Programs & Examples On #Node.js

Node.js is an event-based, non-blocking, asynchronous I/O framework that uses Google's V8 JavaScript engine and libuv library. It is used for developing applications that make heavy use of the ability to run JavaScript both on the client, as well as on server side and therefore benefit from the re-usability of code and the lack of context switching.

How can I check if a JSON is empty in NodeJS?

Object.keys(myObj).length === 0;

As there is need to just check if Object is empty it will be better to directly call a native method Object.keys(myObj).length which returns the array of keys by internally iterating with for..in loop.As Object.hasOwnProperty returns a boolean result based on the property present in an object which itself iterates with for..in loop and will have time complexity O(N2).

On the other hand calling a UDF which itself has above two implementations or other will work fine for small object but will block the code which will have severe impact on overall perormance if Object size is large unless nothing else is waiting in the event loop.

nodejs mysql Error: Connection lost The server closed the connection

Creating and destroying the connections in each query maybe complicated, i had some headaches with a server migration when i decided to install MariaDB instead MySQL. For some reason in the file etc/my.cnf the parameter wait_timeout had a default value of 10 sec (it causes that the persistence can't be implemented). Then, the solution was set it in 28800, that's 8 hours. Well, i hope help somebody with this "güevonada"... excuse me for my bad english.

How to get GET (query string) variables in Express.js on Node.js?

You should be able to do something like this:

var http = require('http');
var url  = require('url');

http.createServer(function(req,res){
    var url_parts = url.parse(req.url, true);
    var query = url_parts.query;

    console.log(query); //{Object}

    res.end("End")
})

Is it possible to pass a flag to Gulp to have it run tasks in different ways?

And if you are using typescript (gulpfile.ts) then do this for yargs (building on @Caio Cunha's excellent answer https://stackoverflow.com/a/23038290/1019307 and other comments above):

Install

npm install --save-dev yargs

typings install dt~yargs --global --save

.ts files

Add this to the .ts files:

import { argv } from 'yargs';

...

  let debug: boolean = argv.debug;

This has to be done in each .ts file individually (even the tools/tasks/project files that are imported into the gulpfile.ts/js).

Run

gulp build.dev --debug

Or under npm pass the arg through to gulp:

npm run build.dev -- --debug

await is only valid in async function

I had the same problem and the following block of code was giving the same error message:

repositories.forEach( repo => {
        const commits = await getCommits(repo);
        displayCommit(commits);
});

The problem is that the method getCommits() was async but I was passing it the argument repo which was also produced by a Promise. So, I had to add the word async to it like this: async(repo) and it started working:

repositories.forEach( async(repo) => {
        const commits = await getCommits(repo);
        displayCommit(commits);
});

How could others, on a local network, access my NodeJS app while it's running on my machine?

var http = require('http');
http.createServer(function (req, res) {
}).listen(80, '127.0.0.1');
console.log('Server running at http://127.0.0.1:80/');

The difference between "require(x)" and "import x"

The major difference between require and import, is that require will automatically scan node_modules to find modules, but import, which comes from ES6, won't.

Most people use babel to compile import and export, which makes import act the same as require.

The future version of Node.js might support import itself (actually, the experimental version already does), and judging by Node.js' notes, import won't support node_modules, it base on ES6, and must specify the path of the module.

So I would suggest you not use import with babel, but this feature is not yet confirmed, it might support node_modules in the future, who would know?


For reference, below is an example of how babel can convert ES6's import syntax to CommonJS's require syntax.

Say the fileapp_es6.js contains this import:

import format from 'date-fns/format';

This is a directive to import the format function from the node package date-fns.

The related package.json file could contain something like this:

"scripts": {
    "start": "node app.js",
    "build-server-file": "babel app_es6.js --out-file app.js",
    "webpack": "webpack"
}

The related .babelrc file could be something like this:

{
    "presets": [
        [
            "env",
            {
                "targets":
                {
                    "node": "current"
                }
            }
        ]
    ]
}

This build-server-file script defined in the package.json file is a directive for babel to parse the app_es6.js file and output the file app.js.

After running the build-server-file script, if you open app.js and look for the date-fns import, you will see it has been converted into this:

var _format = require("date-fns/format");

var _format2 = _interopRequireDefault(_format);

Most of that file is gobbledygook to most humans, however computers understand it.


Also for reference, as an example of how a module can be created and imported into your project, if you install date-fns and then open node_modules/date-fns/get_year/index.js you can see it contains:

var parse = require('../parse/index.js')

function getYear (dirtyDate) {
  var date = parse(dirtyDate)
  var year = date.getFullYear()
  return year
}

module.exports = getYear

Using the babel process above, your app_es6.js file could then contain:

import getYear from 'date-fns/get_year';

// Which year is 2 July 2014?
var result = getYear(new Date(2014, 6, 2))
//=> 2014

And babel would convert the imports to:

var _get_year = require("date-fns/get_year");

var _get_year2 = _interopRequireDefault(_get_year);

And handle all references to the function accordingly.

Mongodb: failed to connect to server on first connect

I was getting same error while I tried to connect mlab db that is because my organization network has some restriction, I switched to mobile hotspot and it worked.

How to create a directory if it doesn't exist using Node.js?

fs.exist() is deprecated. So I have used fs.stat() to check the directory status. If the directory does not exist fs.stat() throw an error with message like 'no such file or directory'. Then I have created a directory.

const fs = require('fs').promises;
    
const dir = './dir';
fs.stat(dir).catch(async (err) => {
  if (err.message.includes('no such file or directory')) {
    await fs.mkdir(dir);
  }
});

How to format a UTC date as a `YYYY-MM-DD hh:mm:ss` string using NodeJS?

I needed a simple formatting library without the bells and whistles of locale and language support. So I modified

http://www.mattkruse.com/javascript/date/date.js

and used it. See https://github.com/adgang/atom-time/blob/master/lib/dateformat.js

The documentation is pretty clear.

Properly close mongoose's connection once you're done

You can close the connection with

mongoose.connection.close()

JavaScript OOP in NodeJS: how?

This is the best video about Object-Oriented JavaScript on the internet:

The Definitive Guide to Object-Oriented JavaScript

Watch from beginning to end!!

Basically, Javascript is a Prototype-based language which is quite different than the classes in Java, C++, C#, and other popular friends. The video explains the core concepts far better than any answer here.

With ES6 (released 2015) we got a "class" keyword which allows us to use Javascript "classes" like we would with Java, C++, C#, Swift, etc.

Screenshot from the video showing how to write and instantiate a Javascript class/subclass: enter image description here

Mongoose: CastError: Cast to ObjectId failed for value "[object Object]" at path "_id"

Had the same problem, I just coerced the id into a string.

My schema:

const product = new mongooseClient.Schema({
    retailerID: { type: mongoose.SchemaTypes.ObjectId, required: true, index: true }
});

And then, when inserting:

retailerID: `${retailer._id}`

The best node module for XML parsing

You can try xml2js. It's a simple XML to JavaScript object converter. It gets your XML converted to a JS object so that you can access its content with ease.

Here are some other options:

  1. libxmljs
  2. xml-stream
  3. xmldoc
  4. cheerio – implements a subset of core jQuery for XML (and HTML)

I have used xml2js and it has worked fine for me. The rest you might have to try out for yourself.

How to use font-awesome icons from node-modules

SASS modules version

Soon, using @import in sass will be depreciated. SASS modules configuration works using @use instead.

@use "../node_modules/font-awesome/scss/font-awesome"  with (
  $fa-font-path: "../icons"
);

.icon-user {
  @extend .fa;
  @extend .fa-user;
}

Find the version of an installed npm package

If you agree to install jq, you can use the JSON output of npm list.

npm -j ls <package-name> | jq -r .version

or, if you want to be verbose

npm --json list <package-name> | jq --raw-output '.version'

For instance:

$ npm -j ls ghost | jq -r .version
0.4.2

Also, the JSON format is slightly different for global packages, so you'll need to change the query.

For instance:

$ npm -j -g ls | jq -r .dependencies.ghost.version
0.4.2

How to write asynchronous functions for Node.js

Just passing by callbacks is not enough. You have to use settimer for example, to make function async.

Examples: Not async functions:

function a() {
  var a = 0;    
  for(i=0; i<10000000; i++) {
    a++;
  };
  b();
};

function b() {
  var a = 0;    
  for(i=0; i<10000000; i++) {
    a++;
  };    
  c();
};

function c() {
  for(i=0; i<10000000; i++) {
  };
  console.log("async finished!");
};

a();
console.log("This should be good");

If you will run above example, This should be good, will have to wait untill those functions will finish to work.

Pseudo multithread (async) functions:

function a() {
  setTimeout ( function() {
    var a = 0;  
    for(i=0; i<10000000; i++) {
      a++;
    };
    b();
  }, 0);
};

function b() {
  setTimeout ( function() {
    var a = 0;  
    for(i=0; i<10000000; i++) {
      a++;
    };  
    c();
  }, 0);
};

function c() {
  setTimeout ( function() {
    for(i=0; i<10000000; i++) {
    };
    console.log("async finished!");
  }, 0);
};

a();
console.log("This should be good");

This one will be trully async. This should be good will be writen before async finished.

nodejs npm global config missing on windows

For me (being on Windows 10) the npmrc file was located in:

%USERPROFILE%\.npmrc

Tested with:

  • npm v4.2.0
  • Node.js v7.8.0

Doing a cleanup action just before Node.js exits

io.js has an exit and a beforeExit event, which do what you want.

Can not find module “@angular-devkit/build-angular”

D:project/contactlist npm install then D:project/contactlist ng new client

D:project/contactlist/client ng serve

this worked for me for some reason i had to delete the client folder and start npm install from the contactlist folder. i tried every thing even clearing the cache and finally this worked.

Difference between app.use and app.get in express.js

app.use() is intended for binding middleware to your application. The path is a "mount" or "prefix" path and limits the middleware to only apply to any paths requested that begin with it. It can even be used to embed another application:

// subapp.js
var express = require('express');
var app = modules.exports = express();
// ...
// server.js
var express = require('express');
var app = express();

app.use('/subapp', require('./subapp'));

// ...

By specifying / as a "mount" path, app.use() will respond to any path that starts with /, which are all of them and regardless of HTTP verb used:

  • GET /
  • PUT /foo
  • POST /foo/bar
  • etc.

app.get(), on the other hand, is part of Express' application routing and is intended for matching and handling a specific route when requested with the GET HTTP verb:

  • GET /

And, the equivalent routing for your example of app.use() would actually be:

app.all(/^\/.*/, function (req, res) {
    res.send('Hello');
});

(Update: Attempting to better demonstrate the differences.)

The routing methods, including app.get(), are convenience methods that help you align responses to requests more precisely. They also add in support for features like parameters and next('route').

Within each app.get() is a call to app.use(), so you can certainly do all of this with app.use() directly. But, doing so will often require (probably unnecessarily) reimplementing various amounts of boilerplate code.

Examples:

  • For simple, static routes:

    app.get('/', function (req, res) {
      // ...
    });
    

    vs.

    app.use('/', function (req, res, next) {
      if (req.method !== 'GET' || req.url !== '/')
        return next();
    
      // ...
    });
    
  • With multiple handlers for the same route:

    app.get('/', authorize('ADMIN'), function (req, res) {
      // ...
    });
    

    vs.

    const authorizeAdmin = authorize('ADMIN');
    
    app.use('/', function (req, res, next) {
      if (req.method !== 'GET' || req.url !== '/')
        return next();
    
      authorizeAdmin(req, res, function (err) {
        if (err) return next(err);
    
        // ...
      });
    });
    
  • With parameters:

    app.get('/item/:id', function (req, res) {
      let id = req.params.id;
      // ...
    });
    

    vs.

    const pathToRegExp = require('path-to-regexp');
    
    function prepareParams(matches, pathKeys, previousParams) {
      var params = previousParams || {};
    
      // TODO: support repeating keys...
      matches.slice(1).forEach(function (segment, index) {
        let { name } = pathKeys[index];
        params[name] = segment;
      });
    
      return params;
    }
    
    const itemIdKeys = [];
    const itemIdPattern = pathToRegExp('/item/:id', itemIdKeys);
    
    app.use('/', function (req, res, next) {
      if (req.method !== 'GET') return next();
    
      var urlMatch = itemIdPattern.exec(req.url);
      if (!urlMatch) return next();
    
      if (itemIdKeys && itemIdKeys.length)
        req.params = prepareParams(urlMatch, itemIdKeys, req.params);
    
      let id = req.params.id;
      // ...
    });
    

Note: Express' implementation of these features are contained in its Router, Layer, and Route.

Install dependencies globally and locally using package.json

You could use a separate file, like npm_globals.txt, instead of package.json. This file would contain each module on a new line like this,

[email protected]
[email protected]
[email protected]
[email protected]
[email protected]

Then in the command line run,

< npm_globals.txt xargs npm install -g

Check that they installed properly with,

npm list -g --depth=0

As for whether you should do this or not, I think it all depends on use case. For most projects, this isn't necessary; and having your project's package.json encapsulate these tools and dependencies together is much preferred.

But nowadays I find that I'm always installing create-react-app and other CLI's globally when I jump on a new machine. It's nice to have an easy way to install a global tool and its dependencies when versioning doesn't matter much.

And nowadays, I'm using npx, an npm package runner, instead of installing packages globally.

Specify path to node_modules in package.json

Yarn supports this feature:

# .yarnrc file in project root
--modules-folder /node_modules

But your experience can vary depending on which packages you use. I'm not sure you'd want to go into that rabbit hole.

Copy folder recursively in Node.js

For a Linux/Unix OS, you can use the shell syntax

const shell = require('child_process').execSync;

const src = `/path/src`;
const dist = `/path/dist`;

shell(`mkdir -p ${dist}`);
shell(`cp -r ${src}/* ${dist}`);

That's it!

Determine command line working directory when running node bin script

Here's what worked for me:

console.log(process.mainModule.filename);

ECONNREFUSED error when connecting to mongodb from node.js

I had the same issue. What I did is to run mongodb command in another terminal. Then, run my application in another tab. This resolved my problem. Though, I am trying other solution such as creating a script to run mongodb before connection is made.

How to create a simple http proxy in node.js?

I juste wrote a proxy in nodejs that take care of HTTPS with optional decoding of the message. This proxy also can add proxy-authentification header in order to go through a corporate proxy. You need to give as argument the url to find the proxy.pac file in order to configurate the usage of corporate proxy.

https://github.com/luckyrantanplan/proxy-to-proxy-https

How to change bower's default components folder?

I had the same issue on my windows 10. This is what fixed my problem

  1. Delete bower_components in your root folder
  2. Create a .bowerrc file in the root
  3. In the file write this code {"directory" : "public/bower_components"}
  4. Run a bower install

You should see bower_components folder in your public folder now

Apache and Node.js on the Same Server


Instructions to run node server along apache2(v2.4.xx) server:

In order to pipe all requests on a particular URL to your Node.JS application create CUSTOM.conf file inside /etc/apache2/conf-available directory, and add following line to the created file:

ProxyPass /node http://localhost:8000/

Change 8000 to the prefered port number for node server.
Enable custom configurations with following command:

$> sudo a2enconf CUSTOM

CUSTOM is your newly created filename without extension, then enable proxy_http with the command:

$> sudo a2enmod proxy_http

it should enable both proxy and proxy_http modules. You can check whether module is enabled or not with:

$> sudo a2query -m MODULE_NAME

After configuration and modules enabled, you will need to restart apache server:

$> sudo service apache2 restart

Now you can execute node server. All requests to the URL/node will be handled by node server.

