows to upload PNG image only.


<input type="file" class="form-control" id="FileUpload1" accept="image/png" />


                function () {
                    var fileExtension = ['png'];
                    if ($.inArray($(this).val().split('.').pop().toLowerCase(), fileExtension) == -1) {
                        alert("Only '.png' format is allowed.");
                        this.value = ''; // Clean field
                        return false;

JQuery Redirect to URL after specified time

Yes, the solution is to use setTimeout, like this:

var delay = 10000;
var url = "";
var timeoutID = setTimeout(function() {
    window.location.href = url;
}, delay);

note that the result was stored into timeoutID. If, for whatever reason you need to cancel the order, you just need to call


Check if input value is empty and display an alert

   if($('#myMessage').val() == ''){
      alert('Input can not be left blank');


If you don't want whitespace also u can remove them using jQuery.trim()

Description: Remove the whitespace from the beginning and end of a string.

   if($.trim($('#myMessage').val()) == ''){
      alert('Input can not be left blank');

Validate decimal numbers in JavaScript - IsNumeric()

function isNumber(n) {
    return (n===n+''||n===n-0) && n*0==0 && /\S/.test(n);


(n===n-0||n===n+'') verifies if n is a number or a string (discards arrays, boolean, date, null, ...). You can replace (n===n-0||n===n+'') by n!==undefined && n!==null && (n.constructor===Number||n.constructor===String): significantly faster but less concise.

n*0==0 verifies if n is a finite number as isFinite(n) does. If you need to check strings that represent negative hexadecimal, just replace n*0==0 by something like n.toString().replace(/^\s*-/,'')*0==0.
It costs a little of course, so if you don't need it, don't use it.

/\S/.test(n) discards empty strings or strings, that contain only white-spaces (necessary since isFinite(n) or n*0==0 return a false positive in this case). You can reduce the number of call to .test(n) by using (n!=0||/0/.test(n)) instead of /\S/.test(n), or you can use a slightly faster but less concise test such as (n!=0||(n+'').indexOf('0')>=0): tiny improvement.

Read XML file using javascript

The code below will convert any XMLObject or string to a native JavaScript object. Then you can walk on the object to extract any value you want.

 * Tries to convert a given XML data to a native JavaScript object by traversing the DOM tree.
 * If a string is given, it first tries to create an XMLDomElement from the given string.
 * @param {XMLDomElement|String} source The XML string or the XMLDomElement prefreably which containts the necessary data for the object.
 * @param {Boolean} [includeRoot] Whether the "required" main container node should be a part of the resultant object or not.
 * @return {Object} The native JavaScript object which is contructed from the given XML data or false if any error occured.
Object.fromXML = function( source, includeRoot ) {
    if( typeof source == 'string' )
            if ( window.DOMParser )
                source = ( new DOMParser() ).parseFromString( source, "application/xml" );
            else if( window.ActiveXObject )
                var xmlObject = new ActiveXObject( "Microsoft.XMLDOM" );
                xmlObject.async = false;
                xmlObject.loadXML( source );
                source = xmlObject;
                xmlObject = undefined;
                throw new Error( "Cannot find an XML parser!" );
        catch( error )
            return false;

    var result = {};

    if( source.nodeType == 9 )
        source = source.firstChild;
    if( !includeRoot )
        source = source.firstChild;

    while( source ) {
        if( source.childNodes.length ) {
            if( source.tagName in result ) {
                if( result[source.tagName].constructor != Array ) 
                    result[source.tagName] = [result[source.tagName]];
                result[source.tagName].push( Object.fromXML( source ) );
                result[source.tagName] = Object.fromXML( source );
        } else if( source.tagName )
            result[source.tagName] = source.nodeValue;
        else if( !source.nextSibling ) {
            if( source.nodeValue.clean() != "" ) {
                result = source.nodeValue.clean();
        source = source.nextSibling;
    return result;

String.prototype.clean = function() {
    var self = this;
    return this.replace(/(\r\n|\n|\r)/gm, "").replace(/^\s+|\s+$/g, "");

How do I update/upsert a document in Mongoose?

You were close with

Contact.update({}, contact, {upsert: true}, function(err){...})

but your second parameter should be an object with a modification operator for example

Contact.update({}, {$set: { phone: }}, {upsert: true}, function(err){...})

Align div with fixed position on the right side

make a parent div, in css make it float:right then make the child div's position fixed this will make the div stay in its position at all times and on the right

How to handle anchor hash linking in AngularJS

This is an old post, but I spent a long time researching various solutions so I wanted to share one more simple one. Just adding target="_self" to the <a> tag fixed it for me. The link works and takes me to the proper location on the page.

However, Angular still injects some weirdness with the # in the URL so you may run into trouble using the back button for navigation and such after using this method.

Asynchronous Process inside a javascript for loop

Any recommendation on how to fix this?

Several. You can use bind:

for (i = 0; i < j; i++) {
    asycronouseProcess(function (i) {
    }.bind(null, i));

Or, if your browser supports let (it will be in the next ECMAScript version, however Firefox already supports it since a while) you could have:

for (i = 0; i < j; i++) {
    let k = i;
    asycronouseProcess(function() {

Or, you could do the job of bind manually (in case the browser doesn't support it, but I would say you can implement a shim in that case, it should be in the link above):

for (i = 0; i < j; i++) {
    asycronouseProcess(function(i) {
        return function () {

I usually prefer let when I can use it (e.g. for Firefox add-on); otherwise bind or a custom currying function (that doesn't need a context object).

How do I preserve line breaks when getting text from a textarea?

The target container should have the white-space:pre style. Try it below.

function copycontent(){_x000D_
 var content = document.getElementById('ta').value;_x000D_
 document.getElementById('target').innerText = content;_x000D_
<textarea id='ta' rows='3'>_x000D_
  line 1_x000D_
  line 2_x000D_
  line 3_x000D_
<button id='btn' onclick='copycontent();'>_x000D_
<p id='target' style='white-space:pre'>_x000D_

What is the difference between typeof and instanceof and when should one be used vs. the other?

Coming from a strict OO upbringing I'd go for

callback instanceof Function

Strings are prone to either my awful spelling or other typos. Plus I feel it reads better.

Passing environment-dependent variables in webpack

There are two basic ways to achieve this.


new webpack.DefinePlugin({
    'process.env.NODE_ENV': JSON.stringify(process.env.NODE_ENV || 'development')

Note that this will just replace the matches "as is". That's why the string is in the format it is. You could have a more complex structure, such as an object there but you get the idea.


new webpack.EnvironmentPlugin(['NODE_ENV'])

EnvironmentPlugin uses DefinePlugin internally and maps the environment values to code through it. Terser syntax.


Alternatively you could consume configuration through an aliased module. From consumer side it would look like this:

var config = require('config');

Configuration itself could look like this:

resolve: {
    alias: {
        config: path.join(__dirname, 'config', process.env.NODE_ENV)

Let's say process.env.NODE_ENV is development. It would map into ./config/development.js then. The module it maps to can export configuration like this:

module.exports = {
    testing: 'something',

split string only on first instance of specified character

What do you need regular expressions and arrays for?

myString = myString.substring(myString.indexOf('_')+1)

var myString= "hello_there_how_are_you"_x000D_
myString = myString.substring(myString.indexOf('_')+1)_x000D_

How to read an external local JSON file in JavaScript?

One simple workaround is to put your JSON file inside a locally running server. for that from the terminal go to your project folder and start the local server on some port number e.g 8181

python -m SimpleHTTPServer 8181

Then browsing to http://localhost:8181/ should display all of your files including the JSON. Remember to install python if you don't already have.

Adding click event for a button created dynamically using jQuery

Question 1: Use .delegate on the div to bind a click handler to the button.

Question 2: Use $(this).val() or this.value (the latter would be faster) inside of the click handler. this will refer to the button.

$("#pg_menu_content").on('click', '#btn_a', function () {

$div = $('<div data-role="fieldcontain"/>');
$("<input type='button' value='Dynamic Button' id='btn_a' />").appendTo($div.clone()).appendTo('#pg_menu_content');

Hide HTML element by id

I found that the following code, when inserted into the site's footer, worked well enough:

<script type="text/javascript">

This may or may not require jquery. The site I'm editing has jquery, but unfortunately I'm no javascripter, so I only have a limited knowledge of what's going on here, and the requirements of this code snippet...

No 'Access-Control-Allow-Origin' header is present on the requested resource—when trying to get data from a REST API

In my case,I use the below solution

Front-end or Angular

    this.serverUrl, dataObjToPost,
      headers: new HttpHeaders({
           'Content-Type':  'application/json',

back-end (I use php)

header("Access-Control-Allow-Origin: http://localhost:4200");
header('Access-Control-Allow-Methods: GET, POST, OPTIONS');
header("Access-Control-Allow-Headers: Content-Type, Authorization");

$postdata = file_get_contents("php://input");
$request = json_decode($postdata);

URL encode sees “&” (ampersand) as “&amp;” HTML entity

If you did literally this:


Then the result is %26, you can test it here. Make sure the string you are encoding is just & and not &amp; to begin with...otherwise it is encoding correctly, which is likely the case. If you need a different result for some reason, you can do a .replace(/&amp;/g,'&') before the encoding.

how to draw smooth curve through N points using javascript HTML5 canvas?

As Daniel Howard points out, Rob Spencer describes what you want at

Here's an interactive demo:

Here it is as a snippet in case jsbin is down.

<!DOCTYPE html>_x000D_
        <meta charset=utf-8 />_x000D_
        <title>Demo smooth connection</title>_x000D_
        <div id="display">_x000D_
          Click to build a smooth path. _x000D_
          (See Rob Spencer's <a href="">article</a>)_x000D_
          <br><label><input type="checkbox" id="showPoints" checked> Show points</label>_x000D_
          <br><label><input type="checkbox" id="showControlLines" checked> Show control lines</label>_x000D_
            <input type="range" id="tension" min="-1" max="2" step=".1" value=".5" > Tension <span id="tensionvalue">(0.5)</span>_x000D_
        <div id="mouse"></div>_x000D_
        <canvas id="canvas"></canvas>_x000D_
          html { position: relative; height: 100%; width: 100%; }_x000D_
          body { position: absolute; left: 0; right: 0; top: 0; bottom: 0; } _x000D_
          canvas { outline: 1px solid red; }_x000D_
          #display { position: fixed; margin: 8px; background: white; z-index: 1; }_x000D_
          function update() {_x000D_
          $("showPoints").onchange = $("showControlLines").onchange = $("tension").onchange = update;_x000D_
          // utility function_x000D_
          function $(id){ return document.getElementById(id); }_x000D_
          var canvas=$("canvas"), ctx=canvas.getContext("2d");_x000D_
          function setCanvasSize() {_x000D_
            canvas.width = parseInt(window.getComputedStyle(document.body).width);_x000D_
            canvas.height = parseInt(window.getComputedStyle(document.body).height);_x000D_
          window.onload = window.onresize = setCanvasSize();_x000D_
          function mousePositionOnCanvas(e) {_x000D_
            var, c=el;_x000D_
            var scaleX = c.width/c.offsetWidth || 1;_x000D_
            var scaleY = c.height/c.offsetHeight || 1;_x000D_
            if (!isNaN(e.offsetX)) _x000D_
              return { x:e.offsetX*scaleX, y:e.offsetY*scaleY };_x000D_
            var x=e.pageX, y=e.pageY;_x000D_
            do {_x000D_
              x -= el.offsetLeft;_x000D_
              y -= el.offsetTop;_x000D_
              el = el.offsetParent;_x000D_
            } while (el);_x000D_
            return { x: x*scaleX, y: y*scaleY };_x000D_
          canvas.onclick = function(e){_x000D_
            var p = mousePositionOnCanvas(e);_x000D_
            addSplinePoint(p.x, p.y);_x000D_
          function drawPoint(x,y,color){_x000D_
          canvas.onmousemove = function(e) {_x000D_
            var p = mousePositionOnCanvas(e);_x000D_
            $("mouse").innerHTML = p.x+","+p.y;_x000D_
          var pts=[]; // a list of x and ys_x000D_
          // given an array of x,y's, return distance between any two,_x000D_
          // note that i and j are indexes to the points, not directly into the array._x000D_
          function dista(arr, i, j) {_x000D_
            return Math.sqrt(Math.pow(arr[2*i]-arr[2*j], 2) + Math.pow(arr[2*i+1]-arr[2*j+1], 2));_x000D_
          // return vector from i to j where i and j are indexes pointing into an array of points._x000D_
          function va(arr, i, j){_x000D_
            return [arr[2*j]-arr[2*i], arr[2*j+1]-arr[2*i+1]]_x000D_
          function ctlpts(x1,y1,x2,y2,x3,y3) {_x000D_
            var t = $("tension").value;_x000D_
            var v = va(arguments, 0, 2);_x000D_
            var d01 = dista(arguments, 0, 1);_x000D_
            var d12 = dista(arguments, 1, 2);_x000D_
            var d012 = d01 + d12;_x000D_
            return [x2 - v[0] * t * d01 / d012, y2 - v[1] * t * d01 / d012,_x000D_
                    x2 + v[0] * t * d12 / d012, y2 + v[1] * t * d12 / d012 ];_x000D_
          function addSplinePoint(x, y){_x000D_
            pts.push(x); pts.push(y);_x000D_
          function drawSplines() {_x000D_
            cps = []; // There will be two control points for each "middle" point, 1 ... len-2e_x000D_
            for (var i = 0; i < pts.length - 2; i += 1) {_x000D_
              cps = cps.concat(ctlpts(pts[2*i], pts[2*i+1], _x000D_
                                      pts[2*i+2], pts[2*i+3], _x000D_
                                      pts[2*i+4], pts[2*i+5]));_x000D_
            if ($("showControlLines").checked) drawControlPoints(cps);_x000D_
            if ($("showPoints").checked) drawPoints(pts);_x000D_
            drawCurvedPath(cps, pts);_x000D_
          function drawControlPoints(cps) {_x000D_
            for (var i = 0; i < cps.length; i += 4) {_x000D_
              showPt(cps[i], cps[i+1], "pink");_x000D_
              showPt(cps[i+2], cps[i+3], "pink");_x000D_
              drawLine(cps[i], cps[i+1], cps[i+2], cps[i+3], "pink");_x000D_
            } _x000D_
          function drawPoints(pts) {_x000D_
            for (var i = 0; i < pts.length; i += 2) {_x000D_
              showPt(pts[i], pts[i+1], "black");_x000D_
            } _x000D_
          function drawCurvedPath(cps, pts){_x000D_
            var len = pts.length / 2; // number of points_x000D_
            if (len < 2) return;_x000D_
            if (len == 2) {_x000D_
              ctx.moveTo(pts[0], pts[1]);_x000D_
              ctx.lineTo(pts[2], pts[3]);_x000D_
            else {_x000D_
              ctx.moveTo(pts[0], pts[1]);_x000D_
              // from point 0 to point 1 is a quadratic_x000D_
              ctx.quadraticCurveTo(cps[0], cps[1], pts[2], pts[3]);_x000D_
              // for all middle points, connect with bezier_x000D_
              for (var i = 2; i < len-1; i += 1) {_x000D_
                // console.log("to", pts[2*i], pts[2*i+1]);_x000D_
                  cps[(2*(i-1)-1)*2], cps[(2*(i-1)-1)*2+1],_x000D_
                  cps[(2*(i-1))*2], cps[(2*(i-1))*2+1],_x000D_
                  pts[i*2], pts[i*2+1]);_x000D_
                cps[(2*(i-1)-1)*2], cps[(2*(i-1)-1)*2+1],_x000D_
                pts[i*2], pts[i*2+1]);_x000D_
          function clear() {_x000D_
            // use alpha to fade out_x000D_
            ctx.fillStyle = "rgba(255,255,255,.7)"; // clear screen_x000D_
          function showPt(x,y,fillStyle) {_x000D_
            if (fillStyle) {_x000D_
              ctx.fillStyle = fillStyle;_x000D_
            ctx.arc(x, y, 5, 0, 2*Math.PI);_x000D_
          function drawLine(x1, y1, x2, y2, strokeStyle){_x000D_
            ctx.moveTo(x1, y1);_x000D_
            ctx.lineTo(x2, y2);_x000D_
            if (strokeStyle) {_x000D_
              ctx.strokeStyle = strokeStyle;_x000D_
            else {_x000D_
              ctx.strokeStyle = "pink";_x000D_

How to trigger the window resize event in JavaScript?

window.resizeBy() will trigger window's onresize event. This works in both Javascript or VBScript.

window.resizeBy(xDelta, yDelta) called like window.resizeBy(-200, -200) to shrink page 200px by 200px.

Javascript Get Element by Id and set the value

If myFunc(variable) is executed before textarea is rendered to page, you will get the null exception error.

    <script type="text/javascript">
        function myFunc(variable){
            var s = document.getElementById(variable);
            s.value = "new value";
        <textarea id="id1"></textarea>
//Error message: Cannot set property 'value' of null 

So, make sure your textarea does exist in the page, and then call myFunc, you can use window.onload or $(document).ready function. Hope it's helpful.

How to get the innerHTML of selectable jquery element?

The parameter ui has a property called selected which is a reference to the selected dom element, you can call innerHTML on that element.

Your code $('.ui-selected').innerHTML tries to return the innerHTML property of a jQuery wrapper element for a dom element with class ui-selected

$(function () {
        selected: function (event, ui) {
            var $variable = ui.selected.innerHTML; // or $(ui.selected).html()

Demo: Fiddle

Cannot read property 'style' of undefined -- Uncaught Type Error

It's currently working, I've just changed the operator > in order to work in the snippet, take a look:

window.onload = function() {_x000D_
  if (window.location.href.indexOf("test") <= -1) {_x000D_
    var search_span = document.getElementsByClassName("securitySearchQuery");_x000D_
    search_span[0].style.color = "blue";_x000D_
    search_span[0].style.fontWeight = "bold";_x000D_
    search_span[0].style.fontSize = "40px";_x000D_
<h1 class="keyword-title">Search results for<span class="securitySearchQuery"> "hi".</span></h1>

What is a good regular expression to match a URL?

These are the droids you're looking for. This is taken from validator.js which is the library you should really use to do this. But if you want to roll your own, who am I to stop you? If you want pure regex then you can just take out the length check. I think it's a good idea to test the length of the URL though if you really want to determine compliance with the spec.

 function isURL(str) {
     var urlRegex = '^(?!mailto:)(?:(?:http|https|ftp)://)(?:\\S+(?::\\S*)?@)?(?:(?:(?:[1-9]\\d?|1\\d\\d|2[01]\\d|22[0-3])(?:\\.(?:1?\\d{1,2}|2[0-4]\\d|25[0-5])){2}(?:\\.(?:[0-9]\\d?|1\\d\\d|2[0-4]\\d|25[0-4]))|(?:(?:[a-z\\u00a1-\\uffff0-9]+-?)*[a-z\\u00a1-\\uffff0-9]+)(?:\\.(?:[a-z\\u00a1-\\uffff0-9]+-?)*[a-z\\u00a1-\\uffff0-9]+)*(?:\\.(?:[a-z\\u00a1-\\uffff]{2,})))|localhost)(?::\\d{2,5})?(?:(/|\\?|#)[^\\s]*)?$';
     var url = new RegExp(urlRegex, 'i');
     return str.length < 2083 && url.test(str);

jquery get all input from specific form

To iterate through all the inputs in a form you can do this:

$("form#formID :input").each(function(){
 var input = $(this); // This is the jquery object of the input, do what you will

This uses the jquery :input selector to get ALL types of inputs, if you just want text you can do :

$("form#formID input[type=text]")//...