How to pass variable from jade template file to a script file?

See this question: JADE + EXPRESS: Iterating over object in inline JS code (client-side)?

I'm having the same problem. Jade does not pass local variables in (or do any templating at all) to javascript scripts, it simply passes the entire block in as literal text. If you use the local variables 'address' and 'port' in your Jade file above the script tag they should show up.

Possible solutions are listed in the question I linked to above, but you can either: - pass every line in as unescaped text (!= at the beginning of every line), and simply put "-" before every line of javascript that uses a local variable, or: - Pass variables in through a dom element and access through JQuery (ugly)

Is there no better way? It seems the creators of Jade do not want multiline javascript support, as shown by this thread in GitHub: https://github.com/visionmedia/jade/pull/405

How do you reinstall an app's dependencies using npm?

The right way is to execute npm update. It's a really powerful command, it updates the missing packages and also checks if a newer version of package already installed can be used.

Read Intro to NPM to understand what you can do with npm.

Mongoose: Find, modify, save

You could also write it a little more cleaner using updateOne & $set, plus async/await.

const updateUser = async (newUser) => {
  try {
    await User.updateOne({ username: oldUsername }, {
      $set: {
        username: newUser.username,
        password: newUser.password,
        rights: newUser.rights
      }
    })
  } catch (err) {
    console.log(err)
  }
}

Since you don't need the resulting document, you can just use updateOne instead of findOneAndUpdate.

Here's a good discussion about the difference: MongoDB 3.2 - Use cases for updateOne over findOneAndUpdate

How to append to New Line in Node.js

Use the os.EOL constant instead.

var os = require("os");

function processInput ( text ) 
{     
  fs.open('H://log.txt', 'a', 666, function( e, id ) {
   fs.write( id, text + os.EOL, null, 'utf8', function(){
    fs.close(id, function(){
     console.log('file is updated');
    });
   });
  });
 }

TypeScript getting error TS2304: cannot find name ' require'

I found the solution was to use the TSD command:

tsd install node --save

Which adds/updates the typings/tsd.d.ts file and that file contains all the type definitions that are required for a node application.

At the top of my file, I put a reference to the tsd.d.ts like this:

/// <reference path="../typings/tsd.d.ts" />

The require is defined like this as of January 2016:

declare var require: NodeRequire;

interface NodeModule {
    exports: any;
    require: NodeRequireFunction;
    id: string;
    filename: string;
    loaded: boolean;
    parent: any;
    children: any[];
}

Eslint: How to disable "unexpected console statement" in Node.js?

If you're still having trouble even after configuring your package.json according to the documentation (if you've opted to use package.json to track rather than separate config files):

"rules": {
      "no-console": "off"
    },

And it still isn't working for you, don't forget you need to go back to the command line and do npm install again. :)

Automatic HTTPS connection/redirect with node.js/express

This worked for me:

app.use(function(req,res,next) {
    if(req.headers["x-forwarded-proto"] == "http") {
        res.redirect("https://[your url goes here]" + req.url, next);
    } else {
        return next();
    } 
});

Local dependency in package.json

Two steps for a complete local development:

  1. Provide the path to the local directory that contains the package.
{
  "name": "baz",
  "dependencies": {
    "bar": "file:../foo/bar"
  }
}
  1. Symlink the package folder

    cd ~/projects/node-redis    # go into the package directory
    npm link                    # creates global link
    cd ~/projects/node-bloggy   # go into some other package directory.
    npm link redis              # link-install the package
    

Remove menubar from Electron app

@"electron": "^7.1.1" : 

mainWindow = new browserWindow({ height: 500, width: 800});
//mainWindow.setAutoHideMenuBar(true);
mainWindow.autoHideMenuBar = true;

Working as expected without menu in browser.

Can't install any packages in Node.js using "npm install"

The repository is not down, it looks like they've changed how they host files (I guess they have restored some old code):

Now you have to add the /package-name/ before the -

Eg:

http://registry.npmjs.org/-/npm-1.1.48.tgz
http://registry.npmjs.org/npm/-/npm-1.1.48.tgz

There are 3 ways to solve it:

  • Use a complete mirror:
  • Use a public proxy:

    --registry http://165.225.128.50:8000

  • Host a local proxy:

    https://github.com/hughsk/npm-quickfix

git clone https://github.com/hughsk/npm-quickfix.git
cd npm-quickfix
npm set registry http://localhost:8080/
node index.js

I'd personally go with number 3 and revert to npm set registry http://registry.npmjs.org/ as soon as this get resolved.

Stay tuned here for more info: https://github.com/isaacs/npm/issues/2694

How to return a complex JSON response with Node.js?

[Edit] After reviewing the Mongoose documentation, it looks like you can send each query result as a separate chunk; the web server uses chunked transfer encoding by default so all you have to do is wrap an array around the items to make it a valid JSON object.

Roughly (untested):

app.get('/users/:email/messages/unread', function(req, res, next) {
  var firstItem=true, query=MessageInfo.find(/*...*/);
  res.writeHead(200, {'Content-Type': 'application/json'});
  query.each(function(docs) {
    // Start the JSON array or separate the next element.
    res.write(firstItem ? (firstItem=false,'[') : ',');
    res.write(JSON.stringify({ msgId: msg.fileName }));
  });
  res.end(']'); // End the JSON array and response.
});

Alternatively, as you mention, you can simply send the array contents as-is. In this case the response body will be buffered and sent immediately, which may consume a large amount of additional memory (above what is required to store the results themselves) for large result sets. For example:

// ...
var query = MessageInfo.find(/*...*/);
res.writeHead(200, {'Content-Type': 'application/json'});
res.end(JSON.stringify(query.map(function(x){ return x.fileName })));

How do I consume the JSON POST data in an Express application

For those getting an empty object in req.body

I had forgotten to set headers: {"Content-Type": "application/json"} in the request. Changing it solved the problem.

Upload a file to Amazon S3 with NodeJS

Or Using promises:

const AWS = require('aws-sdk');
AWS.config.update({
    accessKeyId: 'accessKeyId',
    secretAccessKey: 'secretAccessKey',
    region: 'region'
});

let params = {
    Bucket: "yourBucketName",
    Key: 'someUniqueKey',
    Body: 'someFile'
};
try {
    let uploadPromise = await new AWS.S3().putObject(params).promise();
    console.log("Successfully uploaded data to bucket");
} catch (e) {
    console.log("Error uploading data: ", e);
}

Folder structure for a Node.js project

It's important to note that there's no consensus on what's the best approach and related frameworks in general do not enforce nor reward certain structures.

I find this to be a frustrating and huge overhead but equally important. It is sort of a downplayed version (but IMO more important) of the style guide issue. I like to point this out because the answer is the same: it doesn't matter what structure you use as long as it's well defined and coherent.

So I'd propose to look for a comprehensive guide that you like and make it clear that the project is based on this.

It's not easy, especially if you're new to this! Expect to spend hours researching. You'll find most guides recommending an MVC-like structure. While several years ago that might have been a solid choice, nowadays that's not necessarily the case. For example here's another approach.

How to modify the nodejs request default timeout time?

I'm assuming you're using express, given the logs you have in your question. The key is to set the timeout property on server (the following sets the timeout to one second, use whatever value you want):

var server = app.listen(app.get('port'), function() {
  debug('Express server listening on port ' + server.address().port);
});
server.timeout = 1000;

If you're not using express and are only working with vanilla node, the principle is the same. The following will not return data:

var http = require('http');
var server = http.createServer(function (req, res) {
  setTimeout(function() {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello World\n');
  }, 200);
}).listen(1337, '127.0.0.1');

server.timeout = 20;
console.log('Server running at http://127.0.0.1:1337/');

Socket.IO - how do I get a list of connected sockets/clients?

As of version 1.5.1, I'm able to access all the sockets in a namespace with:

var socket_ids = Object.keys(io.of('/namespace').sockets);
socket_ids.forEach(function(socket_id) {
    var socket = io.of('/namespace').sockets[socket_id];
    if (socket.connected) {
        // Do something...
    }
});

For some reason, they're using a plain object instead of an array to store the socket IDs.

Sequelize OR condition object

In Sequelize version 5 you might also can use this way (full use Operator Sequelize) :

var condition = 
{ 
  [Op.or]: [ 
   { 
     LastName: {
      [Op.eq]: "Doe"
      },
    },
   { 
     FirstName: {
      [Op.or]: ["John", "Jane"]
      }
   },
   {
      Age:{
        [Op.gt]: 18
      }
    }
 ]
}

And then, you must include this :

const Op = require('Sequelize').Op

and pass it in :

Student.findAll(condition)
.success(function(students){ 
//
})

It could beautifully generate SQL like this :

"SELECT * FROM Student WHERE LastName='Doe' OR FirstName in ("John","Jane") OR Age>18"

Passing a variable from node.js to html

If using Express it's not necessary to use a View Engine at all, use something like this:

<h1>{{ name }} </h1>

This works if you previously set your application to use HTML instead of any View Engine

How do I parse a HTML page with Node.js

Use htmlparser2, its way faster and pretty straightforward. Consult this usage example:

https://www.npmjs.org/package/htmlparser2#usage

And the live demo here:

http://demos.forbeslindesay.co.uk/htmlparser2/

How do I move files in node.js?

This example taken from: Node.js in Action

A move() function that renames, if possible, or falls back to copying

var fs = require('fs');

module.exports = function move(oldPath, newPath, callback) {

    fs.rename(oldPath, newPath, function (err) {
        if (err) {
            if (err.code === 'EXDEV') {
                copy();
            } else {
                callback(err);
            }
            return;
        }
        callback();
    });

    function copy() {
        var readStream = fs.createReadStream(oldPath);
        var writeStream = fs.createWriteStream(newPath);

        readStream.on('error', callback);
        writeStream.on('error', callback);

        readStream.on('close', function () {
            fs.unlink(oldPath, callback);
        });

        readStream.pipe(writeStream);
    }
}

Can an AWS Lambda function call another

Kind of a roundabout solution but I just call the API endpoint for my lambda functions when I need to chain them. This allows you to decide while coding if you want them to be asynchronous or not.

In case you don't want to setup a POST request you can just setup a simple GET request with a couple, or none at all, query string parameters for easy event passing.

-- Edit --

See: https://docs.aws.amazon.com/apigateway/api-reference/making-http-requests/

and: http://docs.aws.amazon.com/lambda/latest/dg/with-on-demand-https-example.html

How can I update NodeJS and NPM to the next versions?

Updating npm is easy:

npm install npm@latest -g

nodemon command is not recognized in terminal for node js server

Just install Globally

 npm install -g  nodemon

It worked for me on Windows 10.

nodemon app.js

Determine project root from a running node.js application

__dirname will give you the root directory, as long as you're in a file that's in the root directory.

// ProjectDirectory.js (this file is in the project's root directory because you are putting it there).
module.exports = {

    root() {
        return __dirname;
    }
}

In some other file:

const ProjectDirectory = require('path/to/ProjectDirectory');
console.log(`Project root directory is ${ProjectDirectory.root}`);

Parse XLSX with Node and create json

You can also use

var XLSX = require('xlsx');
var workbook = XLSX.readFile('Master.xlsx');
var sheet_name_list = workbook.SheetNames;
console.log(XLSX.utils.sheet_to_json(workbook.Sheets[sheet_name_list[0]]))

How to add custom html attributes in JSX

if you are using es6 this should work:

<input {...{ "customattribute": "somevalue" }} />

nodejs send html file to client

After years, I want to add another approach by using a view engine in Express.js

var fs = require('fs');

app.get('/test', function(req, res, next) {
    var html = fs.readFileSync('./html/test.html', 'utf8')
    res.render('test', { html: html })
    // or res.send(html)
})

Then, do that in your views/test if you choose res.render method at the above code (I'm writing in EJS format):

<%- locals.html %>

That's all.

In this way, you don't need to break your View Engine arrangements.

How to execute an external program from within Node.js?

var exec = require('child_process').exec;
exec('pwd', function callback(error, stdout, stderr){
    // result
});

How to sort in mongoose?

This is what i did, it works fine.

User.find({name:'Thava'}, null, {sort: { name : 1 }})

What is the difference between __dirname and ./ in node.js?

The gist

In Node.js, __dirname is always the directory in which the currently executing script resides (see this). So if you typed __dirname into /d1/d2/myscript.js, the value would be /d1/d2.

By contrast, . gives you the directory from which you ran the node command in your terminal window (i.e. your working directory) when you use libraries like path and fs. Technically, it starts out as your working directory but can be changed using process.chdir().

The exception is when you use . with require(). The path inside require is always relative to the file containing the call to require.

For example...

Let's say your directory structure is

/dir1
  /dir2
    pathtest.js

and pathtest.js contains

var path = require("path");
console.log(". = %s", path.resolve("."));
console.log("__dirname = %s", path.resolve(__dirname));

and you do

cd /dir1/dir2
node pathtest.js

you get

. = /dir1/dir2
__dirname = /dir1/dir2

Your working directory is /dir1/dir2 so that's what . resolves to. Since pathtest.js is located in /dir1/dir2 that's what __dirname resolves to as well.

However, if you run the script from /dir1

cd /dir1
node dir2/pathtest.js

you get

. = /dir1
__dirname = /dir1/dir2

In that case, your working directory was /dir1 so that's what . resolved to, but __dirname still resolves to /dir1/dir2.

Using . inside require...

If inside dir2/pathtest.js you have a require call into include a file inside dir1 you would always do

require('../thefile')

because the path inside require is always relative to the file in which you are calling it. It has nothing to do with your working directory.

How can I print a circular structure in a JSON-like format?

I found circular-json library on github and it worked well for my problem.

Some good features I found useful:

  • Supports multi-platform usage but I only tested it with node.js so far.
  • API is same so all you need to do is include and use it as a JSON replacement.
  • It have it's own parsing method so you can convert the 'circular' serialized data back to object.

node.js: read a text file into an array. (Each line an item in the array.)

I had the same problem, and I have solved it with the module line-by-line

https://www.npmjs.com/package/line-by-line

At least for me works like a charm, both in synchronous and asynchronous mode.

Also, the problem with lines terminating not terminating \n can be solved with the option:

{ encoding: 'utf8', skipEmptyLines: false }

Synchronous processing of lines:

var LineByLineReader = require('line-by-line'),
    lr = new LineByLineReader('big_file.txt');

lr.on('error', function (err) {
    // 'err' contains error object
});

lr.on('line', function (line) {
    // 'line' contains the current line without the trailing newline character.
});

lr.on('end', function () {
    // All lines are read, file is closed now.
}); 

Get a json via Http Request in NodeJS

http sends/receives data as strings... this is just the way things are. You are looking to parse the string as json.

var jsonObject = JSON.parse(data);

How to parse JSON using Node.js?

How do I fix the npm UNMET PEER DEPENDENCY warning?

In case you wish to keep the current version of angular, you can visit this version compatibility checker to check which version of angular-material is best for your current angular version. You can also check peer dependencies of angular-material using angular-material compatibility.

NodeJS - What does "socket hang up" actually mean?

For request module users

Timeouts

There are two main types of timeouts: connection timeouts and read timeouts. A connect timeout occurs if the timeout is hit while your client is attempting to establish a connection to a remote machine (corresponding to the connect() call on the socket). A read timeout occurs any time the server is too slow to send back a part of the response.