What is the $$hashKey added to my JSON.stringify result

In my use case (feeding the resulting object to X2JS) the recommended approach

data = angular.toJson(source);

help to remove the $$hashKey properties, but the result could then no longer be processed by X2JS.

data = angular.copy(source);

removed the $$hashKey properties as well, but the result remained usable as a parameter for X2JS.

JavaScript blob filename without link

This is my solution. From my point of view, you can not bypass the <a>.

function export2json() {_x000D_
  const data = {_x000D_
    a: '111',_x000D_
    b: '222',_x000D_
    c: '333'_x000D_
  const a = document.createElement("a");_x000D_
  a.href = URL.createObjectURL(_x000D_
    new Blob([JSON.stringify(data, null, 2)], {_x000D_
      type: "application/json"_x000D_
  a.setAttribute("download", "data.json");_x000D_
<button onclick="export2json()">Export data to json file</button>

Test if something is not undefined in JavaScript

Check if condition == null; It will resolve the problem

jQuery ajax success callback function definition

I do not know why you are defining the parameter outside the script. That is unnecessary. Your callback function will be called with the return data as a parameter automatically. It is very possible to define your callback outside the sucess: i.e.

function getData() {
        url : '',
        type: 'GET',
        success : handleData

function handleData(data) {
    //do some stuff

the handleData function will be called and the parameter passed to it by the ajax function.

react-router getting this.props.location in child components

If the above solution didn't work for you, you can use import { withRouter } from 'react-router-dom';

Using this you can export your child class as -

class MyApp extends Component{
    // your code

export default withRouter(MyApp);

And your class with Router -

// your code
      <Route path="/myapp" component={MyApp} />
      // or if you are sending additional fields
      <Route path="/myapp" component={() =><MyApp process={...} />} />

Format date with Moment.js

May be this helps some one who are looking for multiple date formats one after the other by willingly or unexpectedly. Please find the code: I am using moment.js format function on a current date as (today is 29-06-2020) var startDate = moment(new Date()).format('MM/DD/YY'); Result: 06/28/20

what happening is it retains only the year part :20 as "06/28/20", after If I run the statement : new Date(startDate) The result is "Mon Jun 28 1920 00:00:00 GMT+0530 (India Standard Time)",

Then, when I use another format on "06/28/20": startDate = moment(startDate ).format('MM-DD-YYYY'); Result: 06-28-1920, in google chrome and firefox browsers it gives correct date on second attempt as: 06-28-2020. But in IE it is having issues, from this I understood we can apply one dateformat on the given date, If we want second date format, it should be apply on the fresh date not on the first date format result. And also observe that for first time applying 'MM-DD-YYYY' and next 'MM-DD-YY' is working in IE. For clear understanding please find my question in the link: Date went wrong when using Momentjs date format in IE 11

How to calculate number of days between two dates

I made a quick re-usable function in ES6 using Moment.js.

const getDaysDiff = (start_date, end_date, date_format = 'YYYY-MM-DD') => {_x000D_
  const getDateAsArray = (date) => {_x000D_
    return moment(date.split(/\D+/), date_format);_x000D_
  return getDateAsArray(end_date).diff(getDateAsArray(start_date), 'days') + 1;_x000D_
console.log(getDaysDiff('2019-10-01', '2019-10-30'));_x000D_
console.log(getDaysDiff('2019/10/01', '2019/10/30'));_x000D_
console.log(getDaysDiff('2019.10-01', '2019.10 30'));_x000D_
console.log(getDaysDiff('2019 10 01', '2019 10 30'));_x000D_
console.log(getDaysDiff('+++++2019!!/###10/$$01', '2019-10-30'));_x000D_
console.log(getDaysDiff('2019-10-01-2019', '2019-10-30'));_x000D_
console.log(getDaysDiff('10-01-2019', '10-30-2019', 'MM-DD-YYYY'));_x000D_
console.log(getDaysDiff('10-01-2019', '10-30-2019'));_x000D_
console.log(getDaysDiff('10-01-2019', '2019-10-30', 'MM-DD-YYYY'));
<script src=""></script>

JavaScript Nested function

It is called closure.

Basically, the function defined within other function is accessible only within this function. But may be passed as a result and then this result may be called.

It is a very powerful feature. You can see more explanation here:

javascript_closures_for_dummies.html mirror on

Sort JavaScript object by key

As already mentioned, objects are unordered.


You may find this idiom useful:

var o = { 'b' : 'asdsad', 'c' : 'masdas', 'a' : 'dsfdsfsdf' };

var kv = [];

for (var k in o) {
  kv.push([k, o[k]]);


You can then iterate through kv and do whatever you wish.

> kv.sort()
[ [ 'a', 'dsfdsfsdf' ],
  [ 'b', 'asdsad' ],
  [ 'c', 'masdas' ] ]

How to implement "select all" check box in HTML?

This is what this will do, for instance if you have 5 checkboxes, and you click check all,it check all, now if you uncheck all the checkbox probably by clicking each 5 checkboxs, by the time you uncheck the last checkbox, the select all checkbox also gets unchecked

   $(".allcheckbox").prop("checked", $(this).prop("checked"))
      if($(this).prop("checked") == false){
          $("#select-all").prop("checked", false)
      if($(".allcheckbox:checked").length == $(".allcheckbox").length){
          $("#select-all").prop("checked", true)

Alter and Assign Object Without Side Effects

You either need to keep creating new objects, or clone the existing one. See What is the most efficient way to deep clone an object in JavaScript? for how to clone.

Why is my toFixed() function not working?

Your conversion data is response[25] and follow the below steps.

var i = parseFloat(response[25]).toFixed(2)

how to remove json object key and value.?

There are several ways to do this, lets see them one by one:

  1. delete method: The most common way

const myObject = {_x000D_
    "employeeid": "160915848",_x000D_
    "firstName": "tet",_x000D_
    "lastName": "test",_x000D_
    "email": "[email protected]",_x000D_
    "country": "Brasil",_x000D_
    "currentIndustry": "aaaaaaaaaaaaa",_x000D_
    "otherIndustry": "aaaaaaaaaaaaa",_x000D_
    "currentOrganization": "test",_x000D_
    "salary": "1234567"_x000D_
delete myObject['currentIndustry'];_x000D_
// OR delete myObject.currentIndustry;_x000D_

  1. By making key value undefined: Alternate & a faster way:

let myObject = {_x000D_
    "employeeid": "160915848",_x000D_
    "firstName": "tet",_x000D_
    "lastName": "test",_x000D_
    "email": "[email protected]",_x000D_
    "country": "Brasil",_x000D_
    "currentIndustry": "aaaaaaaaaaaaa",_x000D_
    "otherIndustry": "aaaaaaaaaaaaa",_x000D_
    "currentOrganization": "test",_x000D_
    "salary": "1234567"_x000D_
myObject.currentIndustry = undefined;_x000D_
myObject = JSON.parse(JSON.stringify(myObject));_x000D_

  1. With es6 spread Operator:

const myObject = {_x000D_
    "employeeid": "160915848",_x000D_
    "firstName": "tet",_x000D_
    "lastName": "test",_x000D_
    "email": "[email protected]",_x000D_
    "country": "Brasil",_x000D_
    "currentIndustry": "aaaaaaaaaaaaa",_x000D_
    "otherIndustry": "aaaaaaaaaaaaa",_x000D_
    "currentOrganization": "test",_x000D_
    "salary": "1234567"_x000D_
const {currentIndustry, ...filteredObject} = myObject;_x000D_

Or if you can use omit() of underscore js library:

const filteredObject = _.omit(currentIndustry, 'myObject');

When to use what??

If you don't wanna create a new filtered object, simply go for either option 1 or 2. Make sure you define your object with let while going with the second option as we are overriding the values. Or else you can use any of them.

hope this helps :)

How to validate a file upload field using Javascript/jquery

Check it's value property:

In jQuery (since your tag mentions it):


Or in vanilla JavaScript:


JavaScript load a page on button click

Just window.location = "", or, for local links, window.location = "my_relative_link.html".

You can try it by typing it into your address bar as well, e.g. javascript: window.location = "".

Also note that the protocol part of the URL (http://) is not optional for absolute links; omitting it will make javascript assume a relative link.

Html.Partial vs Html.RenderPartial & Html.Action vs Html.RenderAction

Difference is first one returns an MvcHtmlString but second (Render..) outputs straight to the response.

The POM for project is missing, no dependency information available

The scope <scope>provided</scope> gives you an opportunity to tell that the jar would be available at runtime, so do not bundle it. It does not mean that you do not need it at compile time, hence maven would try to download that.

Now I think, the below maven artifact do not exist at all. I tries searching google, but not able to find. Hence you are getting this issue.

Change groupId to <groupId>net.sourceforge.ant4x</groupId> to get the latest jar.


Another solution for this problem is:

  1. Run your own maven repo.
  2. download the jar
  3. Install the jar into the repository.
  4. Add a code in your pom.xml something like:

Where http://localhost/repo is your local repo URL:

    <-- Other repository config ... -->

pycharm running way slow

In my case, it was very slow and i needed to change inspections settings, i tried everything, the only thing that worked was going from 2018.2 version to 2016.2, sometimes is better to be some updates behind...

how to kill hadoop jobs

Run list to show all the jobs, then use the jobID/applicationID in the appropriate command.

Kill mapred jobs:

mapred job -list
mapred job -kill <jobId>

Kill yarn jobs:

yarn application -list
yarn application -kill <ApplicationId>

check null,empty or undefined angularjs

You can use angular's function called angular.isUndefined(value) returns boolean.

You may read more about angular's functions here: AngularJS Functions (isUndefined)

How to get default gateway in Mac OSX

You can try with:

route -n get default

It is not the same as GNU/Linux's route -n (or even ip route show) but is useful for checking the default route information. Also, you can check the route that packages will take to a particular host. E.g.

route -n get

The output would be similar to:

   route to:
destination: default
  interface: tun0
 recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu     expire
       0         0         0         0         0         0      1500         0

IMHO netstat -nr is what you need. Even MacOSX's Network utility app(*) uses the output of netstat to show routing information. Network utility screenshot displaying routing table information

I hope this helps :)

(*) You can start Network utility with open /Applications/Utilities/Network\

How to record phone calls in android?

Ok, for this first of all you need to use Device Policy Manager, and need to make your device Admin device. After that you have to create one BroadCast receiver and one service. I am posting code here and its working fine.


public class MainActivity extends Activity {
    private static final int REQUEST_CODE = 0;
    private DevicePolicyManager mDPM;
    private ComponentName mAdminName;

    protected void onCreate(Bundle savedInstanceState) {

        try {
            // Initiate DevicePolicyManager.
            mDPM = (DevicePolicyManager) getSystemService(Context.DEVICE_POLICY_SERVICE);
            mAdminName = new ComponentName(this, DeviceAdminDemo.class);

            if (!mDPM.isAdminActive(mAdminName)) {
                Intent intent = new Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
                intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, mAdminName);
                intent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION, "Click on Activate button to secure your application.");
                startActivityForResult(intent, REQUEST_CODE);
            } else {
                // mDPM.lockNow();
                // Intent intent = new Intent(MainActivity.this,
                // TrackDeviceService.class);
                // startService(intent);
        } catch (Exception e) {

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (REQUEST_CODE == requestCode) {
                Intent intent = new Intent(MainActivity.this, TService.class);


//DeviceAdminDemo class

public class DeviceAdminDemo extends DeviceAdminReceiver {
    public void onReceive(Context context, Intent intent) {
        super.onReceive(context, intent);

    public void onEnabled(Context context, Intent intent) {

    public void onDisabled(Context context, Intent intent) {

//TService Class

public class TService extends Service {
    MediaRecorder recorder;
    File audiofile;
    String name, phonenumber;
    String audio_format;
    public String Audio_Type;
    int audioSource;
    Context context;
    private Handler handler;
    Timer timer;
    Boolean offHook = false, ringing = false;
    Toast toast;
    Boolean isOffHook = false;
    private boolean recordstarted = false;

    private static final String ACTION_IN = "android.intent.action.PHONE_STATE";
    private static final String ACTION_OUT = "android.intent.action.NEW_OUTGOING_CALL";
    private CallBr br_call;

    public IBinder onBind(Intent arg0) {
        // TODO Auto-generated method stub
        return null;

    public void onDestroy() {
        Log.d("service", "destroy");


    public int onStartCommand(Intent intent, int flags, int startId) {
        // final String terminate =(String)
        // intent.getExtras().get("terminate");//
        // intent.getStringExtra("terminate");
        // Log.d("TAG", "service started");
        // TelephonyManager telephony = (TelephonyManager)
        // getSystemService(Context.TELEPHONY_SERVICE); // TelephonyManager
        // // object
        // CustomPhoneStateListener customPhoneListener = new
        // CustomPhoneStateListener();
        // telephony.listen(customPhoneListener,
        // PhoneStateListener.LISTEN_CALL_STATE);
        // context = getApplicationContext();

        final IntentFilter filter = new IntentFilter();
        this.br_call = new CallBr();
        this.registerReceiver(this.br_call, filter);

        // if(terminate != null) {
        // stopSelf();
        // }
        return START_NOT_STICKY;

    public class CallBr extends BroadcastReceiver {
        Bundle bundle;
        String state;
        String inCall, outCall;
        public boolean wasRinging = false;

        public void onReceive(Context context, Intent intent) {
            if (intent.getAction().equals(ACTION_IN)) {
                if ((bundle = intent.getExtras()) != null) {
                    state = bundle.getString(TelephonyManager.EXTRA_STATE);
                    if (state.equals(TelephonyManager.EXTRA_STATE_RINGING)) {
                        inCall = bundle.getString(TelephonyManager.EXTRA_INCOMING_NUMBER);
                        wasRinging = true;
                        Toast.makeText(context, "IN : " + inCall, Toast.LENGTH_LONG).show();
                    } else if (state.equals(TelephonyManager.EXTRA_STATE_OFFHOOK)) {
                        if (wasRinging == true) {

                            Toast.makeText(context, "ANSWERED", Toast.LENGTH_LONG).show();

                            String out = new SimpleDateFormat("dd-MM-yyyy hh-mm-ss").format(new Date());
                            File sampleDir = new File(Environment.getExternalStorageDirectory(), "/TestRecordingDasa1");
                            if (!sampleDir.exists()) {
                            String file_name = "Record";
                            try {
                                audiofile = File.createTempFile(file_name, ".amr", sampleDir);
                            } catch (IOException e) {
                            String path = Environment.getExternalStorageDirectory().getAbsolutePath();

                            recorder = new MediaRecorder();
//                          recorder.setAudioSource(MediaRecorder.AudioSource.VOICE_CALL);

                            try {
                            } catch (IllegalStateException e) {
                            } catch (IOException e) { 
                            recordstarted = true;
                    } else if (state.equals(TelephonyManager.EXTRA_STATE_IDLE)) {
                        wasRinging = false;
                        Toast.makeText(context, "REJECT || DISCO", Toast.LENGTH_LONG).show();
                        if (recordstarted) {
                            recordstarted = false;
            } else if (intent.getAction().equals(ACTION_OUT)) {
                if ((bundle = intent.getExtras()) != null) {
                    outCall = intent.getStringExtra(Intent.EXTRA_PHONE_NUMBER);
                    Toast.makeText(context, "OUT : " + outCall, Toast.LENGTH_LONG).show();


//Permission in manifest file

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.RECORD_AUDIO" />
    <uses-permission android:name="android.permission.PROCESS_OUTGOING_CALLS" />
    <uses-permission android:name="android.permission.READ_PHONE_STATE" />
    <uses-permission android:name="android.permission.STORAGE" />


<device-admin xmlns:android="" >
        <force-lock />

//Declare following thing in manifest:

Declare DeviceAdminDemo class to manifest:

            android:permission="android.permission.BIND_DEVICE_ADMIN" >
                android:resource="@xml/my_admin" />

                <action android:name="" />
                <action android:name="" />
                <action android:name="" />

<service android:name=".TService" >

StringIO in Python3

Thank you OP for your question, and Roman for your answer. I had to search a bit to find this; I hope the following helps others.

Python 2.7


import numpy as np
from StringIO import StringIO

data = "1, abc , 2\n 3, xxx, 4"

print type(data)
<type 'str'>

print '\n', np.genfromtxt(StringIO(data), delimiter=",", dtype="|S3", autostrip=True)
[['1' 'abc' '2']
 ['3' 'xxx' '4']]

print '\n', type(data)
<type 'str'>

print '\n', np.genfromtxt(StringIO(data), delimiter=",", autostrip=True)
[[  1.  nan   2.]
 [  3.  nan   4.]]

Python 3.5:

import numpy as np
from io import StringIO
import io

data = "1, abc , 2\n 3, xxx, 4"
1, abc , 2
 3, xxx, 4

<class 'str'>

#np.genfromtxt(StringIO(data), delimiter=",", autostrip=True)
# TypeError: Can't convert 'bytes' object to str implicitly

print(np.genfromtxt(io.BytesIO(data.encode()), delimiter=",", dtype="|S3", autostrip=True))
[[b'1' b'abc' b'2']
 [b'3' b'xxx' b'4']]

print(np.genfromtxt(io.BytesIO(data.encode()), delimiter=",", autostrip=True))
[[  1.  nan   2.]
 [  3.  nan   4.]]


dtype="|Sx", where x = any of { 1, 2, 3, ...}:

dtypes. Difference between S1 and S2 in Python

"The |S1 and |S2 strings are data type descriptors; the first means the array holds strings of length 1, the second of length 2. ..."

Python loop to run for certain amount of seconds

For those using asyncio, an easy way is to use asyncio.wait_for():

async def my_loop():
    res = False
    while not res:
        res = await do_something()

await asyncio.wait_for(my_loop(), 10)

virtualbox Raw-mode is unavailable courtesy of Hyper-V windows 10

i had same problem guys

virtual box was running smoothly on my windows machine but when new update came virtual started giving me this error and believe me guys just a little S%$& thing fixed it

in my case this problem fixed just by installing windows extension pack that's it

c# open a new form then close the current form?

You weren't specific, but it looks like you were trying to do what I do in my Win Forms apps: start with a Login form, then after successful login, close that form and put focus on a Main form. Here's how I do it:

  1. make frmMain the startup form; this is what my Program.cs looks like:

    static void Main()
        Application.Run(new frmMain());
  2. in my frmLogin, create a public property that gets initialized to false and set to true only if a successful login occurs:

    public bool IsLoggedIn { get; set; }
  3. my frmMain looks like this:

    private void frmMain_Load(object sender, EventArgs e)
        frmLogin frm = new frmLogin();
        frm.IsLoggedIn = false;
        if (!frm.IsLoggedIn)

No successful login? Exit the application. Otherwise, carry on with frmMain. Since it's the startup form, when it closes, the application ends.