Note that connection timeouts emit an ETIMEDOUT error, and read timeouts emit an ECONNRESET error.

How to set custom favicon in Express?

app.use(express.favicon(__dirname + '/public/images/favicon.ico')); 

I had it working locally without the __dirname + but couldn't get it working on my deployed server.

How to create JSON object Node.js

The other answers are helpful, but the JSON in your question isn't valid. I have formatted it to make it clearer below, note the missing single quote on line 24.

  1 {
  2     'Orientation Sensor':
  3     [
  4         {
  5             sampleTime: '1450632410296',
  6             data: '76.36731:3.4651554:0.5665419'
  7         },
  8         {
  9             sampleTime: '1450632410296',
 10             data: '78.15431:0.5247617:-0.20050584'
 11         }
 12     ],
 13     'Screen Orientation Sensor':
 14     [
 15         {
 16             sampleTime: '1450632410296',
 17             data: '255.0:-1.0:0.0'
 18         }
 19     ],
 20     'MPU6500 Gyroscope sensor UnCalibrated':
 21     [
 22         {
 23             sampleTime: '1450632410296',
 24             data: '-0.05006743:-0.013848438:-0.0063915867
 25         },
 26         {
 27             sampleTime: '1450632410296',
 28             data: '-0.051132694:-0.0127831735:-0.003325345'
 29         }
 30     ]
 31 }

There are a lot of great articles on how to manipulate objects in Javascript (whether using Node JS or a browser). I suggest here is a good place to start: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects

Nodejs cannot find installed module on Windows

For windows, everybody said you should set environment variables for nodejs and npm modules, but do you know why? For some modules, they have command line tool, after installed the module, there'are [module].cmd file in C:\Program Files\nodejs, and it's used for launch in window command. So if you don't add the path containing the cmd file to environment variables %PATH% , you won't launch them successfully through command window.

Cannot install node modules that require compilation on Windows 7 x64/VS2012

For windows 8 64-bit, installing zmq and protobuf, the following worked for me: Install Visual Studio 2012 On the command line:

SET VisualStudioVersion=11.0
npm install zmq
npm install protobuf

E: Unable to locate package npm

Download the the repository key with:

curl -s https://deb.nodesource.com/gpgkey/nodesource.gpg.key | apt-key add -

Then setup the repository:

sudo sh -c "echo deb https://deb.nodesource.com/node_8.x cosmic main \
                 > /etc/apt/sources.list.d/nodesource.list"
sudo apt-get update
sudo apt-get install nodejs

is there a require for json in node.js

JSON files don’t require an explicit exports statement. You don't need to export to use it as Javascript files.

So, you can use just require for valid JSON document.

data.json

{
  "name": "Freddie Mercury"
}

main.js

var obj = require('data.json');

console.log(obj.name); 
//Freddie Mercury

Difference between `npm start` & `node app.js`, when starting app?

From the man page, npm start:

runs a package's "start" script, if one was provided. If no version is specified, then it starts the "active" version.

Admittedly, that description is completely unhelpful, and that's all it says. At least it's more documented than socket.io.

Anyhow, what really happens is that npm looks in your package.json file, and if you have something like

"scripts": { "start": "coffee server.coffee" }

then it will do that. If npm can't find your start script, it defaults to:

node server.js

 

How to print a stack trace in Node.js?

In case someone is still looking for this like I was, then there is a module we can use called "stack-trace". It is really popular. NPM Link

Then walk through the trace.

  var stackTrace = require('stack-trace');
  .
  .
  .
  var trace = stackTrace.get();
  trace.map(function (item){ 
    console.log(new Date().toUTCString() + ' : ' +  item.toString() );  
  });

Or just simply print the trace:

var stackTrace = require('stack-trace');
.
.
.
var trace = stackTrace.get();
trace.toString();

How to make node.js require absolute? (instead of relative)

Many good answers here already. That just shows this is a common problem without clear-cut best solution. Best would be native support in Node.js of course. Here's what I use currently:

const r  = p => require (process.cwd() + p);
let see  = r ('/Subs/SubA/someFile.js' );
let see2 = r ('/Subs/SubB/someFile2.js');
...

I like this solution because the requires-section becomes shorter, no need to type 'require' many times. The main benefit of absolute paths is you can copy them from file to file without having to adjust them like you would with relative paths. Therefore copying also the extra one-liner arrow-function 'r()' is not too much extra work either. And no need to import extra npm-dependencies just to accomplish this very simple task.

How can I wait In Node.js (JavaScript)? l need to pause for a period of time

On Node 7.6.0 or higher

Node supports waiting natively:

const sleep = (waitTimeInMs) => new Promise(resolve => setTimeout(resolve, waitTimeInMs));

then if you can use async functions:

await sleep(10000); // sleep for 10 seconds

or:

sleep(10000).then(() => {
  // This will execute 10 seconds from now
});

On older Node versions (original answer)

I wanted an asynchronous sleep that worked in Windows & Linux, without hogging my CPU with a long while loop. I tried the sleep package but it wouldn't install on my Windows box. I ended up using:

https://www.npmjs.com/package/system-sleep

To install it, type:

npm install system-sleep

In your code,

var sleep = require('system-sleep');
sleep(10*1000); // sleep for 10 seconds

Works like a charm.

Writing JSON object to a JSON file with fs.writeFileSync

Make the json human readable by passing a third argument to stringify:

fs.writeFileSync('../data/phraseFreqs.json', JSON.stringify(output, null, 4));

How to add items to array in nodejs

Here is example which can give you some hints to iterate through existing array and add items to new array. I use UnderscoreJS Module to use as my utility file.

You can download from (https://npmjs.org/package/underscore)

$ npm install underscore

Here is small snippet to demonstrate how you can do it.

var _ = require("underscore");
var calendars = [1, "String", {}, 1.1, true],
    newArray = [];

_.each(calendars, function (item, index) {
    newArray.push(item);
});

console.log(newArray);

nodemon not working: -bash: nodemon: command not found

Just in case for those using Windows, you don't need sudo

npm i -g nodemon

node.js - request - How to "emitter.setMaxListeners()"?

It also happened to me

I use this code and it worked

require('events').EventEmitter.defaultMaxListeners = infinity;

Try it out. It may help

Thanks

Node.js EACCES error when listening on most ports

For me this issue affected all hosts and all ports on Windows in PowerShell.

Disabling Network Interfaces fixed the issue.

I had WiFi and an Ethernet connection and disabling the Ethernet Interface fixed this issue.

Open "Network Connections" to view your interfaces. Right-click and select "Disable".

module.exports vs exports in Node.js

exports and module.exports are the same unless you reassign exports within your module.

The easiest way to think about it, is to think that this line is implicitly at the top of every module.

var exports = module.exports = {};

If, within your module, you reassign exports, then you reassign it within your module and it no longer equals module.exports. This is why, if you want to export a function, you must do:

module.exports = function() { ... }

If you simply assigned your function() { ... } to exports, you would be reassigning exports to no longer point to module.exports.

If you don't want to refer to your function by module.exports every time, you can do:

module.exports = exports = function() { ... }

Notice that module.exports is the left most argument.

Attaching properties to exports is not the same since you are not reassigning it. That is why this works

exports.foo = function() { ... }

How to check if that data already exist in the database during update (Mongoose And Express)

In addition to already posted examples, here is another approach using express-async-wrap and asynchronous functions (ES2017).

Router

router.put('/:id/settings/profile', wrap(async function (request, response, next) {
    const username = request.body.username
    const email = request.body.email
    const userWithEmail = await userService.findUserByEmail(email)
    if (userWithEmail) {
        return response.status(409).send({message: 'Email is already taken.'})
    }
    const userWithUsername = await userService.findUserByUsername(username)
    if (userWithUsername) {
        return response.status(409).send({message: 'Username is already taken.'})
    }
    const user = await userService.updateProfileSettings(userId, username, email)
    return response.status(200).json({user: user})
}))

UserService

async function updateProfileSettings (userId, username, email) {
    try {
        return User.findOneAndUpdate({'_id': userId}, {
            $set: {
                'username': username,
                'auth.email': email
            }
        }, {new: true})
    } catch (error) {
        throw new Error(`Unable to update user with id "${userId}".`)
    }
}

async function findUserByEmail (email) {
    try {
        return User.findOne({'auth.email': email.toLowerCase()})
    } catch (error) {
        throw new Error(`Unable to connect to the database.`)
    }
}

async function findUserByUsername (username) {
    try {
        return User.findOne({'username': username})
    } catch (error) {
        throw new Error(`Unable to connect to the database.`)
    }
}

// other methods

export default {
    updateProfileSettings,
    findUserByEmail,
    findUserByUsername,
}

Resources

async function

await

express-async-wrap

Looping through JSON with node.js

You can iterate through JavaScript objects this way:

for(var attributename in myobject){
    console.log(attributename+": "+myobject[attributename]);
}

myobject could be your json.data

What is the --save option for npm install?

npm install package_x --save

The given package (package_x) will be saved in package.json inside dependencies. if you add

npm install <<package_x>> --save-dev

then it will be saved inside devDependencies.

How to get all registered routes in Express?

I have adapted an old post that is no longer online for my needs. I've used express.Router() and registered my routes like this:

var questionsRoute = require('./BE/routes/questions');
app.use('/api/questions', questionsRoute);

I renamed the document.js file in apiTable.js and adapted it like this:

module.exports =  function (baseUrl, routes) {
    var Table = require('cli-table');
    var table = new Table({ head: ["", "Path"] });
    console.log('\nAPI for ' + baseUrl);
    console.log('\n********************************************');

    for (var key in routes) {
        if (routes.hasOwnProperty(key)) {
            var val = routes[key];
            if(val.route) {
                val = val.route;
                var _o = {};
                _o[val.stack[0].method]  = [baseUrl + val.path];    
                table.push(_o);
            }       
        }
    }

    console.log(table.toString());
    return table;
};

then i call it in my server.js like this:

var server = app.listen(process.env.PORT || 5000, function () {
    require('./BE/utils/apiTable')('/api/questions', questionsRoute.stack);
});

The result looks like this:

Result example

It's just an example but might be of use.. i hope..

Node.js - SyntaxError: Unexpected token import

I'm shocked esm hasn't been mentioned. This small, but mighty package allows you to use either import or require.

Install esm in your project

$ npm install --save esm

Update your Node Start Script to use esm

node -r esm app.js

esm just works. I wasted a TON of time with .mjs and --experimental-modules only to find out a .mjs file cannot import a file that uses require or module.exports. This was a huge problem, whereas esm allows you to mix and match and it just figures it out... esm just works.

How can I check whether a variable is defined in Node.js?

Determine if property is existing (but is not a falsy value):

if (typeof query !== 'undefined' && query !== null){
   doStuff();
}

Usually using

if (query){
   doStuff();
}

is sufficient. Please note that:

if (!query){
   doStuff();
}

doStuff() will execute even if query was an existing variable with falsy value (0, false, undefined or null)

Btw, there's a sexy coffeescript way of doing this:

if object?.property? then doStuff()

which compiles to:

if ((typeof object !== "undefined" && object !== null ? object.property : void 0) != null) 

{
  doStuff();
}

How to extract request http headers from a request using NodeJS connect

To see a list of HTTP request headers, you can use :

console.log(JSON.stringify(req.headers));

to return a list in JSON format.

{
"host":"localhost:8081",
"connection":"keep-alive",
"cache-control":"max-age=0",
"accept":"text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
"upgrade-insecure-requests":"1",
"user-agent":"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.107 Safari/537.36",
"accept-encoding":"gzip, deflate, sdch",
"accept-language":"en-US,en;q=0.8,et;q=0.6"
}

Simplest way to download and unzip files in Node.js cross-platform?

Node has builtin support for gzip and deflate via the zlib module:

var zlib = require('zlib');

zlib.gunzip(gzipBuffer, function(err, result) {
    if(err) return console.error(err);

    console.log(result);
});

Edit: You can even pipe the data directly through e.g. Gunzip (using request):

var request = require('request'),
    zlib = require('zlib'),
    fs = require('fs'),
    out = fs.createWriteStream('out');

// Fetch http://example.com/foo.gz, gunzip it and store the results in 'out'
request('http://example.com/foo.gz').pipe(zlib.createGunzip()).pipe(out);

For tar archives, there is Isaacs' tar module, which is used by npm.

Edit 2: Updated answer as zlib doesn't support the zip format. This will only work for gzip.

Execute PHP scripts within Node.js web server

A simple, fast approach in my opinion would be to use dnode-php for that.

You can see a brief introduction here. Simple, quick and easy!

How to send a POST request from node.js Express?

I use superagent, which is simliar to jQuery.

Here is the docs

And the demo like:

var sa = require('superagent');
sa.post('url')
  .send({key: value})
  .end(function(err, res) {
    //TODO
  });

npm install error from the terminal

I had this problem when trying to run 'npm install' in a Terminal window which had been opened before installing Node.js.

Opening a new Terminal window (i.e. bash session) worked. (Presumably this provided the correct environment variables for npm to run correctly.)

How do I override nested NPM dependency versions?

NPM shrinkwrap offers a nice solution to this problem. It allows us to override that version of a particular dependency of a particular sub-module.

Essentially, when you run npm install, npm will first look in your root directory to see whether a npm-shrinkwrap.json file exists. If it does, it will use this first to determine package dependencies, and then falling back to the normal process of working through the package.json files.

To create an npm-shrinkwrap.json, all you need to do is

 npm shrinkwrap --dev

code:

{
  "dependencies": {
    "grunt-contrib-connect": {
      "version": "0.3.0",
      "from": "[email protected]",
      "dependencies": {
        "connect": {
          "version": "2.8.1",
          "from": "connect@~2.7.3"
        }
      }
    }
  }
}

how to specify local modules as npm package dependencies

At work we have a common library that is used by a few different projects all in a single repository. Originally we used the published (private) version (npm install --save rp-utils) but that lead to a lot of needless version updates as we developed. The library lives in a sister directory to the applications and we are able to use a relative path instead of a version. Instead of "rp-utils": "^1.3.34" in package.json it now is:

{ 
  "dependencies": { ...
    "rp-utils": "../rp-utils",
   ...

the rp-utils directory contains a publishable npm package

Loading basic HTML in Node.js

This would probably be some what better since you will be streaming the file(s) rather than loading it all into memory like fs.readFile.

var http = require('http');
var fs = require('fs');
var path = require('path');
var ext = /[\w\d_-]+\.[\w\d]+$/;

http.createServer(function(req, res){
    if (req.url === '/') {
        res.writeHead(200, {'Content-Type': 'text/html'});
        fs.createReadStream('index.html').pipe(res);
    } else if (ext.test(req.url)) {
        fs.exists(path.join(__dirname, req.url), function (exists) {
            if (exists) {
                res.writeHead(200, {'Content-Type': 'text/html'});
                fs.createReadStream('index.html').pipe(res);
            } else {
                res.writeHead(404, {'Content-Type': 'text/html'});
                fs.createReadStream('404.html').pipe(res);
        });
    } else {
        //  add a RESTful service
    }
}).listen(8000);

Docker-compose: node_modules not present in a volume after npm install succeeds

This happens because you have added your worker directory as a volume to your docker-compose.yml, as the volume is not mounted during the build.

When docker builds the image, the node_modules directory is created within the worker directory, and all the dependencies are installed there. Then on runtime the worker directory from outside docker is mounted into the docker instance (which does not have the installed node_modules), hiding the node_modules you just installed. You can verify this by removing the mounted volume from your docker-compose.yml.

A workaround is to use a data volume to store all the node_modules, as data volumes copy in the data from the built docker image before the worker directory is mounted. This can be done in the docker-compose.yml like this:

redis:
    image: redis
worker:
    build: ./worker
    command: npm start
    ports:
        - "9730:9730"
    volumes:
        - ./worker/:/worker/
        - /worker/node_modules
    links:
        - redis

I'm not entirely certain whether this imposes any issues for the portability of the image, but as it seems you are primarily using docker to provide a runtime environment, this should not be an issue.

If you want to read more about volumes, there is a nice user guide available here: https://docs.docker.com/userguide/dockervolumes/

EDIT: Docker has since changed it's syntax to require a leading ./ for mounting in files relative to the docker-compose.yml file.

How do you run a js file using npm scripts?

{ "scripts" :
  { "build": "node build.js"}
}

npm run build OR npm run-script build


{
  "name": "build",
  "version": "1.0.0",
  "scripts": {
    "start": "node build.js"
  }
}

npm start


NB: you were missing the { brackets } and the node command

folder structure is fine:

+ build
  - package.json
  - build.js

how to implement login auth in node.js

I tried this answer and it didn't work for me. I am also a newbie on web development and took classes where i used mlab but i prefer parse which is why i had to look for the most suitable solution. Here is my own current solution using parse on expressJS.

1)Check if the user is authenticated: I have a middleware function named isLogginIn which I use on every route that needs the user to be authenticated:

 function isLoggedIn(req, res, next) {
 var currentUser = Parse.User.current();
 if (currentUser) {
     next()
 } else {
     res.send("you are not authorised");
 }
}

I use this function in my routes like this:

  app.get('/my_secret_page', isLoggedIn, function (req, res) 
  {
    res.send('if you are viewing this page it means you are logged in');
  });

2) The Login Route:

  // handling login logic
  app.post('/login', function(req, res) {
  Parse.User.enableUnsafeCurrentUser();
  Parse.User.logIn(req.body.username, req.body.password).then(function(user) {
    res.redirect('/books');
  }, function(error) {
    res.render('login', { flash: error.message });
  });
});

3) The logout route:

 // logic route
  app.get("/logout", function(req, res){
   Parse.User.logOut().then(() => {
    var currentUser = Parse.User.current();  // this will now be null
    });
        res.redirect('/login');
   });

This worked very well for me and i made complete reference to the documentation here https://docs.parseplatform.org/js/guide/#users

Thanks to @alessioalex for his answer. I have only updated with the latest practices.

How do I resolve "Cannot find module" error using Node.js?

If you use nvm, check that existing node_modules that are bindings to other libraries are compiled for the correct Node.js version.

I was having the same error. The reason was the following: We use nvm since we're running two apps on a server, one requires Node.js 5.6 because it uses node-gd (which doesn't run on Node.js 6 for now), the other requires Node.js 6. Node.js 6 is the apt-get installation.

Also we use the pm2 tool to deploy.

So, the default setup is that the pm2 process starts when nvm is not in effect, so it uses the apt-get installation of Node.js (version 6). So the main pm2 daemon starts with Node.js 6. If I run applications in fork mode they start in separate processes and nvm settings are in effect. When I run applications in cluster mode - they inherit the non-nvm environment.

So when I tried to switch to the cluster mode the application failed to start because the bindings compiled for 5.6 fail with this message.

I've fixed that by restarting pm2 when nvm setings are in effect. Also startup scripts should be fixed.

Node.js, can't open files. Error: ENOENT, stat './path/to/file'

Paths specified with a . are relative to the current working directory, not relative to the script file. So the file might be found if you run node app.js but not if you run node folder/app.js. The only exception to this is require('./file') and that is only possible because require exists per-module and thus knows what module it is being called from.

To make a path relative to the script, you must use the __dirname variable.

var path = require('path');

path.join(__dirname, 'path/to/file')

or potentially

path.join(__dirname, 'path', 'to', 'file')

Uploading file using POST request in Node.js

You can also use the "custom options" support from the request library. This format allows you to create a multi-part form upload, but with a combined entry for both the file and extra form information, like filename or content-type. I have found that some libraries expect to receive file uploads using this format, specifically libraries like multer.

This approach is officially documented in the forms section of the request docs - https://github.com/request/request#forms

//toUpload is the name of the input file: <input type="file" name="toUpload">

let fileToUpload = req.file;

let formData = {
    toUpload: {
      value: fs.createReadStream(path.join(__dirname, '..', '..','upload', fileToUpload.filename)),
      options: {
        filename: fileToUpload.originalname,
        contentType: fileToUpload.mimeType
      }
    }
  };
let options = {
    url: url,
    method: 'POST',
    formData: formData
  }
request(options, function (err, resp, body) {
    if (err)
      cb(err);

    if (!err && resp.statusCode == 200) {
      cb(null, body);
    }
  });

How to properly stop the Thread in Java?

I didn't get the interrupt to work in Android, so I used this method, works perfectly:

boolean shouldCheckUpdates = true;

private void startupCheckForUpdatesEveryFewSeconds() {
    threadCheckChat = new Thread(new CheckUpdates());
    threadCheckChat.start();
}

private class CheckUpdates implements Runnable{
    public void run() {
        while (shouldCheckUpdates){
            System.out.println("Do your thing here");
        }
    }
}

 public void stop(){
        shouldCheckUpdates = false;
 }

Checkout multiple git repos into same Jenkins workspace

Checking out more than one repo at a time in a single workspace is not possible with Jenkins + Git Plugin.

As a workaround, you can either have multiple upstream jobs which checkout a single repo each and then copy to your final project workspace (Problematic on a number of levels), or you can set up a shell scripting step which checks out each needed repo to the job workspace at build time.

Previously the Multiple SCM plugin could help with this issue but it is now deprecated. From the Multiple SCM plugin page: "Users should migrate to https://wiki.jenkins-ci.org/display/JENKINS/Pipeline+Plugin . Pipeline offers a better way of checking out of multiple SCMs, and is supported by the Jenkins core development team."

How do I target only Internet Explorer 10 for certain situations like Internet Explorer-specific CSS or Internet Explorer-specific JavaScript code?

If you really have to, you can make conditional comments work by adding the following line to <head>:

<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE9">

Source

How to pass a single object[] to a params object[]

Another way to solve this problem (it's not so good practice but looks beauty):

static class Helper
{
    public static object AsSingleParam(this object[] arg)
    {
       return (object)arg;
    }
}

Usage:

f(new object[] { 1, 2, 3 }.AsSingleParam());

Powershell Active Directory - Limiting my get-aduser search to a specific OU [and sub OUs]

If I understand you correctly, you need to use -SearchBase:

Get-ADUser -SearchBase "OU=Accounts,OU=RootOU,DC=ChildDomain,DC=RootDomain,DC=com" -Filter *

Note that Get-ADUser defaults to using

 -SearchScope Subtree

so you don't need to specify it. It's this that gives you all sub-OUs (and sub-sub-OUs, etc.).

In an array of objects, fastest way to find the index of an object whose attributes match a search

The new Array method .filter() would work well for this:

var filteredArray = array.filter(function (element) { 
    return element.id === 0;
});

jQuery can also do this with .grep()

edit: it is worth mentioning that both of these functions just iterate under the hood, there won't be a noticeable performance difference between them and rolling your own filter function, but why re-invent the wheel.

CreateProcess error=2, The system cannot find the file specified

The complete first argument of exec is being interpreted as the executable. Use

p = rt.exec(new String[] {"winrar.exe", "x", "h:\\myjar.jar", "*.*", "h:\\new" }
            null, 
            dir);

Move to another EditText when Soft Keyboard Next is clicked on Android

Focus Handling

Focus movement is based on an algorithm which finds the nearest neighbor in a given direction. In rare cases, the default algorithm may not match the intended behavior of the developer.

Change default behaviour of directional navigation by using following XML attributes:

android:nextFocusDown="@+id/.."  
android:nextFocusLeft="@+id/.."    
android:nextFocusRight="@+id/.."    
android:nextFocusUp="@+id/.."  

Besides directional navigation you can use tab navigation. For this you need to use

android:nextFocusForward="@+id/.."

To get a particular view to take focus, call

view.requestFocus()

To listen to certain changing focus events use a View.OnFocusChangeListener


Keyboard button

You can use android:imeOptions for handling that extra button on your keyboard.

Additional features you can enable in an IME associated with an editor to improve the integration with your application. The constants here correspond to those defined by imeOptions.

The constants of imeOptions includes a variety of actions and flags, see the link above for their values.

Value example

ActionNext :

the action key performs a "next" operation, taking the user to the next field that will accept text.

ActionDone :

the action key performs a "done" operation, typically meaning there is nothing more to input and the IME will be closed.

Code example:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="32dp"
        android:layout_marginTop="16dp"
        android:imeOptions="actionNext"
        android:maxLines="1"
        android:ems="10" >

        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/editText2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/editText1"
        android:layout_below="@+id/editText1"
        android:layout_marginTop="24dp"
        android:imeOptions="actionDone"
        android:maxLines="1"
        android:ems="10" />

</RelativeLayout>

If you want to listen to imeoptions events use a TextView.OnEditorActionListener.

editText.setOnEditorActionListener(new TextView.OnEditorActionListener() {
    @Override
    public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
        if (actionId == EditorInfo.IME_ACTION_SEARCH) {
            performSearch();
            return true;
        }
        return false;
    }
});

AngularJS : Difference between the $observe and $watch methods

Why is $observe different than $watch?

The watchExpression is evaluated and compared to the previous value each digest() cycle, if there's a change in the watchExpression value, the watch function is called.

$observe is specific to watching for interpolated values. If a directive's attribute value is interpolated, eg dir-attr="{{ scopeVar }}", the observe function will only be called when the interpolated value is set (and therefore when $digest has already determined updates need to be made). Basically there's already a watcher for the interpolation, and the $observe function piggybacks off that.

See $observe & $set in compile.js

How to create javascript delay function

Ah yes. Welcome to Asynchronous execution.

Basically, pausing a script would cause the browser and page to become unresponsive for 3 seconds. This is horrible for web apps, and so isn't supported.

Instead, you have to think "event-based". Use setTimeout to call a function after a certain amount of time, which will continue to run the JavaScript on the page during that time.

Undoing a git rebase

Resetting the branch to the dangling commit object of its old tip is of course the best solution, because it restores the previous state without expending any effort. But if you happen to have lost those commits (f.ex. because you garbage-collected your repository in the meantime, or this is a fresh clone), you can always rebase the branch again. The key to this is the --onto switch.

Let’s say you had a topic branch imaginatively called topic, that you branched off master when the tip of master was the 0deadbeef commit. At some point while on the topic branch, you did git rebase master. Now you want to undo this. Here’s how:

git rebase --onto 0deadbeef master topic

This will take all commits on topic that aren’t on master and replay them on top of 0deadbeef.

With --onto, you can rearrange your history into pretty much any shape whatsoever.

Have fun. :-)

Playing HTML5 video on fullscreen in android webview

This is great. But if you want your website links to open in the app itself, add this code in your ExampleActivity.java:

webView.setWebViewClient(new WebViewClient() {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            if (Uri.parse(url).getHost().endsWith("yourwebsite.com")) {
                return false;
            }

            Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
            view.getContext().startActivity(intent);
            return true;
        }
    });

HTML <input type='file'> File Selection Event

Listen to the change event.

input.onchange = function(e) { 
  ..
};

Cannot deserialize instance of object out of START_ARRAY token in Spring Webservice

Your json contains an array, but you're trying to parse it as an object. This error occurs because objects must start with {.

You have 2 options:

  1. You can get rid of the ShopContainer class and use Shop[] instead

    ShopContainer response  = restTemplate.getForObject(
        url, ShopContainer.class);
    

    replace with

    Shop[] response  = restTemplate.getForObject(url, Shop[].class);
    

    and then make your desired object from it.

  2. You can change your server to return an object instead of a list

    return mapper.writerWithDefaultPrettyPrinter().writeValueAsString(list);
    

    replace with

    return mapper.writerWithDefaultPrettyPrinter().writeValueAsString(
        new ShopContainer(list));
    

Styling HTML email for Gmail

As others have said, some email programs will not read the css styles. If you already have a web email written up you can use the following tool from zurb to inline all of your styles:

http://zurb.com/ink/inliner.php

This comes in extremely handy when using templates like those mentioned above from mailchimp, campaign monitor, etc. as they, as you have found, will not work in some email programs. This tool leaves your style section for the mail programs that will read it and puts all the styles inline to get more universal readability in the format that you wanted.

How do I get DOUBLE_MAX?

Using double to store large integers is dubious; the largest integer that can be stored reliably in double is much smaller than DBL_MAX. You should use long long, and if that's not enough, you need your own arbitrary-precision code or an existing library.

Style input element to fill remaining width of its container

I suggest using Flexbox:

Be sure to add the proper vendor prefixes though!

_x000D_
_x000D_
form {_x000D_
  width: 400px;_x000D_
  border: 1px solid black;_x000D_
  display: flex;_x000D_
}_x000D_
_x000D_
input {_x000D_
  flex: 2;_x000D_
}_x000D_
_x000D_
input, label {_x000D_
  margin: 5px;_x000D_
}
_x000D_
<form method="post">_x000D_
  <label for="myInput">Sample label</label>_x000D_
  <input type="text" id="myInput" placeholder="Sample Input"/>_x000D_
</form>
_x000D_
_x000D_
_x000D_

Angular directive how to add an attribute to the element?

You can try this:

<div ng-app="app">
    <div ng-controller="AppCtrl">
        <a my-dir ng-repeat="user in users" ng-click="fxn()">{{user.name}}</a>
    </div>
</div>

<script>
var app = angular.module('app', []);

function AppCtrl($scope) {
        $scope.users = [{ name: 'John', id: 1 }, { name: 'anonymous' }];
        $scope.fxn = function () {
            alert('It works');
        };
    }

app.directive("myDir", function ($compile) {
    return {
        scope: {ngClick: '='}
    };
});
</script>

In MS DOS copying several files to one file

If this is part of a batch script (.bat file) and you have a large list of files, you can use a multi-line ^, and optional /Y flag to suppresses prompting to confirm you want to overwrite an existing destination file.

REM Concatenate several files to one
COPY /Y ^
    this_is_file_1.csv + ^
    this_is_file_2.csv + ^
    this_is_file_3.csv + ^
    this_is_file_4.csv + ^
    this_is_file_5.csv + ^
    this_is_file_6.csv + ^
    this_is_file_7.csv + ^
    this_is_file_8.csv + ^
    this_is_file_9.csv ^
        output_file.csv

This is tidier than performing the command on one line.

Add a dependency in Maven

Actually, on investigating this, I think all these answers are incorrect. Your question is misleading because of our level of understanding of maven. And I say our because I'm just getting introduced to maven.

In Eclipse, when you want to add a jar file to your project, normally you download the jar manually and then drop it into the lib directory. With maven, you don't do it this way. Here's what you do:

  • Go to mvnrepository
  • Search for the library you want to add
  • Copy the dependency statement into your pom.xml
  • rebuild via mvn

Now, maven will connect and download the jar along with the list of dependencies, and automatically resolve any additional dependencies that jar may have had. So if the jar also needed commons-logging, that will be downloaded as well.

Node.JS: Getting error : [nodemon] Internal watch failed: watch ENOSPC

Try reopening VS code or Atom with more specific directory where your app.js is present. I had a lot of folders opened and this problem occured. But once I opened my specific folder and tried once again, it worked.