ORA-12505, TNS:listener does not currently know of SID given in connect descriptor

I was just creating the database link incorrectly.

Simple fix for me was to simply change 'SID' to SERVICE_NAME






resolved my issue.

How to embed matplotlib in pyqt - for Dummies

For those looking for a dynamic solution to embed Matplotlib in PyQt5 (even plot data using drag and drop). In PyQt5 you need to use super on the main window class to accept the drops. The dropevent function can be used to get the filename and rest is simple:

def dropEvent(self,e):
        This function will enable the drop file directly on to the 
        main window. The file location will be stored in the self.filename
        if e.mimeData().hasUrls:
            for url in e.mimeData().urls():
                if op_sys == 'Darwin':
                    fname = str(NSURL.URLWithString_(str(url.toString())).filePathURL().path())
                    fname = str(url.toLocalFile())
            self.filename = fname
            print("GOT ADDRESS:",self.filename)
            e.ignore() # just like above functions  

For starters the reference complete code gives this output: enter image description here

T-SQL CASE Clause: How to specify WHEN NULL

Jason caught an error, so this works...

Can anyone confirm the other platform versions?
SQL Server:

CASE LEN(ISNULL(last_name,'')) 
ELSE ' ' + last_name
END AS newlastName


CASE LENGTH(IFNULL(last_name,'')) 
ELSE ' ' + last_name
END AS newlastName


CASE LENGTH(NVL(last_name,'')) 
ELSE ' ' + last_name
END AS newlastName

Byte Array to Image object

Since it sounds like you already know what format the byte[] array is in (e.g. RGB, ARGB, BGR etc.) you might be able to use BufferedImage.setRGB(...), or a combination of BufferedImage.getRaster() and WritableRaster.setPixels(...) or WritableRaster.setSamples(...). Unforunately both of these methods require you transform your byte[] into one of int[], float[] or double[] depending on the image format.

Sending SOAP request using Python Requests

It is indeed possible.

Here is an example calling the Weather SOAP Service using plain requests lib:

import requests
#headers = {'content-type': 'application/soap+xml'}
headers = {'content-type': 'text/xml'}
body = """<?xml version="1.0" encoding="UTF-8"?>
         <SOAP-ENV:Envelope xmlns:ns0="" xmlns:ns1="" 
            xmlns:xsi="" xmlns:SOAP-ENV="">

response =,data=body,headers=headers)
print response.content

Some notes:

  • The headers are important. Most SOAP requests will not work without the correct headers. application/soap+xml is probably the more correct header to use (but the weatherservice prefers text/xml
  • This will return the response as a string of xml - you would then need to parse that xml.
  • For simplicity I have included the request as plain text. But best practise would be to store this as a template, then you can load it using jinja2 (for example) - and also pass in variables.

For example:

from jinja2 import Environment, PackageLoader
env = Environment(loader=PackageLoader('myapp', 'templates'))
template = env.get_template('soaprequests/WeatherSericeRequest.xml')
body = template.render()

Some people have mentioned the suds library. Suds is probably the more correct way to be interacting with SOAP, but I often find that it panics a little when you have WDSLs that are badly formed (which, TBH, is more likely than not when you're dealing with an institution that still uses SOAP ;) ).

You can do the above with suds like so:

from suds.client import Client
client = Client(url)
print client ## shows the details of this service

result = client.service.GetWeatherInformation() 
print result 

Note: when using suds, you will almost always end up needing to use the doctor!

Finally, a little bonus for debugging SOAP; TCPdump is your friend. On Mac, you can run TCPdump like so:

sudo tcpdump -As 0 

This can be helpful for inspecting the requests that actually go over the wire.

The above two code snippets are also available as gists:

How can I use a C++ library from node.js?

There newer ways to connect Node.js and C++. Please, loot at Nan.

EDIT The fastest and easiest way is nbind. If you want to write asynchronous add-on you can combine Asyncworker class from nan.

What does a question mark represent in SQL queries?

The ? is to allow Parameterized Query. These parameterized query is to allow type-specific value when replacing the ? with their respective value.

That's all to it.

Here's a reason of why it's better to use Parameterized Query. Basically, it's easier to read and debug.

align textbox and text/labels in html?

Using a table would be one (and easy) option.

Other options are all about setting fixed width on the and making it text-aligned to the right:

label {
   width: 200px;
   display: inline-block;
   text-align: right;

or, as was pointed out, make them all float instead of inline.

How can I delete all cookies with JavaScript?

There is no 100% solution to delete browser cookies.

The problem is that cookies are uniquely identified by not just by their key "name" but also their "domain" and "path".

Without knowing the "domain" and "path" of a cookie, you cannot reliably delete it. This information is not available through JavaScript's document.cookie. It's not available through the HTTP Cookie header either!

However, if you know the name, path and domain of a cookie, then you can clear it by setting an empty cookie with an expiry date in the past, for example:

function clearCookie(name, domain, path){
    var domain = domain || document.domain;
    var path = path || "/";
    document.cookie = name + "=; expires=" + +new Date + "; domain=" + domain + "; path=" + path;

How to call code behind server method from a client side JavaScript function?

In my opinion, the solution proposed by user1965719 is really elegant. In my project, all objects going in to the containing div is dynamically created, so adding the extra hidden button is a breeze:

aspx code:

    <asp:Button runat="server" id="btnResponse1" Text="" 
    style="display: none; width:100%; height:100%"
    OnClick="btnResponses_Clicked" />

    <div class="circlebuttontext" id="calendarButtonText">Calendar</div>

C# code behind:

protected void btnResponses_Clicked(object sender, EventArgs e)
    if(sender == btnResponse1)
        //Your code behind logic for that button goes here

Get docker container id from container name

In my case I was running Tensorflow Docker container in Ubuntu 20.04 :Run your docker container in One terminal , I ran it with

docker run -it od

And then started another terminal and ran below docker ps with sudo:

sudo docker ps

I successfully got container id:

CONTAINER ID        IMAGE               COMMAND             CREATED             
STATUS              PORTS               NAMES
e4ca1ad20b84        od                  "/bin/bash"         18 minutes ago      
Up 18 minutes                           unruffled_stonebraker

How to calculate date difference in JavaScript?

based on javascript runtime prototype implementation you can use simple arithmetic to subtract dates as in bellow

var sep = new Date(2020, 07, 31, 23, 59, 59);
var today = new Date();
var diffD = Math.floor((sep - today) / (1000 * 60 * 60 * 24));
console.log('Day Diff: '+diffD);

the difference return answer as milliseconds, then you have to convert it by division:

  • by 1000 to convert to second
  • by 1000×60 convert to minute
  • by 1000×60×60 convert to hour
  • by 1000×60×60×24 convert to day

C++ Vector of pointers

I am not sure what the last line means. Does it mean, I read the file, create multiple Movie objects. Then make a vector of pointers where each element (pointer) points to one of those Movie objects?

I would guess this is what is intended. The intent is probably that you read the data for one movie, allocate an object with new, fill the object in with the data, and then push the address of the data onto the vector (probably not the best design, but most likely what's intended anyway).

Meaning of @classmethod and @staticmethod for beginner?

One would use @classmethod when he/she would want to change the behaviour of the method based on which subclass is calling the method. remember we have a reference to the calling class in a class method.

While using static you would want the behaviour to remain unchanged across subclasses


class Hero:

  def say_hello():

  def say_class_hello(cls):
        print("Hi Kido")
        print("Hi Princess")

class HeroSon(Hero):
  def say_son_hello(self):
     print("test  hello")

class HeroDaughter(Hero):
  def say_daughter_hello(self):
     print("test  hello daughter")

testson = HeroSon()

testson.say_class_hello() #Output: "Hi Kido"

testson.say_hello() #Outputs: "Helllo..."

testdaughter = HeroDaughter()

testdaughter.say_class_hello() #Outputs: "Hi Princess"

testdaughter.say_hello() #Outputs: "Helllo..."

Swapping two variable value without using third variable

Maybe off topic, but if you know what you are swapping a single variable between two different values, you may be able to do array logic. Each time this line of code is run, it will swap the value between 1 and 2.

n = [2, 1][n - 1]

How can I match on an attribute that contains a certain string?

To add onto bobince's answer... If whatever tool/library you using uses Xpath 2.0, you can also do this:

//*[count(index-of(tokenize(@class, '\s+' ), $classname)) = 1]

count() is apparently needed because index-of() returns a sequence of each index it has a match at in the string.

How to check what version of jQuery is loaded?

As per Template monster blog, typing, these below scripts will give you the version of the jquery in the site you are traversing now.

 1. console.log(jQuery.fn.jquery);
 2. console.log(jQuery().jquery);

Calling a Function defined inside another function in Javascript

You are not calling the function inner, just defining it.

function outer() { 
    function inner() {

    inner(); //Call the inner function


How to force a script reload and re-execute?

Here's a method which is similar to Kelly's but will remove any pre-existing script with the same source, and uses jQuery.

    function reload_js(src) {
        $('script[src="' + src + '"]').remove();
        $('<script>').attr('src', src).appendTo('head');

Note that the 'type' attribute is no longer needed for scripts as of HTML5. (

Easy way to turn JavaScript array into comma-separated list?

Or (more efficiently):

var arr = new Array(3);
arr[0] = "Zero";
arr[1] = "One";
arr[2] = "Two";

document.write(arr); // same as document.write(arr.toString()) in this context

The toString method of an array when called returns exactly what you need - comma-separated list.

How do I count unique visitors to my site?

Here is a nice tutorial, it is what you need. (Source:

Register and show online users and visitors

Count Online users and visitors using a MySQL table

In this tutorial you can learn how to register, to count, and display in your webpage the number of online users and visitors. The principle is this: each user / visitor is registered in a text file or database. Every time a page of the website is accessed, the php script deletes all records older than a certain time (eg 2 minutes), adds the current user / visitor and takes the number of records left to display.

You can store the online users and visitors in a file on the server, or in a MySQL table. In this case, I think that using a text file to add and read the records is faster than storing them into a MySQL table, which requires more requests.

First it's presented the method with recording in a text file on the server, than the method with MySQL table.

To download the files with the scripts presented in this tutorial, click -> Count Online Users and Visitors.

• Both scripts can be included in ".php" files (with include()), or in ".html" files (with <script>), as you can see in the examples presented at the bottom of this page; but the server must run PHP.

Storing online users and visitors in a text file

To add records in a file on the server with PHP you must set CHMOD 0766 (or CHMOD 0777) permissions to that file, so the PHP can write data in it.

  1. Create a text file on your server (for example, named userson.txt) and give it CHMOD 0777 permissions (in your FTP application, right click on that file, choose Properties, then select Read, Write, and Execute options).
  2. Create a PHP file (named usersontxt.php) having the code below, then copy this php file in the same directory as userson.txt.

The code for usersontxt.php;

// Script Online Users and Visitors -
if(!isset($_SESSION)) session_start();        // start Session, if not already started

$filetxt = 'userson.txt';  // the file in which the online users /visitors are stored
$timeon = 120;             // number of secconds to keep a user online
$sep = '^^';               // characters used to separate the user name and date-time
$vst_id = '-vst-';        // an identifier to know that it is a visitor, not logged user

 If you have an user registration script,
 replace $_SESSION['nume'] with the variable in which the user name is stored.
 You can get a free registration script from:

// get the user name if it is logged, or the visitors IP (and add the identifier)

    $uvon = isset($_SESSION['nume']) ? $_SESSION['nume'] : $_SERVER['SERVER_ADDR']. $vst_id;

$rgxvst = '/^([0-9\.]*)'. $vst_id. '/i';         // regexp to recognize the line with visitors
$nrvst = 0;                                       // to store the number of visitors

// sets the row with the current user /visitor that must be added in $filetxt (and current timestamp)

    $addrow[] = $uvon. $sep. time();

// check if the file from $filetxt exists and is writable

    if(is_writable($filetxt)) {
      // get into an array the lines added in $filetxt
      $ar_rows = file($filetxt, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
      $nrrows = count($ar_rows);

            // number of rows

  // if there is at least one line, parse the $ar_rows array

      if($nrrows>0) {
        for($i=0; $i<$nrrows; $i++) {
          // get each line and separate the user /visitor and the timestamp
          $ar_line = explode($sep, $ar_rows[$i]);
      // add in $addrow array the records in last $timeon seconds
          if($ar_line[0]!=$uvon && (intval($ar_line[1])+$timeon)>=time()) {
            $addrow[] = $ar_rows[$i];

$nruvon = count($addrow);                   // total online
$usron = '';                                    // to store the name of logged users
// traverse $addrow to get the number of visitors and users
for($i=0; $i<$nruvon; $i++) {
 if(preg_match($rgxvst, $addrow[$i])) $nrvst++;       // increment the visitors
 else {
   // gets and stores the user's name
   $ar_usron = explode($sep, $addrow[$i]);
   $usron .= '<br/> - <i>'. $ar_usron[0]. '</i>';
$nrusr = $nruvon - $nrvst;              // gets the users (total - visitors)

// the HTML code with data to be displayed
$reout = '<div id="uvon"><h4>Online: '. $nruvon. '</h4>Visitors: '. $nrvst. '<br/>Users: '. $nrusr. $usron. '</div>';

// write data in $filetxt
if(!file_put_contents($filetxt, implode("\n", $addrow))) $reout = 'Error: Recording file not exists, or is not writable';

// if access from <script>, with GET 'uvon=showon', adds the string to return into a JS statement
// in this way the script can also be included in .html files
if(isset($_GET['uvon']) && $_GET['uvon']=='showon') $reout = "document.write('$reout');";

echo $reout;             // output /display the result
  1. If you want to include the script above in a ".php" file, add the following code in the place you want to show the number of online users and visitors:

4.To show the number of online visitors /users in a ".html" file, use this code:

<script type="text/javascript" src="usersontxt.php?uvon=showon"></script>

This script (and the other presented below) works with $_SESSION. At the beginning of the PHP file in which you use it, you must add: session_start();. Count Online users and visitors using a MySQL table

To register, count and show the number of online visitors and users in a MySQL table, require to perform three SQL queries: Delete the records older than a certain time. Insert a row with the new user /visitor, or, if it is already inserted, Update the timestamp in its column. Select the remaining rows. Here's the code for a script that uses a MySQL table (named "userson") to store and display the Online Users and Visitors.

  1. First we create the "userson" table, with 2 columns (uvon, dt). In the "uvon" column is stored the name of the user (if logged in) or the visitor's IP. In the "dt" column is stored a number with the timestamp (Unix time) when the page is accessed.
  • Add the following code in a php file (for example, named "create_userson.php"):

The code for create_userson.php:

header('Content-type: text/html; charset=utf-8');

// HERE add your data for connecting to MySQ database
$host = 'localhost';           // MySQL server address
$user = 'root';                // User name
$pass = 'password';            // User`s password
$dbname = 'database';          // Database name

// connect to the MySQL server
$conn = new mysqli($host, $user, $pass, $dbname);

// check connection
if (mysqli_connect_errno()) exit('Connect failed: '. mysqli_connect_error());

// sql query for CREATE "userson" TABLE
$sql = "CREATE TABLE `userson` (
 ) CHARACTER SET utf8 COLLATE utf8_general_ci"; 

// Performs the $sql query on the server to create the table
if ($conn->query($sql) === TRUE) echo 'Table "userson" successfully created';
else echo 'Error: '. $conn->error;

  1. Now we create the script that Inserts, Deletes, and Selects data in the userson table (For explanations about the code, see the comments in script).
  • Add the code below in another php file (named usersmysql.php): In both file you must add your personal data for connecting to MySQL database, in the variables: $host, $user, $pass, and $dbname .

The code for usersmysql.php:

// Script Online Users and Visitors -
if(!isset($_SESSION)) session_start();         // start Session, if not already started

// HERE add your data for connecting to MySQ database
$host = 'localhost';           // MySQL server address
$user = 'root';                // User name
$pass = 'password';            // User`s password
$dbname = 'database';          // Database name

 If you have an user registration script,
 replace $_SESSION['nume'] with the variable in which the user name is stored.
 You can get a free registration script from:

// get the user name if it is logged, or the visitors IP (and add the identifier)
$vst_id = '-vst-';         // an identifier to know that it is a visitor, not logged user
$uvon = isset($_SESSION['nume']) ? $_SESSION['nume'] : $_SERVER['SERVER_ADDR']. $vst_id;

$rgxvst = '/^([0-9\.]*)'. $vst_id. '/i';         // regexp to recognize the rows with visitors
$dt = time();                                    // current timestamp
$timeon = 120;             // number of secconds to keep a user online
$nrvst = 0;                                     // to store the number of visitors
$nrusr = 0;                                     // to store the number of usersrs
$usron = '';                                    // to store the name of logged users

// connect to the MySQL server
$conn = new mysqli($host, $user, $pass, $dbname);

// Define and execute the Delete, Insert/Update, and Select queries
$sqldel = "DELETE FROM `userson` WHERE `dt`<". ($dt - $timeon);
$sqliu = "INSERT INTO `userson` (`uvon`, `dt`) VALUES ('$uvon', $dt) ON DUPLICATE KEY UPDATE `dt`=$dt";
$sqlsel = "SELECT * FROM `userson`";

// Execute each query
if(!$conn->query($sqldel)) echo 'Error: '. $conn->error;
if(!$conn->query($sqliu)) echo 'Error: '. $conn->error;
$result = $conn->query($sqlsel);

// if the $result contains at least one row
if ($result->num_rows > 0) {
  // traverse the sets of results and set the number of online visitors and users ($nrvst, $nrusr)
  while($row = $result->fetch_assoc()) {
    if(preg_match($rgxvst, $row['uvon'])) $nrvst++;       // increment the visitors
    else {
      $nrusr++;                   // increment the users
      $usron .= '<br/> - <i>'.$row['uvon']. '</i>';          // stores the user's name

$conn->close();                  // close the MySQL connection

// the HTML code with data to be displayed
$reout = '<div id="uvon"><h4>Online: '. ($nrusr+$nrvst). '</h4>Visitors: '. $nrvst. '<br/>Users: '. $nrusr. $usron. '</div>';

// if access from <script>, with GET 'uvon=showon', adds the string to return into a JS statement
// in this way the script can also be included in .html files
if(isset($_GET['uvon']) && $_GET['uvon']=='showon') $reout = "document.write('$reout');";

echo $reout;             // output /display the result
  1. After you have created these two php files on your server, run the "create_userson.php" on your browser to create the "userson" table.