Converting Date and Time To Unix Timestamp

Using a date picker to get date and a time picker I get two variables, this is how I put them together in unixtime format and then pull them out...

let datetime = oDdate+' '+oDtime;
let unixtime = Date.parse(datetime)/1000;
console.log('unixtime:',unixtime);

to prove it:

let milliseconds = unixtime * 1000;
dateObject = new Date(milliseconds);
console.log('dateObject:',dateObject);

enjoy!

Plotting multiple time series on the same plot using ggplot()

I prefer using the ggfortify library. It is a ggplot2 wrapper that recognizes the type of object inside the autoplot function and chooses the best ggplot methods to plot. At least I don't have to remember the syntax of ggplot2.

library(ggfortify)
ts1 <- 1:100
ts2 <- 1:100*0.8
autoplot(ts( cbind(ts1, ts2)  , start = c(2010,5), frequency = 12 ),
         facets = FALSE)

Plot

json.dump throwing "TypeError: {...} is not JSON serializable" on seemingly valid object?

I wrote a class to normalize the data in my dictionary. The 'element' in the NormalizeData class below, needs to be of dict type. And you need to replace in the __iterate() with either your custom class object or any other object type that you would like to normalize.

class NormalizeData:

    def __init__(self, element):
        self.element = element

    def execute(self):
        if isinstance(self.element, dict):
            self.__iterate()
        else:
            return

    def __iterate(self):
        for key in self.element:
            if isinstance(self.element[key], <ClassName>):
                self.element[key] = str(self.element[key])

            node = NormalizeData(self.element[key])
            node.execute()

What is the difference between T(n) and O(n)?

Short explanation:

If an algorithm is of T(g(n)), it means that the running time of the algorithm as n (input size) gets larger is proportional to g(n).

If an algorithm is of O(g(n)), it means that the running time of the algorithm as n gets larger is at most proportional to g(n).

Normally, even when people talk about O(g(n)) they actually mean T(g(n)) but technically, there is a difference.


More technically:

O(n) represents upper bound. T(n) means tight bound. O(n) represents lower bound.

f(x) = T(g(x)) iff f(x) = O(g(x)) and f(x) = O(g(x))

Basically when we say an algorithm is of O(n), it's also O(n2), O(n1000000), O(2n), ... but a T(n) algorithm is not T(n2).

In fact, since f(n) = T(g(n)) means for sufficiently large values of n, f(n) can be bound within c1g(n) and c2g(n) for some values of c1 and c2, i.e. the growth rate of f is asymptotically equal to g: g can be a lower bound and and an upper bound of f. This directly implies f can be a lower bound and an upper bound of g as well. Consequently,

f(x) = T(g(x)) iff g(x) = T(f(x))

Similarly, to show f(n) = T(g(n)), it's enough to show g is an upper bound of f (i.e. f(n) = O(g(n))) and f is a lower bound of g (i.e. f(n) = O(g(n)) which is the exact same thing as g(n) = O(f(n))). Concisely,

f(x) = T(g(x)) iff f(x) = O(g(x)) and g(x) = O(f(x))


There are also little-oh and little-omega (?) notations representing loose upper and loose lower bounds of a function.

To summarize:

f(x) = O(g(x)) (big-oh) means that the growth rate of f(x) is asymptotically less than or equal to to the growth rate of g(x).

f(x) = O(g(x)) (big-omega) means that the growth rate of f(x) is asymptotically greater than or equal to the growth rate of g(x)

f(x) = o(g(x)) (little-oh) means that the growth rate of f(x) is asymptotically less than the growth rate of g(x).

f(x) = ?(g(x)) (little-omega) means that the growth rate of f(x) is asymptotically greater than the growth rate of g(x)

f(x) = T(g(x)) (theta) means that the growth rate of f(x) is asymptotically equal to the growth rate of g(x)

For a more detailed discussion, you can read the definition on Wikipedia or consult a classic textbook like Introduction to Algorithms by Cormen et al.

Why SpringMVC Request method 'GET' not supported?

Change

@RequestMapping(value = "/test", method = RequestMethod.POST)

To

@RequestMapping(value = "/test", method = RequestMethod.GET)

Git: How to reset a remote Git repository to remove all commits?

First, follow the instructions in this question to squash everything to a single commit. Then make a forced push to the remote:

$ git push origin +master

And optionally delete all other branches both locally and remotely:

$ git push origin :<branch>
$ git branch -d <branch>

IF EXISTS in T-SQL

There's no need for "else" in this case:

IF EXISTS(SELECT *  FROM  table1  WHERE Name='John' ) return 1
return 0

Populate dropdown select with array using jQuery

function validateForm(){
    var success = true;
    resetErrorMessages();
    var myArray = [];
    $(".linkedServiceDonationPurpose").each(function(){
        myArray.push($(this).val())
    });

    $(".linkedServiceDonationPurpose").each(function(){
    for ( var i = 0; i < myArray.length; i = i + 1 ) {
        for ( var j = i+1; j < myArray.length; j = j + 1 )
            if(myArray[i] == myArray[j] &&  $(this).val() == myArray[j]){
                $(this).next( "div" ).html('Duplicate item selected');
                success=false;
           }
        } 
    });
    if (success) {
        return true;
    } else {
        return false;
    }
    function resetErrorMessages() {
        $(".error").each(function(){
            $(this).html('');
        });``
    }
}

Sum all values in every column of a data.frame in R

For the sake of completion:

 apply(people[,-1], 2, function(x) sum(x))
#Height Weight 
#   199    425 

CSS width of a <span> tag

You could explicitly set the display property to "block" so it behaves like a block level element, but in that case you should probably just use a div instead.

<span style="display:block; background-color:red; width:100px;"></span>

How can I do a BEFORE UPDATED trigger with sql server?

To do a BEFORE UPDATE in SQL Server I use a trick. I do a false update of the record (UPDATE Table SET Field = Field), in such way I get the previous image of the record.

Create an array of integers property in Objective-C

You can put this in your .h file for your class and define it as property, in XCode 7:

@property int  (*stuffILike) [10];

Advantage of switch over if-else statement

IMO this is a perfect example of what switch fall-through was made for.

How to modify existing XML file with XmlDocument and XmlNode in C#

You need to do something like this:

// instantiate XmlDocument and load XML from file
XmlDocument doc = new XmlDocument();
doc.Load(@"D:\test.xml");

// get a list of nodes - in this case, I'm selecting all <AID> nodes under
// the <GroupAIDs> node - change to suit your needs
XmlNodeList aNodes = doc.SelectNodes("/Equipment/DataCollections/GroupAIDs/AID");

// loop through all AID nodes
foreach (XmlNode aNode in aNodes)
{
   // grab the "id" attribute
   XmlAttribute idAttribute = aNode.Attributes["id"];

   // check if that attribute even exists...
   if (idAttribute != null)
   {
      // if yes - read its current value
      string currentValue = idAttribute.Value;

      // here, you can now decide what to do - for demo purposes,
      // I just set the ID value to a fixed value if it was empty before
      if (string.IsNullOrEmpty(currentValue))
      {
         idAttribute.Value = "515";
      }
   }
}

// save the XmlDocument back to disk
doc.Save(@"D:\test2.xml");

Get timezone from DateTime

No.

A developer is responsible for keeping track of time-zone information associated with a DateTime value via some external mechanism.

A quote from an excellent article here. A must read for every .Net developer.

So my advice is to write a little wrapper class that suits your needs.

Oracle: is there a tool to trace queries, like Profiler for sql server?

There is a commercial tool FlexTracer which can be used to trace Oracle SQL queries

Deserialize a JSON array in C#

[JsonProperty("name")]
public string name { get; set; }
[JsonProperty("Age")]
public int required { get; set; }
[JsonProperty("Location")]
public string type { get; set; }

and Remove a "{"..,

strFieldString = strFieldString.Remove(0, strFieldString.IndexOf('{'));

DeserializeObject..,

   optionsItem objActualField = JsonConvert.DeserializeObject<optionsItem(strFieldString);

how to toggle (hide/show) a table onClick of <a> tag in java script

Your anchor tag should be:

  <a id="loginLink" onclick="showHideTable();" href="#">Login</a>

And You javascript function :

function showHideTable()
{
   if (document.getElementById("loginTable").style.display == "none" ) {
       document.getElementById("loginTable").style.display="";

   } else {
      document.getElementById("loginTable").style.display="none";

}

function to remove duplicate characters in a string

public class RemoveDuplicateInString {
    public static void main(String[] args) {
        String s = "ABCDDCA";
        RemoveDuplicateInString rs = new RemoveDuplicateInString();
        System.out.println(rs.removeDuplicate(s));

    }

    public String removeDuplicate(String s) {
        String retn = null;
        boolean[] b = new boolean[256];

        char[] ch = s.toCharArray();
        for (int i = 0; i < ch.length; i++) {

            if (b[ch[i]]) {
                ch[i]=' ';

            }

            else {
                b[ch[i]] = true;

            }
        }

        retn = new String(ch);
        return retn;

    }

}

Is it possible in Java to check if objects fields are null and then add default value to all those attributes?

You can create a function that returns a boolean value and checks every attribute. You can call that function to do the job for you.

Alternatively, you can initialize the object with default values. That way there is no need for you to do any checking.

Linker Error C++ "undefined reference "

This error tells you everything:

undefined reference toHash::insert(int, char)

You're not linking with the implementations of functions defined in Hash.h. Don't you have a Hash.cpp to also compile and link?

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled

In my case i have included jdbc api dependencies in the project so the "Hello World" not printed. After removing the below dependency it works like a charm.

       <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>

Bootstrap 3 Collapse show state with Chevron icon

Here's a couple of pure css helper classes which lets you handle any kind of toggle content right in your html.

It works with any element you need to switch. Whatever your layout is you just put it inside a couple of elements with the .if-collapsed and .if-not-collapsed classes within the toggle element.

The only catch is that you have to make sure you put the desired initial state of the toggle. If it's initially closed, then put a collapsed class on the toggle.

It also requires the :not selector, it doesn't work on IE8.

HTML example:

<a class="btn btn-primary collapsed" data-toggle="collapse" href="#collapseExample">
  <!--You can put any valid html inside these!-->
  <span class="if-collapsed">Open</span>
  <span class="if-not-collapsed">Close</span>
</a>
<div class="collapse" id="collapseExample">
  <div class="well">
    ...
  </div>
</div>

Less version:

[data-toggle="collapse"] {
    &.collapsed .if-not-collapsed {
         display: none;
    }
    &:not(.collapsed) .if-collapsed {
         display: none;
    }
}

CSS version:

[data-toggle="collapse"].collapsed .if-not-collapsed {
  display: none;
}
[data-toggle="collapse"]:not(.collapsed) .if-collapsed {
  display: none;
}

How can I read a large text file line by line using Java?

Java 9:

try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
    stream.forEach(System.out::println);
}

How do I add a library project to Android Studio?

The easiest way I found to include external library project is (for example to include a Facebook library which is stored one directory up in the dependencies folder):

  1. In settings.gradle add

    include ':facebook'
    
    project(':facebook').projectDir = new File(settingsDir, '../dependencies/FacebookSDK')
    
  2. In build.gradle dependencies section, add

    compile project ('facebook')
    

All left to do is synchronise the project with gradle files.

Convert JSON to Map

I like google gson library.
When you don't know structure of json. You can use

JsonElement root = new JsonParser().parse(jsonString);

and then you can work with json. e.g. how to get "value1" from your gson:

String value1 = root.getAsJsonObject().get("data").getAsJsonObject().get("field1").getAsString();

PHP CURL DELETE request

My own class request with wsse authentication

class Request {

    protected $_url;
    protected $_username;
    protected $_apiKey;

    public function __construct($url, $username, $apiUserKey) {
        $this->_url = $url;     
        $this->_username = $username;
        $this->_apiKey = $apiUserKey;
    }

    public function getHeader() {
        $nonce = uniqid();
        $created = date('c');
        $digest = base64_encode(sha1(base64_decode($nonce) . $created . $this->_apiKey, true));

        $wsseHeader = "Authorization: WSSE profile=\"UsernameToken\"\n";
        $wsseHeader .= sprintf(
            'X-WSSE: UsernameToken Username="%s", PasswordDigest="%s", Nonce="%s", Created="%s"', $this->_username, $digest, $nonce, $created
        );

        return $wsseHeader;
    }

    public function curl_req($path, $verb=NULL, $data=array()) {                    

        $wsseHeader[] = "Accept: application/vnd.api+json";
        $wsseHeader[] = $this->getHeader();

        $options = array(
            CURLOPT_URL => $this->_url . $path,
            CURLOPT_HTTPHEADER => $wsseHeader,
            CURLOPT_RETURNTRANSFER => true, 
            CURLOPT_HEADER => false             
        );                  

        if( !empty($data) ) {
            $options += array(
                CURLOPT_POSTFIELDS => $data,
                CURLOPT_SAFE_UPLOAD => true
            );                          
        }

        if( isset($verb) ) {
            $options += array(CURLOPT_CUSTOMREQUEST => $verb);                          
        }

        $ch = curl_init();
        curl_setopt_array($ch, $options);
        $result = curl_exec($ch);                   

        if(false === $result ) {
            echo curl_error($ch);
        }
        curl_close($ch);

        return $result; 
    }
}

How to add anything in <head> through jquery/javascript?

Try a javascript pure:

Library JS:

appendHtml = function(element, html) {
    var div = document.createElement('div');
    div.innerHTML = html;
    while (div.children.length > 0) {
        element.appendChild(div.children[0]);
    }
}

Type: appendHtml(document.head, '<link rel="stylesheet" type="text/css" href="http://example.com/example.css"/>');

or jQuery:

$('head').append($('<link rel="stylesheet" type="text/css" />').attr('href', 'http://example.com/example.css'));

Format decimal for percentage values?

I have found the above answer to be the best solution, but I don't like the leading space before the percent sign. I have seen somewhat complicated solutions, but I just use this Replace addition to the answer above instead of using other rounding solutions.

String.Format("Value: {0:P2}.", 0.8526).Replace(" %","%") // formats as 85.26% (varies by culture)

Java: Array with loop

The Array has declared without intializing the values and if you want to insert values by itterating the loop this code will work.

Public Class Program
{

public static void main(String args[])

{
 //Array Intialization
 int my[] = new int[6];

 for(int i=0;i<=5;i++)

{

//Storing array values in array
my[i]= i;

//Printing array values

System.out.println(my[i]);

}

}

}

Python - add PYTHONPATH during command line module run

If you are running the command from a POSIX-compliant shell, like bash, you can set the environment variable like this:

PYTHONPATH="/path/to" python somescript.py somecommand

If it's all on one line, the PYTHONPATH environment value applies only to that one command.

$ echo $PYTHONPATH

$ python -c 'import sys;print("/tmp/pydir" in sys.path)'
False
$ PYTHONPATH=/tmp/pydir python -c 'import sys;print("/tmp/pydir" in sys.path)'
True
$ echo $PYTHONPATH

Java NIO: What does IOException: Broken pipe mean?

Broken pipe means you wrote to a connection that is already closed by the other end.

isConnected() does not detect this condition. Only a write does.

is it wise to always call SocketChannel.isConnected() before attempting a SocketChannel.write()

It is pointless. The socket itself is connected. You connected it. What may not be connected is the connection itself, and you can only determine that by trying it.