  2. Include the usersmysql.php file in the php file in which you want to display the number of online users and visitors.

  3. Or, if you want to insert it in a ".html" file, add this code:

Examples using these scripts

• Including the "usersontxt.php` in a php file:

<!doctype html>

Counter Online Users and Visitors

• Including the "usersmysql.php" in a html file:

<!doctype html>
 <meta charset="utf-8" />
 <title>Counter Online Users and Visitors</title>
 <meta name="description" content="PHP script to count and show the number of online users and visitors" />
 <meta name="keywords" content="online users, online visitors" />

<!-- Includes the script ("usersontxt.php", or "usersmysql.php") -->
<script type="text/javascript" src="usersmysql.php?uvon=showon"></script>


Both scripts (with storing data in a text file on the server, or into a MySQL table) will display a result like this: Online: 5

Visitors: 3 Users: 2

  • MarPlo
  • Marius

Python - OpenCV - imread - Displaying Image

In openCV whenever you try to display an oversized image or image bigger than your display resolution you get the cropped display. It's a default behaviour.
In order to view the image in the window of your choice openCV encourages to use named window. Please refer to namedWindow documentation

The function namedWindow creates a window that can be used as a placeholder for images and trackbars. Created windows are referred to by their names.

cv.namedWindow(name, flags=CV_WINDOW_AUTOSIZE) where each window is related to image container by the name arg, make sure to use same name


import cv2
frame = cv2.imread('1.jpg')
cv2.namedWindow("Display 1")
cv2.resizeWindow("Display 1", 300, 300)
cv2.imshow("Display 1", frame)

AngularJS - How can I do a redirect with a full page load?

Try this


XPath to select multiple tags

Not sure if this helps, but with XSL, I'd do something like:

<xsl:for-each select="a/b">
    <xsl:value-of select="c"/>
    <xsl:value-of select="d"/>
    <xsl:value-of select="e"/>

and won't this XPath select all children of B nodes:


Using $window or $location to Redirect in AngularJS

It seems that for full page reload $window.location.href is the preferred way.

It does not cause a full page reload when the browser URL is changed. To reload the page after changing the URL, use the lower-level API, $window.location.href.$location

Handling urllib2's timeout? - Python

In Python 2.7.3:

import urllib2
import socket

class MyException(Exception):

    urllib2.urlopen("", timeout = 1)
except urllib2.URLError as e:
    print type(e)    #not catch
except socket.timeout as e:
    print type(e)    #catched
    raise MyException("There was an error: %r" % e)

Python Pandas - Missing required dependencies ['numpy'] 1

I fixed this using Anaconda by going to Environments > base(root), searching for numpy in the installed modules and clicking the tickbox alongside it and choosing > Mark for specific version installation > 1.14.0 (as suggested by another user on this thread). Then clicking Apply. Once it downgraded numpy I stopped getting errors when running py files on the command line.

Throughout this saga, I was still able to use even when I was getting the numpy errors on the command line, but it was a hassle to create an exe every time I wanted to test a change. It's all sorted now. I guess there was a problem with numpy 1.16.4.

Anyway, I hope this helps someone who's using Anaconda as well.

Select Specific Columns from Spark DataFrame

Let's say our parent Dataframe has 'n' columns

we can create 'x' child DataFrames( Lets consider 2 in our case).

The columns for the child Dataframe can be chosen as per desire from any of the parent Dataframe columns.

Consider source has 10 columns and we want to split into 2 DataFrames that contains columns referenced from the parent Dataframe.

The columns for the child Dataframe can be decided using the select Dataframe API

val parentDF ="csv").load("/path of the CSV file")

val Child1_DF ="col1","col2","col3","col9","col10").show()

val child2_DF ="col5", "col6","col7","col8","col1","col2").show()

Notice that the column count in the child dataframes can differ in length and will be less than the parent dataframe column count.

we can also refer to the column names without mentioning the real names using the positional indexes of the desired column from the parent dataframe

Import spark implicits first which acts as a helper class for usage of $-notation to access the columns using the positional indexes

import spark.implicits._
import org.apache.spark.sql.functions._

val child3_DF  ="_c0","_c1","_c2","_c8","_c9").show()

we can also select column basing on certain conditions. Lets say we want only even numbered columns to be selected in the child dataframe. By even we refer to even indexed columns and index being starting from '0'

val parentColumns = parentDF.columns.toList

res0: List[String] = List(_c0, _c1, _c2, _c3, _c4, _c5, _c6, _c7,_c8,_c9)

val evenParentColumns =  res0.zipWithIndex.filter(_._2 % 2 == 0).map( _._1).toSeq

res1: scala.collection.immutable.Seq[String] = List(_c0, _c2, _c4, _c6,_c8)

Now feed these columns to be selected from the parentDF.Note that the select API need seq type arguments.So we converted the "evenParentColumns" to Seq collection

val child4_DF =, res1.tail:_*).show()

This will show the even indexed columns from the parent Dataframe.

| _c0 | _c2 | _c4 |_c6 |_c8 |

|ITE00100554|TMAX|null| E| 1 |

|TE00100554 |TMIN|null| E| 4 |

|GM000010962|PRCP|null| E| 7 |

So Now we are left with the even numbered columns in the dataframe

Similarly we can also apply other operations to the Dataframe column like shown below

val child5_DF =$"_c0", $"_c8" + 1).show()

So by many ways as mentioned we can select the columns in the Dataframe.

logger configuration to log to file and print to stdout

Adding a StreamHandler without arguments goes to stderr instead of stdout. If some other process has a dependency on the stdout dump (i.e. when writing an NRPE plugin), then make sure to specify stdout explicitly or you might run into some unexpected troubles.

Here's a quick example reusing the assumed values and LOGFILE from the question:

import logging
from logging.handlers import RotatingFileHandler
from logging import handlers
import sys

log = logging.getLogger('')
format = logging.Formatter("%(asctime)s - %(name)s - %(levelname)s - %(message)s")

ch = logging.StreamHandler(sys.stdout)

fh = handlers.RotatingFileHandler(LOGFILE, maxBytes=(1048576*5), backupCount=7)

Design Android EditText to show error message as described by google

There's no need to use a third-party library since Google introduced the TextInputLayout as part of the design-support-library.

Following a basic example:



        android:hint="Enter your name" />


Note: By setting app:errorEnabled="true" as an attribute of the TextInputLayout it won't change it's size once an error is displayed - so it basically blocks the space.


In order to show the Error below the EditText you simply need to call #setError on the TextInputLayout (NOT on the child EditText):

TextInputLayout til = (TextInputLayout) findViewById(;
til.setError("You need to enter a name");


picture showing the edit text with the error message

To hide the error and reset the tint simply call til.setError(null).


In order to use the TextInputLayout you have to add the following to your build.gradle dependencies:

dependencies {
    compile ''

Setting a custom color

By default the line of the EditText will be red. If you need to display a different color you can use the following code as soon as you call setError.

editText.getBackground().setColorFilter(getResources().getColor(R.color.red_500_primary), PorterDuff.Mode.SRC_ATOP);

To clear it simply call the clearColorFilter function, like this:


Is it possible in Java to access private fields via reflection

Yes it is possible.

You need to use the getDeclaredField method (instead of the getField method), with the name of your private field:

Field privateField = Test.class.getDeclaredField("str");

Additionally, you need to set this Field to be accessible, if you want to access a private field:


Once that's done, you can use the get method on the Field instance, to access the value of the str field.

TypeError: can't use a string pattern on a bytes-like object in re.findall()

The problem is that your regex is a string, but html is bytes:

>>> type(html)
<class 'bytes'>

Since python doesn't know how those bytes are encoded, it throws an exception when you try to use a string regex on them.

You can either decode the bytes to a string:

html = html.decode('ISO-8859-1')  # encoding may vary!
title = re.findall(pattern, html)  # no more error

Or use a bytes regex:

regex = rb'<title>(,+?)</title>'
#        ^

In this particular context, you can get the encoding from the response headers:

with urllib.request.urlopen(url) as response:
    encoding ='charset', 'utf8')
    html =

See the urlopen documentation for more details.

Using CSS in Laravel views?

For Laravel 5.4 and if you are using mix helper, use

    <link href="{{ mix('/css/app.css') }}" rel="stylesheet">
    <script src="{{ mix('/js/app.js') }}"></script>

Cancel a vanilla ECMAScript 6 Promise chain

I am still working through this idea, but here is how I have implemented a cancellable Promise using setTimeout as an example.

The idea is that a promise is resolved or rejected whenever you have decided it is, so it should be a matter of deciding when you want to cancel, satisfying the criterion, and then calling the reject() function yourself.

  • First, I think there are two reasons to finish a promise early: to get it over and done with (which I have called resolve) and to cancel (which I have called reject). Of course, that’s just my feeling. Of course there is a Promise.resolve() method, but it’s in the constructor itself, and returns a dummy resolved promise. This instance resolve() method actually resolves an instantiated promise object.

  • Second, you can happily add anything you like to a newly created promise object before you return it, and so I have just added resolve() and reject() methods to make it self-contained.

  • Third, the trick is to be able to access the executor resolve and reject functions later, so I have simply stored them in a simple object from within the closure.

I think the solution is simple, and I can’t see any major problems with it.

function wait(delay) {_x000D_
  var promise;_x000D_
  var timeOut;_x000D_
  var executor={};_x000D_
  promise=new Promise(function(resolve,reject) {_x000D_
    executor={resolve,reject};  //  Store the resolve and reject methods_x000D_
      console.log(`Timed Out`);_x000D_
  //  Implement your own resolve methods,_x000D_
  //  then access the stored methods_x000D_
      promise.reject=function() {_x000D_
      promise.resolve=function() {_x000D_
  return promise;_x000D_
var promise;_x000D_
  .then(()=>console.log('I have finished'))_x000D_
  .catch(()=>console.log('or not'));_x000D_
document.querySelector('button#cancel').onclick=()=>{ promise.reject(); }_x000D_
document.querySelector('button#finish').onclick=()=>{ promise.resolve(); }
<button id="start">Start</button>_x000D_
<button id="cancel">Cancel</button>_x000D_
<button id="finish">Finish</button>

Can I use multiple versions of jQuery on the same page?

Yes, it's doable due to jQuery's noconflict mode.

<!-- load jQuery 1.1.3 -->
<script type="text/javascript" src=""></script>
<script type="text/javascript">
var jQuery_1_1_3 = $.noConflict(true);

<!-- load jQuery 1.3.2 -->
<script type="text/javascript" src=""></script>
<script type="text/javascript">
var jQuery_1_3_2 = $.noConflict(true);

Then, instead of $('#selector').function();, you'd do jQuery_1_3_2('#selector').function(); or jQuery_1_1_3('#selector').function();.

How can I use/create dynamic template to compile dynamic Component with Angular 2.0?

In angular 7.x I used angular-elements for this.

  1. Install @angular-elements npm i @angular/elements -s

  2. Create accessory service.

import { Injectable, Injector } from '@angular/core';
import { createCustomElement } from '@angular/elements';
import { IStringAnyMap } from 'src/app/core/models';
import { AppUserIconComponent } from 'src/app/shared';

const COMPONENTS = {
  'user-icon': AppUserIconComponent

  providedIn: 'root'
export class DynamicComponentsService {
  constructor(private injector: Injector) {


  public register(): void {
    Object.entries(COMPONENTS).forEach(([key, component]: [string, any]) => {
      const CustomElement = createCustomElement(component, { injector: this.injector });
      customElements.define(key, CustomElement);

  public create(tagName: string, data: IStringAnyMap = {}): HTMLElement {
    const customEl = document.createElement(tagName);

    Object.entries(data).forEach(([key, value]: [string, any]) => {
      customEl[key] = value;

    return customEl;

Note that you custom element tag must be different with angular component selector. in AppUserIconComponent:

selector: app-user-icon

and in this case custom tag name I used "user-icon".

  1. Then you must call register in AppComponent:
  selector: 'app-root',
  template: '<router-outlet></router-outlet>'
export class AppComponent {
    dynamicComponents: DynamicComponentsService,
  ) {

  1. And now in any place of your code you can use it like this:
dynamicComponents.create('user-icon', {user:{...}});

or like this:

const html = `<div class="wrapper"><user-icon class="user-icon" user='${JSON.stringify(rec.user)}'></user-icon></div>`;

this.content = this.domSanitizer.bypassSecurityTrustHtml(html);

(in template):

<div class="comment-item d-flex" [innerHTML]="content"></div>

Note that in second case you must pass objects with JSON.stringify and after that parse it again. I can't find better solution.

When should I create a destructor?

Destructors provide an implicit way of freeing unmanaged resources encapsulated in your class, they get called when the GC gets around to it and they implicitly call the Finalize method of the base class. If you're using a lot of unmanaged resources it is better to provide an explicit way of freeing those resources via the IDisposable interface. See the C# programming guide:

converting list to json format - quick and easy way

I would avoid rolling your own and use either:



Both will do an excellent job :)

Add new column in Pandas DataFrame Python

You just do an opposite comparison. if Col2 <= 1. This will return a boolean Series with False values for those greater than 1 and True values for the other. If you convert it to an int64 dtype, True becomes 1 and False become 0,

df['Col3'] = (df['Col2'] <= 1).astype(int)

If you want a more general solution, where you can assign any number to Col3 depending on the value of Col2 you should do something like:

df['Col3'] = df['Col2'].map(lambda x: 42 if x > 1 else 55)


df['Col3'] = 0
condition = df['Col2'] > 1
df.loc[condition, 'Col3'] = 42
df.loc[~condition, 'Col3'] = 55

Convert regular Python string to raw string

For Python 3, the way to do this that doesn't add double backslashes and simply preserves \n, \t, etc. is:

a = 'hello\nbobby\nsally\n'
a.encode('unicode-escape').decode().replace('\\\\', '\\')

Which gives a value that can be written as CSV:


There doesn't seem to be a solution for other special characters, however, that may get a single \ before them. It's a bummer. Solving that would be complex.

For example, to serialize a pandas.Series containing a list of strings with special characters in to a textfile in the format BERT expects with a CR between each sentence and a blank line between each document:

with open('sentences.csv', 'w') as f:

    current_idx = 0
    for idx, doc in sentences.items():
        # Insert a newline to separate documents
        if idx != current_idx:
        # Write each sentence exactly as it appared to one line each
        for sentence in doc:
            f.write(sentence.encode('unicode-escape').decode().replace('\\\\', '\\') + '\n')

This outputs (for the Github CodeSearchNet docstrings for all languages tokenized into sentences):

Makes sure the fast-path emits in order.
@param value the value to emit or queue up\n@param delayError if true, errors are delayed until the source has terminated\n@param disposable the resource to dispose if the drain terminates

Mirrors the one ObservableSource in an Iterable of several ObservableSources that first either emits an item or sends\na termination notification.
Scheduler:\n{@code amb} does not operate by default on a particular {@link Scheduler}.
@param  the common element type\n@param sources\nan Iterable of ObservableSource sources competing to react first.
A subscription to each source will\noccur in the same order as in the Iterable.
@return an Observable that emits the same sequence as whichever of the source ObservableSources first\nemitted an item or sent a termination notification\n@see ReactiveX operators documentation: Amb


How do you set the Content-Type header for an HttpClient request?

.Net tries to force you to obey certain standards, namely that the Content-Type header can only be specified on requests that have content (e.g. POST, PUT, etc.). Therefore, as others have indicated, the preferred way to set the Content-Type header is through the HttpContent.Headers.ContentType property.

With that said, certain APIs (such as the LiquidFiles Api, as of 2016-12-19) requires setting the Content-Type header for a GET request. .Net will not allow setting this header on the request itself -- even using TryAddWithoutValidation. Furthermore, you cannot specify a Content for the request -- even if it is of zero-length. The only way I could seem to get around this was to resort to reflection. The code (in case some else needs it) is

var field = typeof(System.Net.Http.Headers.HttpRequestHeaders)
    .GetField("invalidHeaders", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static) 
  ?? typeof(System.Net.Http.Headers.HttpRequestHeaders) 
    .GetField("s_invalidHeaders", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);
if (field != null)
  var invalidFields = (HashSet<string>)field.GetValue(null);
_client.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", "text/xml");


As noted in the comments, this field has different names in different versions of the dll. In the source code on GitHub, the field is currently named s_invalidHeaders. The example has been modified to account for this per the suggestion of @David Thompson.

AND/OR in Python?

Are you looking for...

a if b else c

Or perhaps you misunderstand Python's or? True or True is True.

How to add bootstrap to an angular-cli project

2 simple steps

  1. Install Bootstrap ( am installing latest version)

npm install bootstrap@next
  1. Import into your project, add below line in your styles.scss

@import '~bootstrap';

Please Note your order of imports might matter, if you have other libraries which uses bootstrap, please keep this import statement on top

The End. :)

NOTE: below are my versions

angular : 9

node : v10.16.0

npm : 6.9.1

How to query a CLOB column in Oracle

To add to the answer.

v_result clob;
---- some operation on v_result
dbms_lob.substr( v_result, 4000 ,length(v_result) - 3999 );


In dbms_lob.substr

first parameter is clob which you want to extract .

Second parameter is how much length of clob you want to extract.

Third parameter is from which word you want to extract .

In above example i know my clob size is more than 50000 , so i want last 4000 character .

What is the difference between putting a property on application.yml or bootstrap.yml in spring boot?

Bootstrap.yml is the first file loaded when you start spring boot application and is loaded when application starts. So, you keep, may be your config server's credentials etc., in bootstrap.yml which is required during loading application and then in you keep may be database URL etc.

How to do relative imports in Python?
app/ ->
    package_a/ ->
    package_b/ ->
  1. You run python
  2. does: import app.package_a.module_a
  3. does import app.package_b.module_b

Alternatively 2 or 3 could use: from app.package_a import module_a

That will work as long as you have app in your PYTHONPATH. could be anywhere then.

So you write a to copy (install) the whole app package and subpackages to the target system's python folders, and to target system's script folders.

Calculating time difference in Milliseconds

I pretty much like the (relatively) new java.time library: it's close to awesome, imho.

You can calculate a duration between two instants this way:

import java.time.*

Instant before =;
// do stuff
Instant after =;
long delta = Duration.between(before, after).toMillis(); // .toWhatsoever()

API is awesome, highly readable and intuitive.

Classes are thread-safe too. !

References: Oracle Tutorial, Java Magazine

How to determine an object's class?

checking with isinstance() would not be enough if you want to know in run time. use:

    // do something

Simple export and import of a SQLite database on Android

This is a simple method to export the database to a folder named backup folder you can name it as you want and a simple method to import the database from the same folder a

    public class ExportImportDB extends Activity {
        protected void onCreate(Bundle savedInstanceState) {
            // TODO Auto-generated method stub
//creating a new folder for the database to be backuped to
            File direct = new File(Environment.getExternalStorageDirectory() + "/Exam Creator");

                       //directory is created;


    //importing database
        private void importDB() {
            // TODO Auto-generated method stub

            try {
                File sd = Environment.getExternalStorageDirectory();
                File data  = Environment.getDataDirectory();

                if (sd.canWrite()) {
                    String  currentDBPath= "//data//" + "PackageName"
                            + "//databases//" + "DatabaseName";
                    String backupDBPath  = "/BackupFolder/DatabaseName";
                    File  backupDB= new File(data, currentDBPath);
                    File currentDB  = new File(sd, backupDBPath);

                    FileChannel src = new FileInputStream(currentDB).getChannel();
                    FileChannel dst = new FileOutputStream(backupDB).getChannel();
                    dst.transferFrom(src, 0, src.size());
                    Toast.makeText(getBaseContext(), backupDB.toString(),

            } catch (Exception e) {

                Toast.makeText(getBaseContext(), e.toString(), Toast.LENGTH_LONG)

    //exporting database 
        private void exportDB() {
            // TODO Auto-generated method stub

            try {
                File sd = Environment.getExternalStorageDirectory();
                File data = Environment.getDataDirectory();

                if (sd.canWrite()) {
                    String  currentDBPath= "//data//" + "PackageName"
                            + "//databases//" + "DatabaseName";
                    String backupDBPath  = "/BackupFolder/DatabaseName";
                    File currentDB = new File(data, currentDBPath);
                    File backupDB = new File(sd, backupDBPath);

                    FileChannel src = new FileInputStream(currentDB).getChannel();
                    FileChannel dst = new FileOutputStream(backupDB).getChannel();
                    dst.transferFrom(src, 0, src.size());
                    Toast.makeText(getBaseContext(), backupDB.toString(),

            } catch (Exception e) {

                Toast.makeText(getBaseContext(), e.toString(), Toast.LENGTH_LONG)



Dont forget to add this permission to proceed it

  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" >


How to access the correct `this` inside a callback?

Here are several ways to access parent context inside child context -

  1. You can use bind() function.
  2. Store reference to context/this inside another variable(see below example).
  3. Use ES6 Arrow functions.
  4. Alter code/function design/architecture - for this you should have command over design patterns in javascript.

1. Use bind() function

function MyConstructor(data, transport) { = data;
    transport.on('data', ( function () {
    }).bind(this) );
// Mock transport object
var transport = {
    on: function(event, callback) {
        setTimeout(callback, 1000);
// called as
var obj = new MyConstructor('foo', transport);

If you are using underscore.js -

transport.on('data', _.bind(function () {
}, this));

2 Store reference to context/this inside another variable

function MyConstructor(data, transport) {
  var self = this; = data;
  transport.on('data', function() {

3 Arrow function

function MyConstructor(data, transport) { = data;
  transport.on('data', () => {

How to set lifetime of session

The sessions on PHP works with a Cookie type session, while on server-side the session information is constantly deleted.

For set the time life in php, you can use the function session_set_cookie_params, before the session_start:


For ex, 3600 seconds is one hour, for 2 hours 3600*2 = 7200.

But it is session cookie, the browser can expire it by itself, if you want to save large time sessions (like remember login), you need to save the data in the server and a standard cookie in the client side.

You can have a Table "Sessions":

  • session_id int
  • session_hash varchar(20)
  • session_data text

And validating a Cookie, you save the "session id" and the "hash" (for security) on client side, and you can save the session's data on the server side, ex:

On login:

setcookie('sessid', $sessionid, 604800);      // One week or seven days
setcookie('sesshash', $sessionhash, 604800);  // One week or seven days
// And save the session data:
saveSessionData($sessionid, $sessionhash, serialize($_SESSION)); // saveSessionData is your function

If the user return:

if (isset($_COOKIE['sessid'])) {
    if (valide_session($_COOKIE['sessid'], $_COOKIE['sesshash'])) {
        $_SESSION = unserialize(get_session_data($_COOKIE['sessid']));
    } else {
        // Dont validate the hash, possible session falsification

Obviously, save all session/cookies calls, before sending data.

How do I remove the last comma from a string using PHP?

Try the below code:

$my_string = "'name', 'name2', 'name3',";
echo substr(trim($my_string), 0, -1);

Use this code to remove the last character of the string.

How to get a date in YYYY-MM-DD format from a TSQL datetime field?

Seems unnecessary to do any strange things, if you want your date to be seperated by slash. Just escape it with a backslash. Otherwise you will end up with a dot.


Tested on SQL Server 2016

How to change legend size with matplotlib.pyplot

This should do

import pylab as plot
params = {'legend.fontsize': 20,
          'legend.handlelength': 2}

Then do the plot afterwards.

There are a ton of other rcParams, they can also be set in the matplotlibrc file.

Also presumably you can change it passing a matplotlib.font_manager.FontProperties instance but this I don't know how to do. --> see Yann's answer.

Nginx 403 forbidden for all files

If you still see permission denied after verifying the permissions of the parent folders, it may be SELinux restricting access.

To check if SELinux is running:

# getenforce

To disable SELinux until next reboot:

# setenforce Permissive

Restart Nginx and see if the problem persists. To allow nginx to serve your www directory (make sure you turn SELinux back on before testing this. i.e, setenforce Enforcing)

# chcon -Rt httpd_sys_content_t /path/to/www

See my answer here for more details

How to change css property using javascript

Just for the info, this can be done with CSS only with just minor HTML and CSS changes


<div class="left">
<div class="right">
<div class="center">
       <div class="left1">
       <div class="right1">


.left, .right{
    border:1px solid red;
.left:hover, .right:hover{
    border:1px solid blue;
     float :right;

.center .left1, .center .right1{
    border:1px solid green;
.left:hover ~ .center .left1 {

.right:hover ~ .center .right1 {

and the DEMO:

What is the purpose of XSD files?

XSDs constrain the vocabulary and structure of XML documents.

  • Without an XSD, an XML document need only follow the rules for being well-formed as given in the W3C XML Recommendation.
  • With an XSD, an XML document must adhere to additional constraints placed upon the names and values of its elements and attributes in order to be considered valid against the XSD per the W3C XML Schema Recommendation.

XML is all about agreement, and XSDs provide the means for structuring and communicating the agreement beyond the basic definition of XML itself.

I'm getting Key error in python

I received this error when I was parsing dict with nested for:

cats = {'Tom': {'color': 'white', 'weight': 8}, 'Klakier': {'color': 'black', 'weight': 10}}
cat_attr = {}
for cat in cats:
    for attr in cat:


Traceback (most recent call last):
      File "<input>", line 3, in <module>
    KeyError: 'K'

Because in second loop should be cats[cat] instead just cat (what is just a key)


cats = {'Tom': {'color': 'white', 'weight': 8}, 'Klakier': {'color': 'black', 'weight': 10}}
cat_attr = {}
for cat in cats:
    for attr in cats[cat]:



Anaconda site-packages

I installed miniconda and found all the installed packages in /miniconda3/pkgs

Please explain about insertable=false and updatable=false in reference to the JPA @Column annotation

An other example would be on the "created_on" column where you want to let the database handle the date creation

How to subtract/add days from/to a date?

There is of course a lubridate solution for this:

date <- "2009-10-01"

ymd(date) - 5
# [1] "2009-09-26"

is the same as

ymd(date) - days(5)
# [1] "2009-09-26"

Other time formats could be:

ymd(date) - months(5)
# [1] "2009-05-01"

ymd(date) - years(5)
# [1] "2004-10-01"

ymd(date) - years(1) - months(2) - days(3)
# [1] "2008-07-29"

AngularJS - Attribute directive input value change

There's a great example in the AngularJS docs.

It's very well commented and should get you pointed in the right direction.

A simple example, maybe more so what you're looking for is below:



<div ng-app="myDirective" ng-controller="x">
    <input type="text" ng-model="test" my-directive>


angular.module('myDirective', [])
    .directive('myDirective', function () {
    return {
        restrict: 'A',
        link: function (scope, element, attrs) {
            scope.$watch(attrs.ngModel, function (v) {
                console.log('value changed, new value is: ' + v);

function x($scope) {
    $scope.test = 'value here';

Edit: Same thing, doesn't require ngModel jsfiddle:


angular.module('myDirective', [])
    .directive('myDirective', function () {
    return {
        restrict: 'A',
        scope: {
            myDirective: '='
        link: function (scope, element, attrs) {
            // set the initial value of the textbox
  'old-value', scope.myDirective);

            // detect outside changes and update our input
            scope.$watch('myDirective', function (val) {

            // on blur, update the value in scope
            element.bind('propertychange keyup paste', function (blurEvent) {
                if ('old-value') != element.val()) {
                    console.log('value changed, new value is: ' + element.val());
                    scope.$apply(function () {
                        scope.myDirective = element.val();
              'old-value', element.val());

function x($scope) {
    $scope.test = 'value here';

can't access mysql from command line mac

Just do the following in your terminal:

echo $PATH

If your given path is not in that string, you have to add it like this: export PATH=$PATH:/usr/local/ or export PATH=$PATH:/usr/local/mysql/bin

Monad in plain English? (For the OOP programmer with no FP background)

From a practical point of view (summarizing what has been said in many previous answers and related articles), it seems to me that one of the fundamental "purposes" (or usefulness) of the monad is to leverage the dependencies implicit in recursive method invocations aka function composition (i.e. when f1 calls f2 calls f3, f3 needs to be evaluated before f2 before f1) to represent sequential composition in a natural way, especially in the context of a lazy evaluation model (that is, sequential composition as a plain sequence, e.g. "f3(); f2(); f1();" in C - the trick is especially obvious if you think of a case where f3, f2 and f1 actually return nothing [their chaining as f1(f2(f3)) is artificial, purely intended to create sequence]).

This is especially relevant when side-effects are involved, i.e. when some state is altered (if f1, f2, f3 had no side-effects, it wouldn't matter in what order they're evaluated; which is a great property of pure functional languages, to be able to parallelize those computations for example). The more pure functions, the better.

I think from that narrow point of view, monads could be seen as syntactic sugar for languages that favor lazy evaluation (that evaluate things only when absolutely necessary, following an order that does not rely on the presentation of the code), and that have no other means of representing sequential composition. The net result is that sections of code that are "impure" (i.e. that do have side-effects) can be presented naturally, in an imperative manner, yet are cleanly separated from pure functions (with no side-effects), which can be evaluated lazily.

This is only one aspect though, as warned here.

The model backing the 'ApplicationDbContext' context has changed since the database was created

I know I am very late, but I want to give contribution too. This error is really strange, because the browser is not able to understand how the changes should be rendered because the classes and their properties might have changed but not committed to the database.

So do one thing,

create one migration in Package Manager Console(Tools > NuGet Package Manager > Package Manager Console) using this command:

add-migration UpdateMigration

where UpdateMigration is the name of your Migration. You can give it any name of your choice but please be specific.

After that, we just need to update the database, so run this:


Now that you have committed your changes to the database, just refresh your browser and there you go!

Hope this helps.

Convert a positive number to negative in C#

X=*-1 may not work on all compilers... since it reads a 'multiply' 'SUBTRACT' 1 instead of NEGATIVE The better alt is X=(0-X), [WHICH IS DIFF FROM X-=X]

Lightweight workflow engine for Java

CamundaBPM is one option. You can check here:

Laravel Checking If a Record Exists

In your Controller

$this->validate($request, [
        'email' => 'required|unique:user|email',

In your View - Display Already Exist Message

@if (count($errors) > 0)
    <div class="alert alert-danger">
            @foreach ($errors->all() as $error)
                <li>{{ $error }}</li>

Match line break with regular expression

You could search for:

<li><a href="#">[^\n]+

And replace with:


Where $0 is the whole match. The exact semantics will depend on the language are you using though.

WARNING: You should avoid parsing HTML with regex. Here's why.

Change font-weight of FontAwesome icons?

Webkit browsers support the ability to add "stroke" to fonts. This bit of style makes fonts look thinner (assuming a white background):

-webkit-text-stroke: 2px white;

Example on codepen here: Some people are using SVG for a cross-platform "stroke" solution:

T-sql - determine if value is integer

When (LNSEQNBR / 16384)%1 = 0 then 1 else 0 end

How to force a html5 form validation without submitting it via jQuery

    if $("form")[0].checkValidity()
        url: "url"
        type: "post"
        data: {

        dataType: "json"
        success: (data) ->


from: html5 form validation

Detect end of ScrollView

To determine if you are at the end of your custom ScrollView you could also use a member variable and store the last y-position. Then you can compare the last y-position with the current scroll position.

private int scrollViewPos;


public void onScrollChanged(ScrollViewExt scrollView, int x, int y, int oldx, int oldy) {

   //reached end of scrollview
   if (y > 0 && scrollViewPos == y){
      //do something

   scrollViewPos = y;

E11000 duplicate key error index in mongodb mongoose

I had a similar problem and I realized that by default mongo only supports one schema per collection. Either store your new schema in a different collection or delete the existing documents with the incompatible schema within the your current collection. Or find a way to have more than one schema per collection.

How to handle AssertionError in Python and find out which line or statement it occurred on?

The traceback module and sys.exc_info are overkill for tracking down the source of an exception. That's all in the default traceback. So instead of calling exit(1) just re-raise:

    assert "birthday cake" == "ice cream cake", "Should've asked for pie"
except AssertionError:
    print 'Houston, we have a problem.'

Which gives the following output that includes the offending statement and line number:

Houston, we have a problem.
Traceback (most recent call last):
  File "/tmp/", line 2, in <module>
    assert "birthday cake" == "ice cream cake", "Should've asked for pie"
AssertionError: Should've asked for pie

Similarly the logging module makes it easy to log a traceback for any exception (including those which are caught and never re-raised):

import logging

    assert False == True 
except AssertionError:
    logging.error("Nothing is real but I can't quit...", exc_info=True)

'git status' shows changed files, but 'git diff' doesn't

As already noted in a previous answer, this situation may arise due to line-ending problems (CR/LF vs. LF). I solved this problem (under Git version 2.22.0) with this command:

git add --renormalize .

According to the manual:

           Apply the "clean" process freshly to all tracked files to
           forcibly add them again to the index. This is useful after
           changing core.autocrlf configuration or the text attribute in
           order to correct files added with wrong CRLF/LF line endings.
           This option implies -u.

How to check String in response body with mockMvc

Another option is:


def response = mockMvc.perform(
            .header("Content-Type", "application/json"))


response.andReturn().getResponse().getContentAsString() == "what you expect"

Mercurial: how to amend the last commit?

I'm tuning into what krtek has written. More specifically solution 1:


  • you've committed one (!) changeset but have not pushed it yet
  • you want to modify this changeset (e.g. add, remove or change files and/or the commit message)


  • use hg rollback to undo the last commit
  • commit again with the new changes in place

The rollback really undoes the last operation. Its way of working is quite simple: normal operations in HG will only append to files; this includes a commit. Mercurial keeps track of the file lengths of the last transaction and can therefore completely undo one step by truncating the files back to their old lengths.

How do I return a char array from a function?

Best as an out parameter:

void testfunc(char* outStr){
  char str[10];
  for(int i=0; i < 10; ++i){
    outStr[i] = str[i];

Called with

int main(){
  char myStr[10];
  // myStr is now filled

TypeScript, Looping through a dictionary

< ES 2017:

Object.keys(obj).forEach(key => {
  let value = obj[key];

>= ES 2017:

  ([key, value]) => console.log(key, value)

what is the use of Eval() in

Eval is used to bind to an UI item that is setup to be read-only (eg: a label or a read-only text box), i.e., Eval is used for one way binding - for reading from a database into a UI field.

It is generally used for late-bound data (not known from start) and usually bound to the smallest part of the data-bound control that contains a whole record. The Eval method takes the name of a data field and returns a string containing the value of that field from the current record in the data source. You can supply an optional second parameter to specify a format for the returned string. The string format parameter uses the syntax defined for the Format method of the String class.

How do you run a single test/spec file in RSpec?

You can also use the actual text of the *e*xample test case with -e !

So for:

it "shows the plane arrival time"

you can use

rspec path/to/spec/file.rb -e 'shows the plane arrival time'
./scripts/spec path/to/spec/file.rb -e 'shows the plane arrival time'

no need for rake here.

How to achieve pagination/table layout with Angular.js?

The simplest way is using slice. You pipe the slice and mention the start index and end index for the part of the data you wish to display. Here is the code:

     <tr *ngFor="let row of rowData | slice:startIndex:endIndex">
<nav *ngIf="rowData" aria-label="Page navigation example">
    <ul class="pagination">
        <li class="page-item">
            <a class="page-link" (click)="updateIndex(0)" aria-label="Previous">
                <span aria-hidden="true">First</span>
        <li *ngFor="let i of getArrayFromNumber(rowData.length)" class="page-item">
            <a class="page-link" (click)="updateIndex(i)">{{i+1}}</a></li>

        <li class="page-item">
            <a class="page-link" (click)="updateIndex(pageNumberArray.length-1)" aria-label="Next">
                <span aria-hidden="true">Last</span>


public rowData = data // data you want to display in table
public paginationRowCount = 100 //number of records in a page
getArrayFromNumber(length) {
        if (length % this.paginationRowCount === 0) {
            this.pageNumberArray = Array.from(Array(Math.floor(length / this.paginationRowCount)).keys());
        } else {
            this.pageNumberArray = Array.from(Array(Math.floor(length / this.paginationRowCount) + 1).keys());
        return this.pageNumberArray;

    updateIndex(pageIndex) {
        this.startIndex = pageIndex * this.paginationRowCount;
        if (this.rowData.length > this.startIndex + this.paginationRowCount) {
            this.endIndex = this.startIndex + this.paginationRowCount;
        } else {
            this.endIndex = this.rowData.length;

Refence for tutorial:

Last executed queries for a specific database

This works for me to find queries on any database in the instance. I'm sysadmin on the instance (check your privileges):

SELECT deqs.last_execution_time AS [Time], dest.text AS [Query], dest.*
FROM sys.dm_exec_query_stats AS deqs
CROSS APPLY sys.dm_exec_sql_text(deqs.sql_handle) AS dest
WHERE dest.dbid = DB_ID('msdb')
ORDER BY deqs.last_execution_time DESC

This is the same answer that Aaron Bertrand provided but it wasn't placed in an answer.

Array to Hash Ruby

Or if you have an array of [key, value] arrays, you can do:

[[1, 2], [3, 4]].inject({}) do |r, s|
  r.merge!({s[0] => s[1]})
end # => { 1 => 2, 3 => 4 }

Password masking console application

I found a bug in shermy's vanilla C# 3.5 .NET solution which otherwise works a charm. I have also incorporated Damian Leszczynski - Vash's SecureString idea here but you can use an ordinary string if you prefer.

THE BUG: If you press backspace during the password prompt and the current length of the password is 0 then an asterisk is incorrectly inserted in the password mask. To fix this bug modify the following method.

    public static string ReadPassword(char mask)
        const int ENTER = 13, BACKSP = 8, CTRLBACKSP = 127;
        int[] FILTERED = { 0, 27, 9, 10 /*, 32 space, if you care */ }; // const

        SecureString securePass = new SecureString();

        char chr = (char)0;

        while ((chr = System.Console.ReadKey(true).KeyChar) != ENTER)
            if (((chr == BACKSP) || (chr == CTRLBACKSP)) 
                && (securePass.Length > 0))
                System.Console.Write("\b \b");
                securePass.RemoveAt(securePass.Length - 1);

            // Don't append * when length is 0 and backspace is selected
            else if (((chr == BACKSP) || (chr == CTRLBACKSP)) && (securePass.Length == 0))

            // Don't append when a filtered char is detected
            else if (FILTERED.Count(x => chr == x) > 0)

            // Append and write * mask

        IntPtr ptr = new IntPtr();
        ptr = Marshal.SecureStringToBSTR(securePass);
        string plainPass = Marshal.PtrToStringBSTR(ptr);
        return plainPass;

Execution sequence of Group By, Having and Where clause in SQL Server?