Best /Fastest way to read an Excel Sheet into a DataTable?

public DataTable ImportExceltoDatatable(string filepath)
{
    // string sqlquery= "Select * From [SheetName$] Where YourCondition";
    string sqlquery = "Select * From [SheetName$] Where Id='ID_007'";
    DataSet ds = new DataSet();
    string constring = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + filepath + ";Extended Properties=\"Excel 12.0;HDR=YES;\"";
    OleDbConnection con = new OleDbConnection(constring + "");
    OleDbDataAdapter da = new OleDbDataAdapter(sqlquery, con);
    da.Fill(ds);
    DataTable dt = ds.Tables[0];
    return dt;
}

Concatenating variables and strings in React

the best way to concat props/variables:

var sample = "test";    
var result = `this is just a ${sample}`;    
//this is just a test

Get 2 Digit Number For The Month

there are different ways of doing it

  • Using RTRIM and specifing the range:

like

SELECT RIGHT('0' + RTRIM(MONTH('12-31-2012')), 2); 
  • Using Substring to just extract the month part after converting the date into text

like

SELECT SUBSTRING(CONVERT(nvarchar(6),getdate(), 112),5,2)

see Fiddle

There may be other ways to get this.

MySQL compare DATE string with string from DATETIME field

SELECT * FROM `calendar` WHERE DATE(startTime) = '2010-04-29';

it helps , you can convert the values as DATE before comparing.

Java double.MAX_VALUE?

this states that Account.deposit(Double.MAX_VALUE); it is setting deposit value to MAX value of Double dataType.to procced for running tests.

Calculating the area under a curve given a set of coordinates, without knowing the function

The numpy and scipy libraries include the composite trapezoidal (numpy.trapz) and Simpson's (scipy.integrate.simps) rules.

Here's a simple example. In both trapz and simps, the argument dx=5 indicates that the spacing of the data along the x axis is 5 units.

from __future__ import print_function

import numpy as np
from scipy.integrate import simps
from numpy import trapz


# The y values.  A numpy array is used here,
# but a python list could also be used.
y = np.array([5, 20, 4, 18, 19, 18, 7, 4])

# Compute the area using the composite trapezoidal rule.
area = trapz(y, dx=5)
print("area =", area)

# Compute the area using the composite Simpson's rule.
area = simps(y, dx=5)
print("area =", area)

Output:

area = 452.5
area = 460.0

Add timestamp column with default NOW() for new rows only

You need to add the column with a default of null, then alter the column to have default now().

ALTER TABLE mytable ADD COLUMN created_at TIMESTAMP;
ALTER TABLE mytable ALTER COLUMN created_at SET DEFAULT now();

How to create global variables accessible in all views using Express / Node.JS?

In your app.js you need add something like this

global.myvar = 100;

Now, in all your files you want use this variable, you can just access it as myvar

How to convert a currency string to a double with jQuery or Javascript?

var parseCurrency = function (e) {
    if (typeof (e) === 'number') return e;
    if (typeof (e) === 'string') {
        var str = e.trim();
        var value = Number(e.replace(/[^0-9.-]+/g, ""));
        return str.startsWith('(') && str.endsWith(')') ? -value: value;
    }

    return e;
} 

What are good examples of genetic algorithms/genetic programming solutions?

I don't know if homework counts...

During my studies we rolled our own program to solve the Traveling Salesman problem.

The idea was to make a comparison on several criteria (difficulty to map the problem, performance, etc) and we also used other techniques such as Simulated annealing.

It worked pretty well, but it took us a while to understand how to do the 'reproduction' phase correctly: modeling the problem at hand into something suitable for Genetic programming really struck me as the hardest part...

It was an interesting course since we also dabbled with neural networks and the like.

I'd like to know if anyone used this kind of programming in 'production' code.

how to know status of currently running jobs

I found a better answer by Kenneth Fisher. The following query returns only currently running jobs:

SELECT
    ja.job_id,
    j.name AS job_name,
    ja.start_execution_date,      
    ISNULL(last_executed_step_id,0)+1 AS current_executed_step_id,
    Js.step_name
FROM msdb.dbo.sysjobactivity ja 
LEFT JOIN msdb.dbo.sysjobhistory jh ON ja.job_history_id = jh.instance_id
JOIN msdb.dbo.sysjobs j ON ja.job_id = j.job_id
JOIN msdb.dbo.sysjobsteps js
    ON ja.job_id = js.job_id
    AND ISNULL(ja.last_executed_step_id,0)+1 = js.step_id
WHERE
  ja.session_id = (
    SELECT TOP 1 session_id FROM msdb.dbo.syssessions ORDER BY agent_start_date DESC
  )
AND start_execution_date is not null
AND stop_execution_date is null;

You can get more information about a job by adding more columns from msdb.dbo.sysjobactivity table in select clause.

React Native add bold or italics to single words in <Text> field

You can also put a Text tag inside of another Text tag. The second text tag will inherit the styling of the first, but you maintain the ability to style it independently from its parent.

<Text style={styles.bold}>Level: 
    <Text style={styles.normal}>Easy</Text>
</Text>

//in your stylesheet...

  bold: {
    fontSize: 25,
    fontWeight: "bold",
    color: "blue",
  },
  normal: {
  // will inherit size and color attributes
    fontWeight: "normal",
  }

Check if a file exists or not in Windows PowerShell?

The standard way to see if a file exists is with the Test-Path cmdlet.

Test-Path -path $filename

bootstrap datepicker today as default

According to this link Set default date of jquery datepicker, the other solution is

var d = new Date();

var currDate = d.getDate();
var currMonth = d.getMonth();
var currYear = d.getFullYear();

var dateStr = currDate + "-" + currMonth + "-" + currYear;

$("#datepicker").datepicker(({dateFormat: "dd-mm-yy" autoclose: true, defaultDate: dateStr });

Sublime 3 - Set Key map for function Goto Definition

For anyone else who wants to set Eclipse style goto definition, you need to create .sublime-mousemap file in Sublime User folder.

Windows - create Default (Windows).sublime-mousemap in %appdata%\Sublime Text 3\Packages\User

Linux - create Default (Linux).sublime-mousemap in ~/.config/sublime-text-3/Packages/User

Mac - create Default (OSX).sublime-mousemap in ~/Library/Application Support/Sublime Text 3/Packages/User

Now open that file and put the following configuration inside

[
    {
        "button": "button1", 
        "count": 1, 
        "modifiers": ["ctrl"],
        "press_command": "drag_select",
        "command": "goto_definition"
    }
]

You can change modifiers key as you like.


Since Ctrl-button1 on Windows and Linux is used for multiple selections, adding a second modifier key like Alt might be a good idea if you want to use both features:

[
    {
        "button": "button1", 
        "count": 1, 
        "modifiers": ["ctrl", "alt"],
        "press_command": "drag_select",
        "command": "goto_definition"
    }
]

Alternatively, you could use the right mouse button (button2) with Ctrl alone, and not interfere with any built-in functions.

Android Imagebutton change Image OnClick

You can do it right in your XML file:

android:onClick="@drawable/ic_action_search"

Java Timer vs ExecutorService?

If it's available to you, then it's difficult to think of a reason not to use the Java 5 executor framework. Calling:

ScheduledExecutorService ex = Executors.newSingleThreadScheduledExecutor();

will give you a ScheduledExecutorService with similar functionality to Timer (i.e. it will be single-threaded) but whose access may be slightly more scalable (under the hood, it uses concurrent structures rather than complete synchronization as with the Timer class). Using a ScheduledExecutorService also gives you advantages such as:

  • You can customize it if need be (see the newScheduledThreadPoolExecutor() or the ScheduledThreadPoolExecutor class)
  • The 'one off' executions can return results

About the only reasons for sticking to Timer I can think of are:

  • It is available pre Java 5
  • A similar class is provided in J2ME, which could make porting your application easier (but it wouldn't be terribly difficult to add a common layer of abstraction in this case)

Make an HTTP request with android

Note: The Apache HTTP Client bundled with Android is now deprecated in favor of HttpURLConnection. Please see the Android Developers Blog for more details.

Add <uses-permission android:name="android.permission.INTERNET" /> to your manifest.

You would then retrieve a web page like so:

URL url = new URL("http://www.android.com/");
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
try {
     InputStream in = new BufferedInputStream(urlConnection.getInputStream());
     readStream(in);
}
finally {
     urlConnection.disconnect();
}

I also suggest running it on a separate thread:

class RequestTask extends AsyncTask<String, String, String>{

@Override
protected String doInBackground(String... uri) {
    String responseString = null;
    try {
        URL url = new URL(myurl);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        if(conn.getResponseCode() == HttpsURLConnection.HTTP_OK){
            // Do normal input or output stream reading
        }
        else {
            response = "FAILED"; // See documentation for more info on response handling
        }
    } catch (ClientProtocolException e) {
        //TODO Handle problems..
    } catch (IOException e) {
        //TODO Handle problems..
    }
    return responseString;
}

@Override
protected void onPostExecute(String result) {
    super.onPostExecute(result);
    //Do anything with response..
}
}

See the documentation for more information on response handling and POST requests.

Subtracting 2 lists in Python

arr1=[1,2,3]
arr2=[2,1,3]
ls=[arr2-arr1 for arr1,arr2 in zip(arr1,arr2)]
print(ls)
>>[1,-1,0]

Make file echo displaying "$PATH" string

The make uses the $ for its own variable expansions. E.g. single character variable $A or variable with a long name - ${VAR} and $(VAR).

To put the $ into a command, use the $$, for example:

all:
  @echo "Please execute next commands:"
  @echo 'setenv PATH /usr/local/greenhills/mips5/linux86:$$PATH'

Also note that to make the "" and '' (double and single quoting) do not play any role and they are passed verbatim to the shell. (Remove the @ sign to see what make sends to shell.) To prevent the shell from expanding $PATH, second line uses the ''.

How to get the list of properties of a class?

I am also facing this kind of requirement.

From this discussion I got another Idea,

Obj.GetType().GetProperties()[0].Name

This is also showing the property name.

Obj.GetType().GetProperties().Count();

this showing number of properties.

Thanks to all. This is nice discussion.

Connect Java to a MySQL database

Download JDBC Driver

Download link (Select platform independent): https://dev.mysql.com/downloads/connector/j/

Move JDBC Driver to C Drive

Unzip the files and move to C:\ drive. Your driver path should be like C:\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19

Run Your Java

java -cp "C:\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19\mysql-connector-java-8.0.19.jar" testMySQL.java

testMySQL.java

import java.sql.*;
import java.io.*;

public class testMySQL {
    public static void main(String[] args) {
    // TODO Auto-generated method stub
        try
        {  
            Class.forName("com.mysql.cj.jdbc.Driver");  
            Connection con=DriverManager.getConnection(  
                "jdbc:mysql://localhost:3306/db?useSSL=false&useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC","root","");  
            Statement stmt=con.createStatement();  
            ResultSet rs=stmt.executeQuery("show databases;");  
            System.out.println("Connected");  
        }
        catch(Exception e)
        {
            System.out.println(e);
        }

    }  

}

enter image description here

how to set "camera position" for 3d plots using python/matplotlib?

Minimal example varying azim, dist and elev

To add some simple sample images to what was explained at: https://stackoverflow.com/a/12905458/895245

Here is my test program:

#!/usr/bin/env python3

import sys

import matplotlib.pyplot as plt
from matplotlib import cm
from matplotlib.ticker import LinearLocator, FormatStrFormatter
import numpy as np

fig = plt.figure()
ax = fig.gca(projection='3d')

if len(sys.argv) > 1:
    azim = int(sys.argv[1])
else:
    azim = None
if len(sys.argv) > 2:
    dist = int(sys.argv[2])
else:
    dist = None
if len(sys.argv) > 3:
    elev = int(sys.argv[3])
else:
    elev = None

# Make data.
X = np.arange(-5, 6, 1)
Y = np.arange(-5, 6, 1)
X, Y = np.meshgrid(X, Y)
Z = X**2

# Plot the surface.
surf = ax.plot_surface(X, Y, Z, linewidth=0, antialiased=False)

# Labels.
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_zlabel('z')

if azim is not None:
    ax.azim = azim
if dist is not None:
    ax.dist = dist
if elev is not None:
    ax.elev = elev

print('ax.azim = {}'.format(ax.azim))
print('ax.dist = {}'.format(ax.dist))
print('ax.elev = {}'.format(ax.elev))

plt.savefig(
    'main_{}_{}_{}.png'.format(ax.azim, ax.dist, ax.elev),
    format='png',
    bbox_inches='tight'
)

Running it without arguments gives the default values:

ax.azim = -60
ax.dist = 10
ax.elev = 30

main_-60_10_30.png

enter image description here

Vary azim

The azimuth is the rotation around the z axis e.g.:

  • 0 means "looking from +x"
  • 90 means "looking from +y"

main_-60_10_30.png

enter image description here

main_0_10_30.png

enter image description here

main_60_10_30.png

enter image description here

Vary dist

dist seems to be the distance from the center visible point in data coordinates.

main_-60_10_30.png

enter image description here

main_-60_5_30.png

enter image description here

main_-60_20_-30.png

enter image description here

Vary elev

From this we understand that elev is the angle between the eye and the xy plane.

main_-60_10_60.png

enter image description here

main_-60_10_30.png

enter image description here

main_-60_10_0.png

enter image description here

main_-60_10_-30.png

enter image description here

Tested on matpotlib==3.2.2.

How do I ignore all files in a folder with a Git repository in Sourcetree?

  • Ignore all files in folder with Git in Sourcetree:

Ignore all files in folder with Git in Sourcetree

Apache Prefork vs Worker MPM

Apache's Multi-Processing Modules (MPMs) are responsible for binding to network ports on the machine, accepting requests, and dispatching children to handle the requests (http://httpd.apache.org/docs/2.2/mpm.html).

They're like any other Apache module, except that just one and only one MPM must be loaded into the server at any time. MPMs are chosen during configuration and compiled into the server by using the argument --with-mpm=NAME with the configure script where NAME is the name of the desired MPM.

Apache will use a default MPM for each operating system unless a different one is choosen at compile-time (for instance on Windows mpm_winnt is used by default). Here's the list of operating systems and their default MPMs:

  • BeOS beos
  • Netware mpm_netware
  • OS/2 mpmt_os2
  • Unix/Linux prefork (update for Apache version = 2.4: prefork, worker, or event, depending on platform capabilities)
  • Windows mpm_winnt

To check what modules are compiled into the server use the command-line option -l (here is the documentation). For instance on a Windows installation you might get something like:

> httpd -l
Compiled in modules:
  core.c
  mod_win32.c
  mpm_winnt.c
  http_core.c
  mod_so.c

As of version 2.2 this is the list of available core features and MPM modules:

  • core - Core Apache HTTP Server features that are always available
  • mpm_common - A collection of directives that are implemented by more than one multi-processing module (MPM)
  • beos - This Multi-Processing Module is optimized for BeOS.
  • event - An experimental variant of the standard worker MPM
  • mpm_netware Multi-Processing Module implementing an exclusively threaded web server optimized for Novell NetWare
  • mpmt_os2 Hybrid multi-process, multi-threaded MPM for OS/2
  • prefork Implements a non-threaded, pre-forking web server
  • mpm_winnt - This Multi-Processing Module is optimized for Windows NT.
  • worker - Multi-Processing Module implementing a hybrid multi-threaded multi-process web server

Now, to the difference between prefork and worker.

The prefork MPM

implements a non-threaded, pre-forking web server that handles requests in a manner similar to Apache 1.3. It is appropriate for sites that need to avoid threading for compatibility with non-thread-safe libraries. It is also the best MPM for isolating each request, so that a problem with a single request will not affect any other.