Think about what you need to do if you wish to implement:

  • WHERE: Its need to execute the JOIN operations.
  • GROUP BY: You specify Group by to "group" the results on the join, then it has to after the JOIN operation, after the WHERE usage.
  • HAVING: HAVING is for filtering as GROUP BY expressions says. Then, it is executed after the GROUP BY.

The order is WHERE, GROUP BY and HAVING.

Creating an empty file in C#

A somewhat common use case for creating an empty file is to trigger something else happening in a different process in the absence of more sophisticated in process communication. In this case, it can help to have the file creation be atomic from the outside world's point of view (particularly if the thing being triggered is going to delete the file to "consume" the trigger).

So it can help to create a junk name (Guid.NewGuid.ToString()) in the same directory as the file you want to create, and then do a File.Move from the temporary name to your desired name. Otherwise triggered code which checks for file existence and then deletes the trigger may run into race conditions where the file is deleted before it is fully closed out.

Having the temp file in the same directory (and file system) gives you the atomicity you may want. This gives something like.

public void CreateEmptyFile(string path)
    string tempFilePath = Path.Combine(Path.GetDirectoryName(path),
    using (File.Create(tempFilePath)) {}
    File.Move(tempFilePath, path);

Multiple scenarios @RequestMapping produces JSON/XML together with Accept or ResponseEntity

All your problems are that you are mixing content type negotiation with parameter passing. They are things at different levels. More specific, for your question 2, you constructed the response header with the media type your want to return. The actual content negotiation is based on the accept media type in your request header, not response header. At the point the execution reaches the implementation of the method getPersonFormat, I am not sure whether the content negotiation has been done or not. Depends on the implementation. If not and you want to make the thing work, you can overwrite the request header accept type with what you want to return.

return new ResponseEntity<>(PersonFactory.createPerson(), httpHeaders, HttpStatus.OK);

Reading file line by line (with space) in Unix Shell scripting - Issue

You want to read raw lines to avoid problems with backslashes in the input (use -r):

while read -r line; do
   printf "<%s>\n" "$line"
done < file.txt

This will keep whitespace within the line, but removes leading and trailing whitespace. To keep those as well, set the IFS empty, as in

while IFS= read -r line; do
   printf "%s\n" "$line"
done < file.txt

This now is an equivalent of cat < file.txt as long as file.txt ends with a newline.

Note that you must double quote "$line" in order to keep word splitting from splitting the line into separate words--thus losing multiple whitespace sequences.

document.getElementById().value doesn't set the value

Refer below Code Snip

In HTML Page

<input id="test" type="number" value="0"/>

In Java Script

document.getElementById("test").value=request.responseText;// in case of String 
document.getElementById("test").value=new Number(responseText);// in case of Number

Exit Shell Script Based on Process Exit Code

  1. How do I get the exit code of cmd1 in cmd1|cmd2

    First, note that cmd1 exit code could be non-zero and still don't mean an error. This happens for instance in

    cmd | head -1

    You might observe a 141 (or 269 with ksh93) exit status of cmd1, but it's because cmd was interrupted by a SIGPIPE signal when head -1 terminated after having read one line.

    To know the exit status of the elements of a pipeline cmd1 | cmd2 | cmd3

    a. with Z shell (zsh):

    The exit codes are provided in the pipestatus special array. cmd1 exit code is in $pipestatus[1], cmd3 exit code in $pipestatus[3], so that $? is always the same as $pipestatus[-1].

    b. with Bash:

    The exit codes are provided in the PIPESTATUS special array. cmd1 exit code is in ${PIPESTATUS[0]}, cmd3 exit code in ${PIPESTATUS[2]}, so that $? is always the same as ${PIPESTATUS: -1}.


    For more details see Z shell.

Evenly distributing n points on a sphere

# create uniform spiral grid
numOfPoints = varargin[0]
vxyz = zeros((numOfPoints,3),dtype=float)
sq0 = 0.00033333333**2
sq2 = 0.9999998**2
sumsq = 2*sq0 + sq2
vxyz[numOfPoints -1] = array([(sqrt(sq0/sumsq)), 
vxyz[0] = -vxyz[numOfPoints -1] 
phi2 = sqrt(5)*0.5 + 2.5
rootCnt = sqrt(numOfPoints)
prevLongitude = 0
for index in arange(1, (numOfPoints -1), 1, dtype=float):
  zInc = (2*index)/(numOfPoints) -1
  radius = sqrt(1-zInc**2)

  longitude = phi2/(rootCnt*radius)
  longitude = longitude + prevLongitude
  while (longitude > 2*pi): 
    longitude = longitude - 2*pi

  prevLongitude = longitude
  if (longitude > pi):
    longitude = longitude - 2*pi

  latitude = arccos(zInc) - pi/2
  vxyz[index] = array([ (cos(latitude) * cos(longitude)) ,
                        (cos(latitude) * sin(longitude)), 

DBNull if statement

At first use ExecuteScalar

 objConn = new SqlConnection(strConnection);
 objCmd = new SqlCommand(strSQL, objConn);
 object result = cmd.ExecuteScalar();
 if(result == null)
     strLevel = "";
     strLevel = result.ToString();

Using for loop inside of a JSP

Do this

    <% for(int i = 0; i < allFestivals.size(); i+=1) { %>
    <% } %>

Better way is to use c:foreach see link jstl for each

Run a controller function whenever a view is opened/shown

Considering Ionic's ability to cache view elements and scope data mentioned above, this might be another way of doing, if you want to run the controller every time the view gets loaded. You can globally disable the caching mechanism used by ionic by doing:


Else, the way I had it working for me was doing

$scope.$on("$ionicView.afterLeave", function () {

This is to clear the cache before leaving the view to re-run controller every time you enter back again.

Android: ScrollView vs NestedScrollView

Other than the advantages listed in the answers given, one more advantage of NestedScrollView over ScrollView is its compatibility with CoordinatorLayout. The ScrollView does not cooperate with the CoordinatorLayout. You have to use NestedScrollView to get "scroll off-screen" behaviour for the toolbar.

Toolbar will not collapse with Scrollview as child of CoordinatorLayout

How do you create a toggle button?

You can just use toggleClass() to track state. Then you check if button element has the class, like this:

$("button.toggler").click( function() {
    $me = $(this);
    }else {

And I use the button element for buttons for semantic reasons.

<button class="toggler">Toggle me</button>

How do I delete unpushed git commits?

Do a git rebase -i FAR_ENOUGH_BACK and drop the line for the commit you don't want.

Creating a byte array from a stream

You can simply use ToArray() method of MemoryStream class, for ex-

MemoryStream ms = (MemoryStream)dataInStream;
byte[] imageBytes = ms.ToArray();

HTTP Error 503, the service is unavailable

Check your application's respective Application Framework Pool - it could be stopped. If it is, start it and check again.

If you're still experiencing issues you can also check out Event Viewer to find the cause of that error in order to troubleshoot more.

Generate Row Serial Numbers in SQL Query

I'm not certain, based on your question if you want numbered rows that will remember their numbers even if the underlying data changes (and gives a different ordering), but if you just want numbered rows - that reset on a change in customer ID, then try using the Partition by clause of row_number()

row_number() over(partition by CustomerID order by CustomerID)

Python error message io.UnsupportedOperation: not readable

Use a+ to open a file for reading, writing as well as create it if it doesn't exist.

a+ Opens a file for both appending and reading. The file pointer is at the end of the file if the file exists. The file opens in the append mode. If the file does not exist, it creates a new file for reading and writing. -Python file modes

with open('"File.txt', 'a+') as file:

Note: opening file in a with block makes sure that the file is properly closed at the block's end, even if an exception is raised on the way. It's equivalent to try-finally, but much shorter.

What is the difference between const and readonly in C#?

A const is a compile-time constant whereas readonly allows a value to be calculated at run-time and set in the constructor or field initializer. So, a 'const' is always constant but 'readonly' is read-only once it is assigned.

Eric Lippert of the C# team has more information on different types of immutability.

Can't start Eclipse - Java was started but returned exit code=13

Make sure you don't have special characters (%, $, #, etc.) at Eclipse path.

How to implement the factory method pattern in C++ correctly

This is my c++11 style solution. parameter 'base' is for base class of all sub-classes. creators, are std::function objects to create sub-class instances, might be a binding to your sub-class' static member function 'create(some args)'. This maybe not perfect but works for me. And it is kinda 'general' solution.

template <class base, class... params> class factory {
  factory() {}
  factory(const factory &) = delete;
  factory &operator=(const factory &) = delete;

  auto create(const std::string name, params... args) {
    auto key = your_hash_func(name.c_str(), name.size());
    return std::move(create(key, args...));

  auto create(key_t key, params... args) {
    std::unique_ptr<base> obj{creators_[key](args...)};
    return obj;

  void register_creator(const std::string name,
                        std::function<base *(params...)> &&creator) {
    auto key = your_hash_func(name.c_str(), name.size());
    creators_[key] = std::move(creator);

  std::unordered_map<key_t, std::function<base *(params...)>> creators_;

An example on usage.

class base {
  base(int val) : val_(val) {}

  virtual ~base() { std::cout << "base destroyed\n"; }

  int val_ = 0;

class foo : public base {
  foo(int val) : base(val) { std::cout << "foo " << val << " \n"; }

  static foo *create(int val) { return new foo(val); }

  virtual ~foo() { std::cout << "foo destroyed\n"; }

class bar : public base {
  bar(int val) : base(val) { std::cout << "bar " << val << "\n"; }

  static bar *create(int val) { return new bar(val); }

  virtual ~bar() { std::cout << "bar destroyed\n"; }

int main() {
  common::factory<base, int> factory;

  auto foo_creator = std::bind(&foo::create, std::placeholders::_1);
  auto bar_creator = std::bind(&bar::create, std::placeholders::_1);

  factory.register_creator("foo", foo_creator);
  factory.register_creator("bar", bar_creator);

    auto foo_obj = std::move(factory.create("foo", 80));

    auto bar_obj = std::move(factory.create("bar", 90));

How do you get the process ID of a program in Unix or Linux using Python?

With psutil:

(can be installed with [sudo] pip install psutil)

import psutil

# Get current process pid
current_process_pid = psutil.Process().pid
print(current_process_pid)  # e.g 12971

# Get pids by program name
program_name = 'chrome'
process_pids = [ for process in psutil.process_iter() if == program_name]
print(process_pids)  # e.g [1059, 2343, ..., ..., 9645]

Function names in C++: Capitalize or not?

As others said, there is no such thing in C++. Having said that, I tend to use the style in which the standard library is written - K & R.

Also, see the FAQ entry by Bjarne Stroustrup.

Use of REPLACE in SQL Query for newline/ carriage return characters

There are probably embedded tabs (CHAR(9)) etc. as well. You can find out what other characters you need to replace (we have no idea what your goal is) with something like this:


SET @i = 1;

SELECT @var = AccountType FROM dbo.Account
  WHERE AccountNumber = 200
  AND AccountType LIKE '%Daily%';


WHILE @i <= LEN(@var)
  INSERT #x 
    SELECT SUBSTRING(@var, @i, 1), ASCII(SUBSTRING(@var, @i, 1));

  SET @i = @i + 1;


You might also consider doing better cleansing of this data before it gets into your database. Cleaning it every time you need to search or display is not the best approach.

Rotate and translate

The reason is because you are using the transform property twice. Due to CSS rules with the cascade, the last declaration wins if they have the same specificity. As both transform declarations are in the same rule set, this is the case.

What it is doing is this:

  1. rotate the text 90 degrees. Ok.
  2. translate 50% by 50%. Ok, this is same property as step one, so do this step and ignore step 1.

See and open it in the debugger to see the first declaration overwritten

As the translate is overwriting the rotate, you have to combine them in the same declaration instead:

To do this you use a space separated list of transforms:

#rotatedtext {
    transform-origin: left;
    transform: translate(50%, 50%) rotate(90deg) ;

Remember that they are specified in a chain, so the translate is applied first, then the rotate after that.

Grant Select on a view not base table when base table is in a different database

You can grant permissions on a view and not the base table. This is one of the reasons people like using views.

Have a look here: GRANT Object Permissions (Transact-SQL)

Django Rest Framework File Upload

Finally I am able to upload image using Django. Here is my working code

class FileUploadView(APIView):
    parser_classes = (FileUploadParser, )

    def post(self, request, format='jpg'):
        up_file = request.FILES['file']
        destination = open('/Users/Username/' +, 'wb+')
        for chunk in up_file.chunks():
        destination.close()  # File should be closed only after all chuns are added

        # ...
        # do some stuff with uploaded file
        # ...
        return Response(, status.HTTP_201_CREATED)

urlpatterns = patterns('', 
url(r'^imageUpload', views.FileUploadView.as_view())

curl request to upload

curl -X POST -S -H -u "admin:password" -F "[email protected];type=image/jpg"

Count number of occurrences for each unique value

If i am understanding your question, would this work? (you will have to replace with your actual column and table names)

SELECT time_col, COUNT(time_col) As Count
FROM time_table
GROUP BY time_col
WHERE activity_col = 3

outline on only one border

I know this is old. But yeah. I prefer much shorter solution, than Giona answer

[contenteditable] {
    border-bottom: 1px solid transparent;
    &:focus {outline: none; border-bottom: 1px dashed #000;}

org.hibernate.MappingException: Unknown entity

In hibernate.cfg.xml , please put following code

<mapping class="class/bo name"/>

Div Size Automatically size of content

If display: inline; isn't working, try out display: inline-block;. :)

How to change default language for SQL Server?

Please try below:

SET @Today = '12/5/2007';  

SELECT DATENAME(month, @Today) AS 'Month Name';  

SET LANGUAGE us_english;  
SELECT DATENAME(month, @Today) AS 'Month Name' ;  


Immediate exit of 'while' loop in C++

Yah Im pretty sure you just put


right where you want it to exit


    if (variable == 1)
    //do something

Fast ceiling of an integer division in C / C++

I would have rather commented but I don't have a high enough rep.

As far as I am aware, for positive arguments and a divisor which is a power of 2, this is the fastest way (tested in CUDA):

//example y=8
q = (x >> 3) + !!(x & 7);

For generic positive arguments only, I tend to do it like so:

q = x/y + !!(x % y);

HTML entity for check mark

Something like this?

if so, type the HTML &#10004;

And &#10003; gives a lighter one:

How to get file path from OpenFileDialog and FolderBrowserDialog?

I am sorry if i am late to reply here but i just thought i should throw in a much simpler solution for the OpenDialog.

OpenDialog ofd = new OpenDialog();
var fullPathIncludingFileName = ofd.Filename; //returns the full path including the filename
var fullPathExcludingFileName = ofd.Filename.Replace(ofd.SafeFileName, "");//will remove the filename from the full path

I have not yet used a FolderBrowserDialog before so i will trust my fellow coders's take on this. I hope this helps.

Counting Line Numbers in Eclipse

Under linux, the simpler is:

  1. go to the root folder of your project
  2. use find to do a recursive search of *.java files
  3. use wc -l to count lines:

To resume, just do:

find . -name '*.java' | xargs wc -l    

Request string without GET arguments

I know this is an old post but I am having the same problem and I solved it this way

$current_request = preg_replace("/\?.*$/","",$_SERVER["REQUEST_URI"]);

Or equivalently

$current_request = preg_replace("/\?.*/D","",$_SERVER["REQUEST_URI"]);

How to check if two words are anagrams

A way to solve this - based on Sai Kiran's answer..

import java.util.Scanner;

public class Anagram {
    public static void main(String[] args) {
        Scanner sc = new Scanner(;

        System.out.print("Enter first word : ");
        String word1 = sc.nextLine();
        System.out.print("Enter second word : ");
        String word2 = sc.nextLine();


        System.out.println("Is Anagram : " + isAnagram(word1, word2));

    private static boolean isAnagram(String word1, String word2) {

        if (word1.length() != word2.length()) {
            System.err.println("Words length didn't match!");
            return false;

        char ch1, ch2;
        int len = word1.length(), sumOfWord1Chars = 0, sumOfWord2Chars = 0;

        for (int i = 0; i < len; i++) {
            ch1 = word1.charAt(i);
            if (word2.indexOf(ch1) < 0) {
                System.err.println("'" + ch1 + "' not found in \"" + word2
                        + "\"");
                return false;
            sumOfWord1Chars += word1.charAt(i);

            ch2 = word2.charAt(i);
            if (word1.indexOf(ch2) < 0) {
                System.err.println("'" + ch2 + "' not found in \"" + word1
                        + "\"");
                return false;
            sumOfWord2Chars += word2.charAt(i);

        if (sumOfWord1Chars != sumOfWord2Chars) {
                    .println("Sum of both words didn't match, i.e., words having same characters but with different counts!");
            return false;

        return true;

Check if page gets reloaded or refreshed in JavaScript

Append the below Script in Console:

window.addEventListener("beforeunload", function(event) { 
     console.log("The page is redirecting")           

Where can I download IntelliJ IDEA Color Schemes?

Since it is hard to find good themes for IntelliJ IDEA, I've created this site: (note: site archived to GitHub repo) where there is a large collection of themes. There are 270 themes for now and the site is growing.

Screenshot of the site

P.S.: Help me and other people — do not forget to upvote when you download themes from this site!

ASP.Net MVC: Calling a method from a view

why You don't use Ajax to

its simple and does not require page refresh and has success and error callbacks

take look at my samlpe

<a id="ResendVerificationCode" >@Resource_en.ResendVerificationCode</a>

and in JQuery

 $("#ResendVerificationCode").on("click", function() {

and this is my ajax which call my controller and my controller and return object from database

function getUserbyPhoneIfNotRegisterd(userphone) {

                    type: "GET",
                    dataType: "Json",
                    url: '@Url.Action("GetUserByPhone", "User")' + '?phone=' + userphone,
                    async: false,
                    success: function(data) {
                        if (data == null || == null) {
                            ErrorMessage("", "@Resource_en.YourPhoneDoesNotExistInOurDatabase");
                        } else {
                            user = data[Object.keys(data)[0]];
                                AddVereCode(user.ID);// anather Ajax call 
                                SuccessMessage("Done", "@Resource_en.VerificationCodeSentSuccessfully", "Done");
                    error: function() {
                        ErrorMessage("", '@Resource_en.ErrorOccourd');

Single selection in RecyclerView

Looks like there are two things at play here:

(1) The views are reused, so the old listener is still present.

(2) You are changing the data without notifying the adapter of the change.

I will address each separately.

(1) View reuse

Basically, in onBindViewHolder you are given an already initialized ViewHolder, which already contains a view. That ViewHolder may or may not have been previously bound to some data!

Note this bit of code right here:


If the holder has been previously bound, then the checkbox already has a listener for when the checked state changes! That listener is being triggered at this point, which is what was causing your IllegalStateException.

An easy solution would be to remove the listener before calling setChecked. An elegant solution would require more knowledge of your views - I encourage you to look for a nicer way of handling this.

(2) Notify the adapter when data changes

The listener in your code is changing the state of the data without notifying the adapter of any subsequent changes. I don't know how your views are working so this may or may not be an issue. Typically when the state of your data changes, you need to let the adapter know about it.

RecyclerView.Adapter has many options to choose from, including notifyItemChanged, which tells it that a particular item has changed state. This might be good for your use

if(isChecked) {
    for (int i = 0; i < fonts.size(); i++) {
        if (i == position) continue;
        Font f = fonts.get(i);
        if (f.isSelected()) {
            notifyItemChanged(i); // Tell the adapter this item is updated

Set timeout for webClient.DownloadFile()

Try WebClient.DownloadFileAsync(). You can call CancelAsync() by timer with your own timeout.

How to use \n new line in VB msgbox() ...?

You can use carriage return character (Chr(13)), a linefeed character (Chr(10)) also like

MsgBox "Message Name: " & objSymbol1.Name & Chr(13) & "Value of BIT-1: " & (myMessage1.Data(1)) & Chr(13) & "MessageCount: " & ReceiveMessages.Count

Android: adbd cannot run as root in production builds

You have to grant the Superuser right to the shell app ( In my case, I use Magisk to root my phone Nexsus 6P (Oreo 8.1). So I can grant Superuser right in the Magisk Manager app, whih is in the left upper option menu.

Upload File With Ajax XmlHttpRequest

  1. There is no such thing as xhr.file = file;; the file object is not supposed to be attached this way.
  2. xhr.send(file) doesn't send the file. You have to use the FormData object to wrap the file into a multipart/form-data post data object:

    var formData = new FormData();
    formData.append("thefile", file);

After that, the file can be access in $_FILES['thefile'] (if you are using PHP).

Remember, MDC and Mozilla Hack demos are your best friends.

EDIT: The (2) above was incorrect. It does send the file, but it would send it as raw post data. That means you would have to parse it yourself on the server (and it's often not possible, depend on server configuration). Read how to get raw post data in PHP here.

android: changing option menu items programmatically

Kotlin Code for accessing toolbar OptionsMenu items programmatically & change the text/icon ,..:

1-We have our menu item in menu items file like: menu.xml, sample code for this:

 <?xml version="1.0" encoding="utf-8"?> 
 <menu xmlns:android=""
<item android:id="@+id/balance"
      app:showAsAction="always" />

2- Define a variable for accessing menu object in class :

var menu: Menu? = null

3- initial it in onCreateOptionsMenu :

override fun onCreateOptionsMenu(menu: Menu): Boolean {
    // Inflate the menu; this adds items to the action bar if it is present.
    menuInflater.inflate(, menu) = menu
    return true

4- Access the menu items inside your code or fun :

private fun initialBalanceMenuItemOnToolbar() {
var menuItemBalance = menu?.findItem(
    menuItemBalance?.title = Balance?.toString() ?: 0.toString()
    // for change icon : menuWalletBalance?.icon

How to debug Javascript with IE 8

I was hoping to add this as a comment to Marcus Westin's reply, but I can't find a link - maybe I need more reputation?

Anyway, thanks, I found this code snippet useful for quick debugging in IE. I have made some quick tweaks to fix a problem that stopped it working for me, also to scroll down automatically and use fixed positioning so it will appear in the viewport. Here's my version in case anyone finds it useful:

myLog = function() {

    var _div = null;

    this.toJson = function(obj) {

        if (typeof window.uneval == 'function') { return uneval(obj); }
        if (typeof obj == 'object') {
            if (!obj) { return 'null'; }
            var list = [];
            if (obj instanceof Array) {
                    for (var i=0;i < obj.length;i++) { list.push(this.toJson(obj[i])); }
                    return '[' + list.join(',') + ']';
            } else {
                    for (var prop in obj) { list.push('"' + prop + '":' + this.toJson(obj[prop])); }
                    return '{' + list.join(',') + '}';
        } else if (typeof obj == 'string') {
            return '"' + obj.replace(/(["'])/g, '\\$1') + '"';
        } else {
            return new String(obj);


    this.createDiv = function() {

        myLog._div = document.body.appendChild(document.createElement('div'));

        var props = {
            position:'fixed', top:'10px', right:'10px', background:'#333', border:'5px solid #333', 
            color: 'white', width: '400px', height: '300px', overflow: 'auto', fontFamily: 'courier new',
            fontSize: '11px', whiteSpace: 'nowrap'

        for (var key in props) {[key] = props[key]; }


    if (!myLog._div) { this.createDiv(); }

    var logEntry = document.createElement('span');

    for (var i=0; i < arguments.length; i++) {
        logEntry.innerHTML += this.toJson(arguments[i]) + '<br />';

    logEntry.innerHTML += '<br />';


    // Scroll automatically to the bottom
    myLog._div.scrollTop = myLog._div.scrollHeight;


Difference between jQuery’s .hide() and setting CSS to display: none

They are the same thing. .hide() calls a jQuery function and allows you to add a callback function to it. So, with .hide() you can add an animation for instance.

.css("display","none") changes the attribute of the element to display:none. It is the same as if you do the following in JavaScript:

document.getElementById('elementId').style.display = 'none';

The .hide() function obviously takes more time to run as it checks for callback functions, speed, etc...

selecting unique values from a column

Use something like this in case you also want to output products details per date as JSON and the MySQL version does not support JSON functions.

SELECT `date`,
CONCAT('{',GROUP_CONCAT('{\"id\": \"',`product_id`,'\",\"name\": \"',`product_name`,'\"}'),'}') as `productsJSON`
FROM `buy` group by `date` 
order by `date` DESC

 product_id product_name     date  
|    1     |     azd    | 2011-12-12 |
|    2     |     xyz    | 2011-12-12 |
|    3     |     ase    | 2011-12-11 |
|    4     |     azwed  | 2011-12-11 |
|    5     |     wed    | 2011-12-10 |
|    6     |     cvg    | 2011-12-10 |
|    7     |     cvig   | 2011-12-09 |

       date                                productsJSON
2011-12-12T00:00:00Z    {{"id": "1","name": "azd"},{"id": "2","name": "xyz"}}
2011-12-11T00:00:00Z    {{"id": "3","name": "ase"},{"id": "4","name": "azwed"}}
2011-12-10T00:00:00Z    {{"id": "5","name": "wed"},{"id": "6","name": "cvg"}}
2011-12-09T00:00:00Z    {{"id": "7","name": "cvig"}}

Try it out in SQL Fiddle

If you are using a MySQL version that supports JSON functions then the above query could be re-written:

SELECT `date`,JSON_OBJECTAGG(CONCAT('product-',`product_id`),JSON_OBJECT('id', `product_id`, 'name', `product_name`)) as `productsJSON`
FROM `buy` group by `date`
order by `date` DESC;

Try both in DB Fiddle

Setting network adapter metric priority in Windows 7

I had the same problem on Windows 7 64-bit Pro. I adjusted network adapters binding using Control panel but nothing changed. Also metrics where showing that Win should use Ethernet adapter as primary, but it didn't.

Then a tried to uninstall Ethernet adapter driver and then install it again (without restart) and then I checked metrics for sure.

After this, Windows started prioritize Ethernet adapter.

best way to get the key of a key/value javascript object

Given your Object:

var foo = { 'bar' : 'baz' }

To get bar, use:


To get baz, use:


Assuming a single object

Change the Theme in Jupyter Notebook?

This is easy to do using the jupyter-themes package by Kyle Dunovan. You may be able to install it using conda. Otherwise, you will need to use pip.

Install it with conda:

conda install -c conda-forge jupyterthemes

or pip:

pip install jupyterthemes

You can get the list of available themes with:

jt -l

So change your theme with:

jt -t theme-name

To load a theme, finally, reload the page. The docs and source code are here.

Do you have to include <link rel="icon" href="favicon.ico" type="image/x-icon" />?

I use it for two reasons:

  1. I can force a refresh of the icon by adding a query parameter for example ?v=2. like this: <link rel="icon" href="/favicon.ico?v=2" type="image/x-icon" />

  2. In case I need to specify the path.

Opening PDF String in new window with javascript

This one worked for me."data:application/octet-stream;charset=utf-16le;base64,"+data64);

This one worked too

 let a = document.createElement("a");
 a.href = "data:application/octet-stream;base64,"+data64; = "documentName.pdf";

Push method in React Hooks (useState)?

The same way you do it with "normal" state in React class components.


function App() {
  const [state, setState] = useState([]);

  return (
      <p>You clicked {state.join(" and ")}</p>
      <button onClick={() => setState([...state, "again"])}>Click me</button>
      //old way
      <button onClick={() => setState(state.concat("again"))}>Click me</button>

Getting DOM node from React child element

This may be possible by using the refs attribute.

In the example of wanting to to reach a <div> what you would want to do is use is <div ref="myExample">. Then you would be able to get that DOM node by using React.findDOMNode(this.refs.myExample).

From there getting the correct DOM node of each child may be as simple as mapping over this.refs.myExample.children(I haven't tested that yet) but you'll at least be able to grab any specific mounted child node by using the ref attribute.

Here's the official react documentation on refs for more info.

Standard deviation of a list

I would put A_Rank et al into a 2D NumPy array, and then use numpy.mean() and numpy.std() to compute the means and the standard deviations:

In [17]: import numpy

In [18]: arr = numpy.array([A_rank, B_rank, C_rank])

In [20]: numpy.mean(arr, axis=0)
array([ 0.7       ,  2.2       ,  1.8       ,  2.13333333,  3.36666667,
        5.1       ])

In [21]: numpy.std(arr, axis=0)
array([ 0.45460606,  1.29614814,  1.37355985,  1.50628314,  1.15566239,
        1.2083046 ])


Representing complex HTML documents will be difficult and full of corner cases, but I just wanted to share a couple techniques to show how to get this kind of program started. This answer differs in that it uses data abstraction and the toJSON method to recursively build the result

Below, html2json is a tiny function which takes an HTML node as input and it returns a JSON string as the result. Pay particular attention to how the code is quite flat but it's still plenty capable of building a deeply nested tree structure – all possible with virtually zero complexity

// data Elem = Elem Node_x000D_
const Elem = e => ({_x000D_
  toJSON : () => ({_x000D_
    tagName: _x000D_
      Array.from(e.attributes, ({name, value}) => [name, value]),_x000D_
      Array.from(e.children, Elem)_x000D_
// html2json :: Node -> JSONString_x000D_
const html2json = e =>_x000D_
  JSON.stringify(Elem(e), null, '  ')_x000D_
  <h1 class="mainHeading">Some heading</h1>_x000D_
  <ul id="menu">_x000D_
    <li><a href="/a">a</a></li>_x000D_
    <li><a href="/b">b</a></li>_x000D_
    <li><a href="/c">c</a></li>_x000D_
  <p>some text</p>_x000D_

In the previous example, the textContent gets a little butchered. To remedy this, we introduce another data constructor, TextElem. We'll have to map over the childNodes (instead of children) and choose to return the correct data type based on e.nodeType – this gets us a littler closer to what we might need

// data Elem = Elem Node | TextElem Node_x000D_
const TextElem = e => ({_x000D_
  toJSON: () => ({_x000D_
const Elem = e => ({_x000D_
  toJSON : () => ({_x000D_
    tagName: _x000D_
      Array.from(e.attributes, ({name, value}) => [name, value]),_x000D_
      Array.from(e.childNodes, fromNode)_x000D_
// fromNode :: Node -> Elem_x000D_
const fromNode = e => {_x000D_
  switch (e.nodeType) {_x000D_
    case 3:  return TextElem(e)_x000D_
    default: return Elem(e)_x000D_
// html2json :: Node -> JSONString_x000D_
const html2json = e =>_x000D_
  JSON.stringify(Elem(e), null, '  ')_x000D_
  <h1 class="mainHeading">Some heading</h1>_x000D_
  <ul id="menu">_x000D_
    <li><a href="/a">a</a></li>_x000D_
    <li><a href="/b">b</a></li>_x000D_
    <li><a href="/c">c</a></li>_x000D_
  <p>some text</p>_x000D_

Anyway, that's just two iterations on the problem. Of course you'll have to address corner cases where they come up, but what's nice about this approach is that it gives you a lot of flexibility to encode the HTML however you wish in JSON – and without introducing too much complexity

In my experience, you could keep iterating with this technique and achieve really good results. If this answer is interesting to anyone and would like me to expand upon anything, let me know ^_^

Related: Recursive methods using JavaScript: building your own version of JSON.stringify

How does cookie based authentication work?

A cookie is basically just an item in a dictionary. Each item has a key and a value. For authentication, the key could be something like 'username' and the value would be the username. Each time you make a request to a website, your browser will include the cookies in the request, and the host server will check the cookies. So authentication can be done automatically like that.

To set a cookie, you just have to add it to the response the server sends back after requests. The browser will then add the cookie upon receiving the response.

There are different options you can configure for the cookie server side, like expiration times or encryption. An encrypted cookie is often referred to as a signed cookie. Basically the server encrypts the key and value in the dictionary item, so only the server can make use of the information. So then cookie would be secure.

A browser will save the cookies set by the server. In the HTTP header of every request the browser makes to that server, it will add the cookies. It will only add cookies for the domains that set them. can set a cookie and also add options in the HTTP header for the browsers to send the cookie back to subdomains, like It would be unacceptable for a browser to ever sends cookies to a different domain.

Why doesn't document.addEventListener('load', function) work in a greasemonkey script?

this happened again around last quarter of 2017 . greasemonkey firing too late . after domcontentloaded event already been fired.

what to do:

  • i used @run-at document-start instead of document-end
  • updated firefox to 57.

from :

Even as a (private) script writer I'm confused why my script isn't working.

The most likely problem is that the 'DOMContentLoaded' event is fired before the script is run. Now before you come back and say @run-at document-start is set, that directive isn't fully supported at the moment. Due to the very asynchronous nature of WebExtensions there's little guarantee on when something will be executed. When FF59 rolls around we'll have #2663 which will help. It'll actually help a lot of things, debugging too.

GIT fatal: ambiguous argument 'HEAD': unknown revision or path not in the working tree

As others pointed out, this message is coming from your shell prompt. The problem is that in a freshly created repository HEAD (.git/HEAD) points to a ref that doesn't exist yet.

% git init test
Initialized empty shared Git repository in /Users/jhelwig/tmp/test/.git/
% cd test
% cat .git/HEAD
ref: refs/heads/master
% ls -l .git/refs/heads
total 0
% git rev-parse HEAD
fatal: ambiguous argument 'HEAD': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions

It looks like rev-parse is being used without sufficient error checking before-hand. After the first commit has been created .git/refs/heads looks a bit different and git rev-parse HEAD will no longer fail.

% ls -l .git/refs/heads
total 4
-rw------- 1 jhelwig staff 41 Oct 14 16:07 master
% git rev-parse HEAD

In the function that updates the Git information for the rest of my shell prompt (heavily modified version of wunjo prompt theme for ZSH), I have the following to get around this:

zgit_info_update() {

    local gitdir=$(git rev-parse --git-dir 2>/dev/null)
    if [ $? -ne 0 ] || [ -z "$gitdir" ]; then

    # More code ...

Iterate Multi-Dimensional Array with Nested Foreach Statement

You can use an extension method like this:

internal static class ArrayExt
    public static IEnumerable<int> Indices(this Array array, int dimension)
        for (var i = array.GetLowerBound(dimension); i <= array.GetUpperBound(dimension); i++)
            yield return i;

And then:

int[,] array = { { 1, 2, 3 }, { 4, 5, 6 } };
foreach (var i in array.Indices(0))
    foreach (var j in array.Indices(1))
        Console.Write(array[i, j]);


It will be a bit slower than using for loops but probably not an issue in most cases. Not sure if it makes things more readable.

Note that c# arrays can be other than zero-based so you can use a for loop like this:

int[,] array = { { 1, 2, 3 }, { 4, 5, 6 } };
for (var i = array.GetLowerBound(0); i <= array.GetUpperBound(0); i++)
    for (var j= array.GetLowerBound(1); j <= array.GetUpperBound(1); j++)
        Console.Write(array[i, j]);


Re-run Spring Boot Configuration Annotation Processor to update generated metadata

Following these instructions worked for me:

That message about having to Re-run the Annotation Processor is a bit confusing as it appears it stays there all the time even if nothing has changed.

The key seems to be rebuilding the project after adding the required dependency, or after making any property changes. After doing that and going back to the YAML file, all my properties were now linked to the configuration classes.

You may need to click the 'Reimport All Maven Projects' button in the Maven pane as well to get the .yaml file view to recognise the links back to the corresponding Java class.

How can I delete a query string parameter in JavaScript?

From what I can see, none of the above can handle normal parameters and array parameters. Here's one that does.

function removeURLParameter(param, url) {
    url = decodeURI(url).split("?");
    path = url.length == 1 ? "" : url[1];
    path = path.replace(new RegExp("&?"+param+"\\[\\d*\\]=[\\w]+", "g"), "");
    path = path.replace(new RegExp("&?"+param+"=[\\w]+", "g"), "");
    path = path.replace(/^&/, "");
    return url[0] + (path.length
        ? "?" + path
        : "");

function addURLParameter(param, val, url) {
    if(typeof val === "object") {
        // recursively add in array structure
        if(val.length) {
            return addURLParameter(
                param + "[]",
                val.splice(-1, 1)[0],
                addURLParameter(param, val, url)
        } else {
            return url;
    } else {
        url = decodeURI(url).split("?");
        path = url.length == 1 ? "" : url[1];
        path += path.length
            ? "&"
            : "";
        path += decodeURI(param + "=" + val);
        return url[0] + "?" + path;

How to use it:

url = location.href;

url = removeURLParameter("sold", url)

url = removeURLParameter("tags", url)

url = addURLParameter("tags", ["single", "promo"], url)

url = addURLParameter("sold", 1, url)

Of course, to update a parameter, just remove then add. Feel free to make a dummy function for it.

How do I create a Java string from the contents of a file?

If you're willing to use an external library, check out Apache Commons IO (200KB JAR). It contains an method that allows you to read an entire File into a String with one line of code.


import java.nio.charset.*;

public String readFile() throws IOException {
    File file = new File("data.txt");
    return FileUtils.readFileToString(file, StandardCharsets.UTF_8);

updating nodejs on ubuntu 16.04

Difference: When I first installed node, it installed as 'nodejs'. When I upgraded it, it created 'node'. By executing node, we are actually executing nodejs. Node is just a reference to nodejs. From my experience, when I upgraded, it affected both the versions (as it is supposed to). When I do nodejs -v or node -v, I get the new version.

Upgrading: npm update is used to update the packages in the current directory. Check

To upgrade node version, based on the OS you are using, follow the commands here

How to scale images to screen size in Pygame

If you scale 1600x900 to 1280x720 you have

scale_x = 1280.0/1600
scale_y = 720.0/900

Then you can use it to find button size, and button position

button_width  = 300 * scale_x
button_height = 300 * scale_y

button_x = 1440 * scale_x
button_y = 860  * scale_y

If you scale 1280x720 to 1600x900 you have

scale_x = 1600.0/1280
scale_y = 900.0/720

and rest is the same.