The worker MPM implements a hybrid multi-process multi-threaded server and gives better performance, hence it should be preferred unless one is using other modules that contain non-thread-safe libraries (see also this discussion or this on Serverfault).

How can I detect whether an iframe is loaded?

I imagine this like that:

<html>
<head>
<script>
var frame_loaded = 0;
function setFrameLoaded()
{
   frame_loaded = 1;
   alert("Iframe is loaded");
}
$('#click').click(function(){
   if(frame_loaded == 1)
    console.log('iframe loaded')
   } else {
    console.log('iframe not loaded')
   }
})
</script>
</head>
<button id='click'>click me</button>

<iframe id='MainPopupIframe' onload='setFrameLoaded();' src='http://...' />...</iframe>

How to create an executable .exe file from a .m file

If your code is more of a data analysis routine (vs. visualization / GUI), try GNU Octave. It's free and many of its functions are compatible with MATLAB. (Not 100% but maybe 99.5%.)

rsync copy over only certain types of files using include option

One more addition: if you need to sync files by its extensions in one dir only (without of recursion) you should use a construction like this:

rsync -auzv --include './' --include '*.ext' --exclude '*' /source/dir/ /destination/dir/

Pay your attention to the dot in the first --include. --no-r does not work in this construction.

EDIT:

Thanks to gbyte.co for the valuable comment!

Java using enum with switch statement

The part you're missing is converting from the integer to the type-safe enum. Java will not do it automatically. There's a couple of ways you can go about this:

  1. Use a list of static final ints rather than a type-safe enum and switch on the int value you receive (this is the pre-Java 5 approach)
  2. Switch on either a specified id value (as described by heneryville) or the ordinal value of the enum values; i.e. guideView.GUIDE_VIEW_SEVEN_DAY.ordinal()
  3. Determine the enum value represented by the int value and then switch on the enum value.

    enum GuideView {
        SEVEN_DAY,
        NOW_SHOWING,
        ALL_TIMESLOTS
    }
    
    // Working on the assumption that your int value is 
    // the ordinal value of the items in your enum
    public void onClick(DialogInterface dialog, int which) {
        // do your own bounds checking
        GuideView whichView = GuideView.values()[which];
        switch (whichView) {
            case SEVEN_DAY:
                ...
                break;
            case NOW_SHOWING:
                ...
                break;
        }
    }
    

    You may find it more helpful / less error prone to write a custom valueOf implementation that takes your integer values as an argument to resolve the appropriate enum value and lets you centralize your bounds checking.

How do you round to 1 decimal place in Javascript?

Using toPrecision method:

var a = 1.2345
a.toPrecision(2)

// result "1.2"

Mismatched anonymous define() module

I had this error because I included the requirejs file along with other librairies included directly in a script tag. Those librairies (like lodash) used a define function that was conflicting with require's define. The requirejs file was loading asynchronously so I suspect that the require's define was defined after the other libraries define, hence the conflict.

To get rid of the error, include all your other js files by using requirejs.

Escaping a forward slash in a regular expression

For java, you don't need to.

eg: "^(.*)/\\*LOG:(\\d+)\\*/(.*)$" ==> ^(.*)/\*LOG:(\d+)\*/(.*)$

If you put \ in front of /. IDE will tell you "Redundant Character Escape "\/" in ReGex"

How to click an element in Selenium WebDriver using JavaScript

const {Builder, By, Key, util} = require('selenium-webdriver')

// FUNÇÃO PARA PAUSA
function sleep(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}

async function example() {

    // chrome
    let driver = await new Builder().forBrowser("firefox").build()
    await driver.get('https://www.google.com.br')
    // await driver.findElement(By.name('q')).sendKeys('Selenium' ,Key.RETURN)

    await sleep(2000)

    await driver.findElement(By.name('q')).sendKeys('Selenium')

    await sleep(2000)

    // CLICAR
    driver.findElement(By.name('btnK')).click()


}
example()

Com essas últimas linhas, você pode clicar !

Cannot GET / Nodejs Error

I think you're missing your routes, you need to define at least one route for example '/' to index.

e.g.

app.get('/', function (req, res) {
  res.render('index', {});
});

validate a dropdownlist in asp.net mvc

There is an overload with 3 arguments. Html.DropdownList(name, selectList, optionLabel) Update: there was a typo in the below code snippet.

@Html.DropDownList("Cat", new SelectList(ViewBag.Categories,"ID", "CategoryName"), "-Select Category-")

For the validator use

@Html.ValidationMessage("Cat")

run program in Python shell

From the same folder, you can do:

import test

Javascript / Chrome - How to copy an object from the webkit inspector as code

Add this to your console and execute

copy(JSON.stringify(foo));

This copies your JSON to clipboard

How to create JSON post to api using C#

Have you tried using the WebClient class?

you should be able to use

string result = "";
using (var client = new WebClient())
{
    client.Headers[HttpRequestHeader.ContentType] = "application/json"; 
    result = client.UploadString(url, "POST", json);
}
Console.WriteLine(result);

Documentation at

http://msdn.microsoft.com/en-us/library/system.net.webclient%28v=vs.110%29.aspx

http://msdn.microsoft.com/en-us/library/d0d3595k%28v=vs.110%29.aspx

sendmail: how to configure sendmail on ubuntu?

When you typed in sudo sendmailconfig, you should have been prompted to configure sendmail.

For reference, the files that are updated during configuration are located at the following (in case you want to update them manually):

/etc/mail/sendmail.conf
/etc/cron.d/sendmail
/etc/mail/sendmail.mc

You can test sendmail to see if it is properly configured and setup by typing the following into the command line:

$ echo "My test email being sent from sendmail" | /usr/sbin/sendmail [email protected]

The following will allow you to add smtp relay to sendmail:

#Change to your mail config directory:
cd /etc/mail

#Make a auth subdirectory
mkdir auth
chmod 700 auth

#Create a file with your auth information to the smtp server
cd auth
touch client-info

#In the file, put the following, matching up to your smtp server:
AuthInfo:your.isp.net "U:root" "I:user" "P:password"

#Generate the Authentication database, make both files readable only by root
makemap hash client-info < client-info
chmod 600 client-info
cd ..

Add the following lines to sendmail.mc, but before the MAILERDEFINITIONS. Make sure you update your smtp server.

define(`SMART_HOST',`your.isp.net')dnl
define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
FEATURE(`authinfo',`hash -o /etc/mail/auth/client-info.db')dnl

Invoke creation sendmail.cf (alternatively run make -C /etc/mail):

m4 sendmail.mc > sendmail.cf

Restart the sendmail daemon:

service sendmail restart

String concatenation with Groovy

Reproducing tim_yates answer on current hardware and adding leftShift() and concat() method to check the finding:

  'String leftShift' {
    foo << bar << baz
  }
  'String concat' {
    foo.concat(bar)
       .concat(baz)
       .toString()
  }

The outcome shows concat() to be the faster solution for a pure String, but if you can handle GString somewhere else, GString template is still ahead, while honorable mention should go to leftShift() (bitwise operator) and StringBuffer() with initial allocation:

Environment
===========
* Groovy: 2.4.8
* JVM: OpenJDK 64-Bit Server VM (25.191-b12, Oracle Corporation)
    * JRE: 1.8.0_191
    * Total Memory: 238 MB
    * Maximum Memory: 3504 MB
* OS: Linux (4.19.13-300.fc29.x86_64, amd64)

Options
=======
* Warm Up: Auto (- 60 sec)
* CPU Time Measurement: On

                                    user  system  cpu  real

String adder                         453       7  460   469
String leftShift                     287       2  289   295
String concat                        169       1  170   173
GString template                      24       0   24    24
Readable GString template             32       0   32    32
GString template toString            400       0  400   406
Readable GString template toString   412       0  412   419
StringBuilder                        325       3  328   334
StringBuffer                         390       1  391   398
StringBuffer with Allocation         259       1  260   265

Greater than and less than in one statement

Simple utility method:

public static boolean isBetween(int value, int min, int max)
{
  return((value > min) && (value < max));
}

CSS to select/style first word

Same thing, with jQuery:

$('#links a').each(function(){
    var me = $(this);
    me.html( me.text().replace(/(^\w+)/,'<strong>$1</strong>') );
  });

or

$('#links a').each(function(){
    var me = $(this)
       , t = me.text().split(' ');
    me.html( '<strong>'+t.shift()+'</strong> '+t.join(' ') );
  });

(Via 'Wizzud' on the jQuery Mailing List)

How to resolve "could not execute statement; SQL [n/a]; constraint [numbering];"?

Hibernate tries to insert data that violate underlying database integrity contraints.

There's probably misconfiguration in hibernate persistent classes and/or mapping configuration (*.hbm.xml or annotations in persitent classes).

Maybe a property of the bean you want to save is not type-compatible with its related field in database (could explain the constraint [numbering] part).

how to display a div triggered by onclick event

If you have the ID of the div, try this:

  <input type='submit' onclick='$("#div_id").show()'>

Python 3.2 Unable to import urllib2 (ImportError: No module named urllib2)

In python 3 urllib2 was merged into urllib. See also another Stack Overflow question and the urllib PEP 3108.

To make Python 2 code work in Python 3:

try:
    import urllib.request as urllib2
except ImportError:
    import urllib2

TypeError: 'builtin_function_or_method' object is not subscriptable

Looks like you typed brackets instead of parenthesis by mistake.

Parsing boolean values with argparse

If you want to allow --feature and --no-feature at the same time (last one wins)

This allows users to make a shell alias with --feature, and overriding it with --no-feature.

Python 3.9 and above

parser.add_argument('--feature', default=True, action=argparse.BooleanOptionalAction)

Python 3.8 and below

I recommend mgilson's answer:

parser.add_argument('--feature', dest='feature', action='store_true')
parser.add_argument('--no-feature', dest='feature', action='store_false')
parser.set_defaults(feature=True)

If you DON'T want to allow --feature and --no-feature at the same time

You can use a mutually exclusive group:

feature_parser = parser.add_mutually_exclusive_group(required=False)
feature_parser.add_argument('--feature', dest='feature', action='store_true')
feature_parser.add_argument('--no-feature', dest='feature', action='store_false')
parser.set_defaults(feature=True)

You can use this helper if you are going to set many of them:

def add_bool_arg(parser, name, default=False):
    group = parser.add_mutually_exclusive_group(required=False)
    group.add_argument('--' + name, dest=name, action='store_true')
    group.add_argument('--no-' + name, dest=name, action='store_false')
    parser.set_defaults(**{name:default})

add_bool_arg(parser, 'useful-feature')
add_bool_arg(parser, 'even-more-useful-feature')

Firefox and SSL: sec_error_unknown_issuer

If anyone else is experiencing this issue with an Ubuntu LAMP and "COMODO Positive SSL" try to build your own bundle from the certs in the compressed file.

cat AddTrustExternalCARoot.crt COMODORSAAddTrustCA.crt COMODORSADomainValidationSecureServerCA.crt > YOURDOMAIN.ca-bundle

No mapping found for HTTP request with URI.... in DispatcherServlet with name

Removing the Tomcat Server and adding new tomcat configuration in Eclipse resolved issue for me.

Rotate an image in image source in html

You can do this:

<img src="your image" style="transform:rotate(90deg);">

it is much easier.

Is there a decent wait function in C++?

Well, this is an old post but I will just contribute to the question -- someone may find it useful later:

adding 'cin.get();' function just before the return of the main() seems to always stop the program from exiting before printing the results: see sample code below:

int main(){ string fname, lname;

  //ask user to enter name first and last name
  cout << "Please enter your first name: ";
  cin >> fname;

  cout << "Please enter your last name: ";
  cin >> lname;     
  cout << "\n\n\n\nyour first name is: " << fname << "\nyour last name is: " 
  << lname <<endl;

  //stop program from exiting before printing results on the screen
  cin.get();
  return 0;

}

What is ROWS UNBOUNDED PRECEDING used for in Teradata?

It's the "frame" or "range" clause of window functions, which are part of the SQL standard and implemented in many databases, including Teradata.

A simple example would be to calculate the average amount in a frame of three days. I'm using PostgreSQL syntax for the example, but it will be the same for Teradata:

WITH data (t, a) AS (
  VALUES(1, 1),
        (2, 5),
        (3, 3),
        (4, 5),
        (5, 4),
        (6, 11)
)
SELECT t, a, avg(a) OVER (ORDER BY t ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
FROM data
ORDER BY t

... which yields:

t  a  avg
----------
1  1  3.00
2  5  3.00
3  3  4.33
4  5  4.00
5  4  6.67
6 11  7.50

As you can see, each average is calculated "over" an ordered frame consisting of the range between the previous row (1 preceding) and the subsequent row (1 following).

When you write ROWS UNBOUNDED PRECEDING, then the frame's lower bound is simply infinite. This is useful when calculating sums (i.e. "running totals"), for instance:

WITH data (t, a) AS (
  VALUES(1, 1),
        (2, 5),
        (3, 3),
        (4, 5),
        (5, 4),
        (6, 11)
)
SELECT t, a, sum(a) OVER (ORDER BY t ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)
FROM data
ORDER BY t

yielding...

t  a  sum
---------
1  1    1
2  5    6
3  3    9
4  5   14
5  4   18
6 11   29

Here's another very good explanations of SQL window functions.

Git on Bitbucket: Always asked for password, even after uploading my public SSH key

If you still get too many authentication failures errors:

nano ~/.ssh/config

And paste:

Host bitbucket_james
    HostName bitbucket.org
    User james
    Port 22
    IdentitiesOnly=yes
    IdentityFile=~/.ssh/id_rsa_bitbucket_james

And most important - you should bitbucket_james alias instead of bitbucket.org when you set up your remote URL:

git remote set-url origin git@bitbucket_james:repo_owner_user/repo_name.git

Pass table as parameter into sql server UDF

You can, however no any table. From documentation:

For Transact-SQL functions, all data types, including CLR user-defined types and user-defined table types, are allowed except the timestamp data type.

You can use user-defined table types.

Example of user-defined table type:

CREATE TYPE TableType 
AS TABLE (LocationName VARCHAR(50))
GO 

DECLARE @myTable TableType
INSERT INTO @myTable(LocationName) VALUES('aaa')
SELECT * FROM @myTable

So what you can do is to define your table type, for example TableType and define the function which takes the parameter of this type. An example function:

CREATE FUNCTION Example( @TableName TableType READONLY)
RETURNS VARCHAR(50)
AS
BEGIN
    DECLARE @name VARCHAR(50)

    SELECT TOP 1 @name = LocationName FROM @TableName
    RETURN @name
END

The parameter has to be READONLY. And example usage:

DECLARE @myTable TableType
INSERT INTO @myTable(LocationName) VALUES('aaa')
SELECT * FROM @myTable

SELECT dbo.Example(@myTable)

Depending on what you want achieve you can modify this code.

EDIT: If you have a data in a table you may create a variable:

DECLARE @myTable TableType

And take data from your table to the variable

INSERT INTO @myTable(field_name)
SELECT field_name_2 FROM my_other_table

How to remove a key from Hash and get the remaining hash in Ruby/Rails?

Hash#except (Ruby 3.0+)

Starting from Ruby 3.0, Hash#except is a build-in method.