I add .0 to value to make float - otherwise scale_x, scale_y will be rounded to integer - in this example to 0 (zero) (Python 2.x)

How to make/get a multi size .ico file?

ImageMagick, the free and open source image manipulation toolkit, can easily do this:

Note: Since ImageMagick 7, the CLI has changed slightly, you need to add magick in front of any commands.

magick convert icon-16.png icon-32.png icon-64.png icon-128.png icon.ico

See also, that has the example:

magick convert image.png -bordercolor white -border 0 \
          \( -clone 0 -resize 16x16 \) \
          \( -clone 0 -resize 32x32 \) \
          \( -clone 0 -resize 48x48 \) \
          \( -clone 0 -resize 64x64 \) \
          -delete 0 -alpha off -colors 256 favicon.ico

There is also now the shorter:

magick convert image.png -define icon:auto-resize="256,128,96,64,48,32,16" favicon.ico

How do you delete a column by name in data.table?

I simply do it in the data frame kind of way:

DT$col = NULL

Works fast and as far as I could see doesn't cause any problems.

UPDATE: not the best method if your DT is very large, as using the $<- operator will lead to object copying. So better use:

DT[, col:=NULL]

Clicking a checkbox with ng-click does not update the model

Replacing ng-model with ng-checked works for me.

jQuery get the image src

You may find likr


How to set timeout for a line of c# code

You can use the IAsyncResult and Action class/interface to achieve this.

public void TimeoutExample()
    IAsyncResult result;
    Action action = () =>
        // Your code here

    result = action.BeginInvoke(null, null);

    if (result.AsyncWaitHandle.WaitOne(10000))
         Console.WriteLine("Method successful.");
         Console.WriteLine("Method timed out.");

Pylint, PyChecker or PyFlakes?

Well, I am a bit curious, so I just tested the three myself right after asking the question ;-)

Ok, this is not a very serious review, but here is what I can say:

I tried the tools with the default settings (it's important because you can pretty much choose your check rules) on the following script:

# by Daniel Rosengren modified by e-satis

import sys, time
stdout = sys.stdout


class Iterator(object) :

    def __init__(self):

        print 'Rendering...'
        for y in xrange(-39, 39):
            for x in xrange(-39, 39):
                if self.mandelbrot(x/40.0, y/40.0) :
                    stdout.write(' ')

    def mandelbrot(self, x, y):
        cr = y - 0.5
        ci = x
        zi = 0.0
        zr = 0.0

        for i in xrange(MAX_ITERATIONS) :
            temp = zr * zi
            zr2 = zr * zr
            zi2 = zi * zi
            zr = zr2 - zi2 + cr
            zi = temp + temp + ci

            if zi2 + zr2 > BAILOUT:
                return i

        return 0

t = time.time()
print '\nPython Elapsed %.02f' % (time.time() - t)

As a result:

  • PyChecker is troublesome because it compiles the module to analyze it. If you don't want your code to run (e.g, it performs a SQL query), that's bad.
  • PyFlakes is supposed to be light. Indeed, it decided that the code was perfect. I am looking for something quite severe so I don't think I'll go for it.
  • PyLint has been very talkative and rated the code 3/10 (OMG, I'm a dirty coder !).

Strong points of PyLint:

  • Very descriptive and accurate report.
  • Detect some code smells. Here it told me to drop my class to write something with functions because the OO approach was useless in this specific case. Something I knew, but never expected a computer to tell me :-p
  • The fully corrected code run faster (no class, no reference binding...).
  • Made by a French team. OK, it's not a plus for everybody, but I like it ;-)

Cons of Pylint:

  • Some rules are really strict. I know that you can change it and that the default is to match PEP8, but is it such a crime to write 'for x in seq'? Apparently yes because you can't write a variable name with less than 3 letters. I will change that.
  • Very very talkative. Be ready to use your eyes.

Corrected script (with lazy doc strings and variable names):

# by Daniel Rosengren, modified by e-satis
Module doctring

import time
from sys import stdout


def mandelbrot(dim_1, dim_2):
    function doc string
    cr1 = dim_1 - 0.5
    ci1 = dim_2
    zi1 = 0.0
    zr1 = 0.0

    for i in xrange(MAX_ITERATIONS) :
        temp = zr1 * zi1
        zr2 = zr1 * zr1
        zi2 = zi1 * zi1
        zr1 = zr2 - zi2 + cr1
        zi1 = temp + temp + ci1

        if zi2 + zr2 > BAILOUT:
            return i

    return 0

def execute() :
    func doc string
    print 'Rendering...'
    for dim_1 in xrange(-39, 39):
        for dim_2 in xrange(-39, 39):
            if mandelbrot(dim_1/40.0, dim_2/40.0) :
                stdout.write(' ')

START_TIME = time.time()
print '\nPython Elapsed %.02f' % (time.time() - START_TIME)

Thanks to Rudiger Wolf, I discovered pep8 that does exactly what its name suggests: matching PEP8. It has found several syntax no-nos that Pylint did not. But Pylint found stuff that was not specifically linked to PEP8 but interesting. Both tools are interesting and complementary.

Eventually I will use both since there are really easy to install (via packages or setuptools) and the output text is so easy to chain.

To give you a little idea of their output:


./ E401 multiple imports on one line
./ E302 expected 2 blank lines, found 1
./ E203 whitespace before ':'
./ E501 line too long (108 characters)
./ W291 trailing whitespace
./ E301 expected 1 blank line, found 3


************* Module python_mandelbrot
C: 15: Line too long (108/80)
C: 61: Line too long (85/80)
C:  1: Missing docstring
C:  5: Invalid name "stdout" (should match (([A-Z_][A-Z0-9_]*)|(__.*__))$)
C: 10:Iterator: Missing docstring
C: 15:Iterator.__init__: Invalid name "y" (should match [a-z_][a-z0-9_]{2,30}$)
C: 17:Iterator.__init__: Invalid name "x" (should match [a-z_][a-z0-9_]{2,30}$)

[...] and a very long report with useful stats like :


|                         |now   |previous |difference |
|nb duplicated lines      |0     |0        |=          |
|percent duplicated lines |0.000 |0.000    |=          |

Remove Duplicates from range of cells in excel vba

To remove duplicates from a single column

 Sub removeDuplicate()
 'removeDuplicate Macro
 ActiveSheet.Range("$A$1:$A$117").RemoveDuplicates Columns:=Array(1), _ 
 End Sub

if you have header then use Header:=xlYes

Increase your range as per your requirement.
you can make it to 1000 like this :


More info here here

Why isn't textarea an input[type="textarea"]?

Maybe this is going a bit too far back but…

Also, I’d like to suggest that multiline text fields have a different type (e.g. “textarea") than single-line fields ("text"), as they really are different types of things, and imply different issues (semantics) for client-side handling.

Marc Andreessen, 11 October 1993

Powershell: count members of a AD group

Something I'd like to share..

$adinfo.members actually give twice the number of actual members. $adinfo.member (without the "s") returns the correct amount. Even when dumping $adinfo.members & $adinfo.member to screen outputs the lower amount of members.

No idea how to explain this!

What algorithm for a tic-tac-toe game can I use to determine the "best move" for the AI?

The brute force method of generating every single possible board and scoring it based on the boards it later produces further down the tree doesn't require much memory, especially once you recognize that 90 degree board rotations are redundant, as are flips about the vertical, horizontal, and diagonal axis.

Once you get to that point, there's something like less than 1k of data in a tree graph to describe the outcome, and thus the best move for the computer.


Android getting value from selected radiobutton

mRadioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
    public void onCheckedChanged(RadioGroup group, @IdRes int checkedId) {
        RadioButton radioButton = (RadioButton)group.findViewById(checkedId);

Where to place $PATH variable assertions in zsh?

tl;dr version: use ~/.zshrc

And read the man page to understand the differences between:

~/.zshrc, ~/.zshenv and ~/.zprofile.

Regarding my comment

In my comment attached to the answer kev gave, I said:

This seems to be incorrect - /etc/profile isn't listed in any zsh documentation I can find.

This turns out to be partially incorrect: /etc/profile may be sourced by zsh. However, this only occurs if zsh is "invoked as sh or ksh"; in these compatibility modes:

The usual zsh startup/shutdown scripts are not executed. Login shells source /etc/profile followed by $HOME/.profile. If the ENV environment variable is set on invocation, $ENV is sourced after the profile scripts. The value of ENV is subjected to parameter expansion, command substitution, and arithmetic expansion before being interpreted as a pathname. [man zshall, "Compatibility"].

The ArchWiki ZSH link says:

At login, Zsh sources the following files in this order:
This file is sourced by all Bourne-compatible shells upon login

This implys that /etc/profile is always read by zsh at login - I haven't got any experience with the Arch Linux project; the wiki may be correct for that distribution, but it is not generally correct. The information is incorrect compared to the zsh manual pages, and doesn't seem to apply to zsh on OS X (paths in $PATH set in /etc/profile do not make it to my zsh sessions).

To address the question:

where exactly should I be placing my rvm, python, node etc additions to my $PATH?

Generally, I would export my $PATH from ~/.zshrc, but it's worth having a read of the zshall man page, specifically the "STARTUP/SHUTDOWN FILES" section - ~/.zshrc is read for interactive shells, which may or may not suit your needs - if you want the $PATH for every zsh shell invoked by you (both interactive and not, both login and not, etc), then ~/.zshenv is a better option.

Is there a specific file I should be using (i.e. .zshenv which does not currently exist in my installation), one of the ones I am currently using, or does it even matter?

There's a bunch of files read on startup (check the linked man pages), and there's a reason for that - each file has it's particular place (settings for every user, settings for user-specific, settings for login shells, settings for every shell, etc).
Don't worry about ~/.zshenv not existing - if you need it, make it, and it will be read.

.bashrc and .bash_profile are not read by zsh, unless you explicitly source them from ~/.zshrc or similar; the syntax between bash and zsh is not always compatible. Both .bashrc and .bash_profile are designed for bash settings, not zsh settings.

How can I get the content of CKEditor using JQuery?

version 4.6


Set position / size of UI element as percentage of screen size

I think what you want is to set the android:layout_weight,

something like this (I'm just putting text views above and below as placeholders):




Count how many files in directory PHP

I use this:


How do I do word Stemming or Lemmatization?

I tried your list of terms on this snowball demo site and the results look okay....

  • cats -> cat
  • running -> run
  • ran -> ran
  • cactus -> cactus
  • cactuses -> cactus
  • community -> communiti
  • communities -> communiti

A stemmer is supposed to turn inflected forms of words down to some common root. It's not really a stemmer's job to make that root a 'proper' dictionary word. For that you need to look at morphological/orthographic analysers.

I think this question is about more or less the same thing, and Kaarel's answer to that question is where I took the second link from.

Copying files using rsync from remote server to local machine

If you have SSH access, you don't need to SSH first and then copy, just use Secure Copy (SCP) from the destination.

scp user@host:/path/file /localpath/file

Wild card characters are supported, so

scp user@host:/path/folder/* /localpath/folder

will copy all of the remote files in that folder.If copying more then one directory.

note -r will copy all sub-folders and content too.

How to mount a single file in a volume

You can also use a relative path in your docker-compose.yml file like this (tested on Windows host, Linux container):

    - ./test.conf:/fluentd/etc/test.conf

Get safe area inset top and bottom heights

In iOS 11 there is a method that tells when the safeArea has changed.

override func viewSafeAreaInsetsDidChange() {
    let top =
    let bottom = view.safeAreaInsets.bottom

When to use a linked list over an array/array list?

Hmm, Arraylist can be used in cases like follows I guess:

  1. you are not sure how many elements will be present
  2. but you need to access all the elements randomly through indexing

For eg, you need to import and access all elements in a contact list (the size of which is unknown to you)

JAVA_HOME is set to an invalid directory:

After setting the JAVA_HOME variable, run android studio as administrator

Please help me convert this script to a simple image slider

Problems only surface when I am I trying to give the first loaded content an active state

Does this mean that you want to add a class to the first button?

$('.o-links').click(function(e) {   // ... }).first().addClass('O_Nav_Current'); 

instead of using IDs for the slider's items and resetting html contents you can use classes and indexes:


.image-area {     width: 100%;     height: auto;     display: none; }  .image-area:first-of-type {     display: block; } 


var $slides = $('.image-area'),     $btns = $('a.o-links');  $btns.on('click', function (e) {     var i = $btns.removeClass('O_Nav_Current').index(this);     $(this).addClass('O_Nav_Current');      $slides.filter(':visible').fadeOut(1000, function () {         $slides.eq(i).fadeIn(1000);     });      e.preventDefault();  }).first().addClass('O_Nav_Current');

CSS word-wrapping in div

It's pretty hard to say definitively without seeing what the rendered html looks like and what styles are being applied to the elements within the treeview div, but the thing that jumps out at me right away is the

overflow-x: scroll;

What happens if you remove that?

How to center align the ActionBar title in Android?

To have a centered title in ABS (if you want to have this in the default ActionBar, just remove the "support" in the method names), you could just do this:

In your Activity, in your onCreate() method:



<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android=""

        android:textColor="#FFFFFF" />


Now you should have an Actionbar with just a title. If you want to set a custom background, set it in the Layout above (but then don't forget to set android:layout_height="match_parent").

or with:


Regex replace uppercase with lowercase letters

Before searching with regex like [A-Z], you should press the case sensitive button (or Alt+C) (as leemour nicely suggested to be edited in the accepted answer). Just to be clear, I'm leaving a few other examples:

  1. Capitalize words
    • Find: (\s)([a-z]) (\s also matches new lines, i.e. "venuS" => "VenuS")
    • Replace: $1\u$2
  2. Uncapitalize words
    • Find: (\s)([A-Z])
    • Replace: $1\l$2
  3. Remove camel case (e.g. cAmelCAse => camelcAse => camelcase)
    • Find: ([a-z])([A-Z])
    • Replace: $1\l$2
  4. Lowercase letters within words (e.g. LowerCASe => Lowercase)
    • Find: (\w)([A-Z]+)
    • Replace: $1\L$2
    • Alternate Replace: \L$0
  5. Uppercase letters within words (e.g. upperCASe => uPPERCASE)
    • Find: (\w)([A-Z]+)
    • Replace: $1\U$2
  6. Uppercase previous (e.g. upperCase => UPPERCase)
    • Find: (\w+)([A-Z])
    • Replace: \U$1$2
  7. Lowercase previous (e.g. LOWERCase => lowerCase)
    • Find: (\w+)([A-Z])
    • Replace: \L$1$2
  8. Uppercase the rest (e.g. upperCase => upperCASE)
    • Find: ([A-Z])(\w+)
    • Replace: $1\U$2
  9. Lowercase the rest (e.g. lOWERCASE => lOwercase)
    • Find: ([A-Z])(\w+)
    • Replace: $1\L$2
  10. Shift-right-uppercase (e.g. Case => cAse => caSe => casE)
    • Find: ([a-z\s])([A-Z])(\w)
    • Replace: $1\l$2\u$3
  11. Shift-left-uppercase (e.g. CasE => CaSe => CAse => Case)
    • Find: (\w)([A-Z])([a-z\s])
    • Replace: \u$1\l$2$3

Regarding the question (match words with at least one uppercase and one lowercase letter and make them lowercase), leemour's comment-answer is the right answer. Just to clarify, if there is only one group to replace, you can just use ?: in the inner groups (i.e. non capture groups) or avoid creating them at all:

  • Find: ((?:[a-z][A-Z]+)|(?:[A-Z]+[a-z])) OR ([a-z][A-Z]+|[A-Z]+[a-z])
  • Replace: \L$1

2016-06-23 Edit

Tyler suggested by editing this answer an alternate find expression for #4:

  • (\B)([A-Z]+)

According to the documentation, \B will look for a character that is not at the word's boundary (i.e. not at the beginning and not at the end). You can use the Replace All button and it does the exact same thing as if you had (\w)([A-Z]+) as the find expression.

However, the downside of \B is that it does not allow single replacements, perhaps due to the find's "not boundary" restriction (please do edit this if you know the exact reason).

Difference between / and /* in servlet mapping url pattern

I think Candy's answer is mostly correct. There is one small part I think otherwise.

To map host:port/context/hello.jsp

  1. No exact URL servlets installed, next.
  2. Found wildcard paths servlets, return.

I believe that why "/*" does not match host:port/context/hello because it treats "/hello" as a path instead of a file (since it does not have an extension).

JavaScript: how to change form action attribute value based on selection?

Simple and easy in javascipt


  document.getElementById("selectsearch").addEventListener("change", function(){

  var get_form =   document.getElementById("search-form") // get form 
  get_form.action =  '/search/' +  this.value; // assign value 



How to fit Windows Form to any screen resolution?

You can simply set the window state

this.WindowState = System.Windows.Forms.FormWindowState.Maximized;

Best way to run scheduled tasks

You can easily create a Windows Service that runs code on interval using the 'ThreadPool.RegisterWaitForSingleObject' method. It is really slick and quite easy to get set up. This method is a more streamlined approach then to use any of the Timers in the Framework.

Have a look at the link below for more information:

Running a Periodic Process in .NET using a Windows Service:

What does "async: false" do in jQuery.ajax()?


Synchronous XMLHttpRequest outside of workers is in the process of being removed from the web platform as it has detrimental effects to the end user's experience. (This is a long process that takes many years.) Developers must not pass false for the async argument when the JavaScript global environment is a document environment. User agents are strongly encouraged to warn about such usage in developer tools and may experiment with throwing an InvalidAccessError exception when it occurs. The future direction is to only allow XMLHttpRequests in worker threads. The message is intended to be a warning to that effect.

What is the default lifetime of a session?

Check out php.ini the value set for session.gc_maxlifetime is the ID lifetime in seconds.

I believe the default is 1440 seconds (24 mins)

Edit: As some comments point out, the above is not entirely accurate. A wonderful explanation of why, and how to implement session lifetimes is available here:

How do I expire a PHP session after 30 minutes?

How do I read an image file using Python?

The word "read" is vague, but here is an example which reads a jpeg file using the Image class, and prints information about it.

from PIL import Image
jpgfile ="picture.jpg")

print(jpgfile.bits, jpgfile.size, jpgfile.format)

In Go's http package, how do I get the query string on a POST request?

Here's a more concrete example of how to access GET parameters. The Request object has a method that parses them out for you called Query:

Assuming a request URL like http://host:port/something?param1=b

func newHandler(w http.ResponseWriter, r *http.Request) {
  fmt.Println("GET params were:", r.URL.Query())

  // if only one expected
  param1 := r.URL.Query().Get("param1")
  if param1 != "" {
    // ... process it, will be the first (only) if multiple were given
    // note: if they pass in like ?param1=&param2= param1 will also be "" :|

  // if multiples possible, or to process empty values like param1 in
  // ?param1=&param2=something
  param1s := r.URL.Query()["param1"]
  if len(param1s) > 0 {
    // ... process them ... or you could just iterate over them without a check
    // this way you can also tell if they passed in the parameter as the empty string
    // it will be an element of the array that is the empty string

Also note "the keys in a Values map [i.e. Query() return value] are case-sensitive."