As a result, there is no more need to depend on ActiveSupport or write monkey-patches in order to use it.

h = { a: 1, b: 2, c: 3 }
p h.except(:a) #=> {:b=>2, :c=>3}

Sources:

Is there a "null coalescing" operator in JavaScript?

function coalesce() {
    var len = arguments.length;
    for (var i=0; i<len; i++) {
        if (arguments[i] !== null && arguments[i] !== undefined) {
            return arguments[i];
        }
    }
    return null;
}

var xyz = {};
xyz.val = coalesce(null, undefined, xyz.val, 5);

// xyz.val now contains 5

this solution works like the SQL coalesce function, it accepts any number of arguments, and returns null if none of them have a value. It behaves like the C# ?? operator in the sense that "", false, and 0 are considered NOT NULL and therefore count as actual values. If you come from a .net background, this will be the most natural feeling solution.

Easy way to build Android UI?

The easiest way is with REBOL 3:

http://rebolforum.com/index.cgi?f=printtopic&permalink=Nick25-Aug-2013/10:08:38-7:00&archiveflag=new

Here are 10 fully functional demo programs, with GUIs. These run on Android and desktop OSs, using the exact same code:

REBOL []
load-gui
view [text "Hello World!"]


REBOL [title: "Tiny Note Editor"]
do %r3-gui.r3  ; download this file manually or just use load-gui as above
view [
    a1: area
    button "Save" on-action [write %notes.txt get-face a1]
    button "Load" on-action [set-face a1 to-string read %notes.txt]
]


REBOL [title: "Data Entry to CSV File"]
do %r3-gui.r3
view [
    text "First Name:"
    f1: field
    text "Last Name:"
    f2: field
    button "Submit" on-action [
        write/append %cntcts.txt rejoin [
            mold get-face f1 " " mold get-face f2 newline
        ]
        request "" "Saved"
    ]
    a1: area
    button "Load" on-action [set-face a1 to-string read %cntcts.txt]
]


REBOL [title: "Text File Reader (How to use a text list file selector)"]
do %r3-gui.r3
view [
    a1: area
    button "Load" on-action [
        files: read %./
        view/modal [
            text "File Name:"
            t2: text-list files on-action [
                set-face a1 to-string read(to-file pick files get-face t2)
                unview
            ]
        ]
    ]
]


REBOL [title: "List-View (Grid) Example"]
do %r3-gui.r3
view [
    text-table ["1" 200 "2" 100 "3"][
        ["asdf" "a" "4"]
        ["sdfg" "b" "3"]
        ["dfgh" "c" "2"]
        ["fghj" "d" "1"]
    ] 
]


REBOL [title: "Calculator"]
do %r3-gui.r3
stylize [
    btn: button [
        facets: [init-size: 50x50]
        actors: [on-action:[set-face f join get-face f get-face face]]
    ]
]
view [
    hgroup [
        f: field return
        btn "1"  btn "2"  btn "3"  btn " + "  return
        btn "4"  btn "5"  btn "6"  btn " - "  return
        btn "7"  btn "8"  btn "9"  btn " * "  return
        btn "0"  btn "."  btn " / "   btn "=" on-action [
            attempt [set-face f form do get-face f]
        ]
    ]
]


REBOL [title: "Sliding Tile Puzzle"]
do %r3-gui.r3
stylize [
    p: button [
        facets: [init-size: 60x60  max-size: 60x60]
        actors: [
            on-action: [
                t: face/gob/offset
                face/gob/offset: x/gob/offset
                x/gob/offset: t
            ]
        ]
    ]
]
view/options [
    hgroup [ 
        p "8"   p "7"   p "6"   return
        p "5"   p "4"   p "3"   return
        p "2"   p "1"   x: box 60x60 white
    ]
] [bg-color: white]


REBOL [title: "Math Test"]
do %r3-gui.r3
random/seed now
x: does [rejoin [random 10 " + " random 20]]
view [
    f1: field (x)
    text "Answer:"
    f2: field on-action [
        either (get-face f2) = (form do get-face f1) [
            request "Yes!" "Yes!"][request "No!" "No!"
        ]
        set-face f1 x
        set-face f2 ""
        focus f2
    ]
]


REBOL [title: "Minimal Cash Register"]
do %r3-gui.r3
stylize [fld: field [init-size: 80]]   
view [
    hgroup [
        text "Cashier:"   cashier: fld 
        text "Item:"      item: fld 
        text "Price:"     price: fld on-action [
            if error? try [to-money get-face price] [
                request "Error" "Price error" 
                return none
            ]
            set-face a rejoin [
                get-face a mold get-face item tab get-face price newline
            ]
            set-face item copy "" set-face price copy ""
            sum: 0
            foreach [item price] load get-face a [
                sum: sum + to-money price
            ]
            set-face subtotal form sum
            set-face tax form sum * .06
            set-face total form sum * 1.06 
            focus item
        ]
        return
        a: area 600x300
        return
        text "Subtotal:"   subtotal: fld 
        text "Tax:"        tax: fld 
        text "Total:"      total: fld
        button "Save" on-action [
            items: replace/all (mold load get-face a) newline " "
            write/append %sales.txt rejoin [
                items newline get-face cashier newline now/date newline
            ]
            set-face item copy "" set-face price copy "" 
            set-face a copy ""    set-face subtotal copy ""
            set-face tax copy "" set-face total copy ""
        ]
    ]
]


REBOL [title: "Requestors"]
do %r3-gui.r3
x: request/ask "Question" "Do you like this?."
either x = false [print "No!"] [print "Yes!"]
x: request/custom "" "Do you like this?" ["Yay" "Boo"]
either x = false [print "Boo!"] [print "Yay!"]
view [button "Click me" on-action[request "Ok" "You clicked the button."]]

List of Java processes

To know the list of java running on the linux machine. ps -e | grep java

Utility of HTTP header "Content-Type: application/force-download" for mobile?

Content-Type: application/force-download means "I, the web server, am going to lie to you (the browser) about what this file is so that you will not treat it as a PDF/Word Document/MP3/whatever and prompt the user to save the mysterious file to disk instead". It is a dirty hack that breaks horribly when the client doesn't do "save to disk".

Use the correct mime type for whatever media you are using (e.g. audio/mpeg for mp3).

Use the Content-Disposition: attachment; etc etc header if you want to encourage the client to download it instead of following the default behaviour.

How to select last one week data from today's date

  1. The query is correct

2A. As far as last seven days have much less rows than whole table an index can help

2B. If you are interested only in Created_Date you can try using some group by and count, it should help with the result set size

What port is used by Java RMI connection?

With reference to other answers above, here is my view -

there are ports involved on both client and server side.

  • for server/remote side, if you export the object without providing a port , remote object would use a random port to listen.

  • a client, when looks up the remote object, it would always use a random port on its side and will connect to the remote object port as listed above.

What does the term "Tuple" Mean in Relational Databases?

A tuple is used to define a slice of data from a cube; it is composed of an ordered collection of one member from one or more dimensions. A tuple is used to identify specific sections of multidimensional data from a cube; a tuple composed of one member from each dimension in a cube completely describes a cell value.

How to make a Java Generic method static?

the only thing you can do is to change your signature to

public static <E> E[] appendToArray(E[] array, E item)

Important details:

Generic expressions preceding the return value always introduce (declare) a new generic type variable.

Additionally, type variables between types (ArrayUtils) and static methods (appendToArray) never interfere with each other.

So, what does this mean: In my answer <E> would hide the E from ArrayUtils<E> if the method wouldn't be static. AND <E> has nothing to do with the E from ArrayUtils<E>.

To reflect this fact better, a more correct answer would be:

public static <I> I[] appendToArray(I[] array, I item)

What is the difference between Sprint and Iteration in Scrum and length of each Sprint?

"___ is largely an organizational issue caused by long hours, little down time, and continual peer, customer, and superior surveillance"

No this is not the definition of scrum, it is the wikipedia excerpt on the definition of burnout.

Dont do too many short 10 days sprints. You will burnout your team eventually. Use short sprints where you really need them, and don't do too many in a row. Think long-term. A distance runner always paces themselves for the full race and does sprints in short distances only where it matters.

If you burnout your team you can toss out all them fancy scrum charts, they won't do a thing for your team's plummeting productivity.

Submit form without reloading page

You can use jQuery serialize function along with get/post as follows:

$.get('server.php?' + $('#theForm').serialize())

$.post('server.php', $('#theform').serialize())

jQuery Serialize Documentation: http://api.jquery.com/serialize/

Simple AJAX submit using jQuery:

// this is the id of the submit button
$("#submitButtonId").click(function() {

    var url = "path/to/your/script.php"; // the script where you handle the form input.

    $.ajax({
           type: "POST",
           url: url,
           data: $("#idForm").serialize(), // serializes the form's elements.
           success: function(data)
           {
               alert(data); // show response from the php script.
           }
         });

    return false; // avoid to execute the actual submit of the form.
});

Execute JavaScript using Selenium WebDriver in C#

The shortest code

ChromeDriver drv = new ChromeDriver();

drv.Navigate().GoToUrl("https://stackoverflow.com/questions/6229769/execute-javascript-using-selenium-webdriver-in-c-sharp");

drv.ExecuteScript("return alert(document.title);");


git diff between two different files

Specify the paths explicitly:

git diff HEAD:full/path/to/foo full/path/to/bar

Check out the --find-renames option in the git-diff docs.

Credit: twaggs.

programmatically add column & rows to WPF Datagrid

To Bind the DataTable into the DataGridTextColumn in CodeBehind xaml

<DataGrid
  Name="TrkDataGrid"
  AutoGenerateColumns="False"
  ItemsSource="{Binding}">
</DataGrid>

xaml.cs

  foreach (DataColumn col in dt.Columns)
  {
    TrkDataGrid.Columns.Add(
      new DataGridTextColumn
      {
        Header = col.ColumnName,
        Binding = new Binding(string.Format("[{0}]", col.ColumnName))
      });
  }

  TrkDataGrid.ItemsSource= dt.DefaultView;

GridView VS GridLayout in Android Apps

A GridView is a ViewGroup that displays items in two-dimensional scrolling grid. The items in the grid come from the ListAdapter associated with this view.

This is what you'd want to use (keep using). Because a GridView gets its data from a ListAdapter, the only data loaded in memory will be the one displayed on screen. GridViews, much like ListViews reuse and recycle their views for better performance.

Whereas a GridLayout is a layout that places its children in a rectangular grid.

It was introduced in API level 14, and was recently backported in the Support Library. Its main purpose is to solve alignment and performance problems in other layouts. Check out this tutorial if you want to learn more about GridLayout.

How do I align a label and a textarea?

  1. Set the height of your label to the same height as the multiline textbox.
  2. Add the cssClass .alignTop{vertical-align: middle;} for the label control.

    <p>
        <asp:Label ID="DescriptionLabel" runat="server" Text="Description: " Width="70px" Height="200px" CssClass="alignTop"></asp:Label>
        <asp:Textbox id="DescriptionTextbox" runat="server" Width="400px" Height="200px" TextMode="MultiLine"></asp:Textbox>
        <asp:RequiredFieldValidator id="DescriptionRequiredFieldValidator" runat="server" ForeColor="Red"
        ControlToValidate="DescriptionTextbox" ErrorMessage="Description is a required field.">    
    </asp:RequiredFieldValidator>
    

iptables block access to port 8000 except from IP address

This question should be on Server Fault. Nevertheless, the following should do the trick, assuming you're talking about TCP and the IP you want to allow is 1.2.3.4:

iptables -A INPUT -p tcp --dport 8000 -s 1.2.3.4 -j ACCEPT
iptables -A INPUT -p tcp --dport 8000 -j DROP

How to use relative/absolute paths in css URLs?

i had the same problem... every time that i wanted to publish my css.. I had to make a search/replace.. and relative path wouldnt work either for me because the relative paths were different from dev to production.

Finally was tired of doing the search/replace and I created a dynamic css, (e.g. www.mysite.com/css.php) it's the same but now i could use my php constants in the css. somethig like

.icon{
  background-image:url('<?php echo BASE_IMAGE;?>icon.png');
}

and it's not a bad idea to make it dynamic because now i could compress it using YUI compressor without loosing the original format on my dev server.

Good Luck!

How to use opencv in using Gradle?

As per OpenCV docs(1), below steps using OpenCV manager is the recommended way to use OpenCV for production runs. But, OpenCV manager(2) is an additional install from Google play store. So, if you prefer a self contained apk(not using OpenCV manager) or is currently in development/testing phase, I suggest answer at https://stackoverflow.com/a/27421494/1180117.

Recommended steps for using OpenCV in Android Studio with OpenCV manager.

  1. Unzip OpenCV Android sdk downloaded from OpenCV.org(3)
  2. From File -> Import Module, choose sdk/java folder in the unzipped opencv archive.
  3. Update build.gradle under imported OpenCV module to update 4 fields to match your project's build.gradle a) compileSdkVersion b) buildToolsVersion c) minSdkVersion and 4) targetSdkVersion.
  4. Add module dependency by Application -> Module Settings, and select the Dependencies tab. Click + icon at bottom(or right), choose Module Dependency and select the imported OpenCV module.

As the final step, in your Activity class, add snippet below.

    public class SampleJava extends Activity  {

        private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) {
        @Override
        public void onManagerConnected(int status) {
            switch(status) {
                case LoaderCallbackInterface.SUCCESS:
                    Log.i(TAG,"OpenCV Manager Connected");
                    //from now onwards, you can use OpenCV API
                    Mat m = new Mat(5, 10, CvType.CV_8UC1, new Scalar(0));
                    break;
                case LoaderCallbackInterface.INIT_FAILED:
                    Log.i(TAG,"Init Failed");
                    break;
                case LoaderCallbackInterface.INSTALL_CANCELED:
                    Log.i(TAG,"Install Cancelled");
                    break;
                case LoaderCallbackInterface.INCOMPATIBLE_MANAGER_VERSION:
                    Log.i(TAG,"Incompatible Version");
                    break;
                case LoaderCallbackInterface.MARKET_ERROR:
                    Log.i(TAG,"Market Error");
                    break;
                default:
                    Log.i(TAG,"OpenCV Manager Install");
                    super.onManagerConnected(status);
                    break;
            }
        }
    };

    @Override
    protected void onResume() {
        super.onResume();
        //initialize OpenCV manager
        OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_2_4_9, this, mLoaderCallback);
    }
}

Note: You could only make OpenCV calls after you receive success callback on onManagerConnected method. During run, you will be prompted for installation of OpenCV manager from play store, if it is not already installed. During development, if you don't have access to play store or is on emualtor, use appropriate OpenCV manager apk present in apk folder under downloaded OpenCV sdk archive .

Pros

  • Apk size reduction by around 40 MB ( consider upgrades too ).
  • OpenCV manager installs optimized binaries for your hardware which could help speed.
  • Upgrades to OpenCV manager might save your app from bugs in OpenCV.
  • Different apps could share same OpenCV library.

Cons

  • End user experience - might not like a install prompt from with your application.

jQuery - Dynamically Create Button and Attach Event Handler

You were just adding the html string. Not the element you created with a click event listener.

Try This:

<html>
<head>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js"></script>
</head>
<body>
    <table id="addNodeTable">
        <tr>
            <td>
                Row 1
            </td>
        </tr>
        <tr >
            <td>
                Row 2
            </td>
        </tr>
    </table>
</body>
</html>
<script type="text/javascript">
    $(document).ready(function() {
        var test = $('<button>Test</button>').click(function () {
            alert('hi');
        });
        $("#addNodeTable tr:last").append('<tr><td></td></tr>').find("td:last").append(test);

    });
</script>

Apache POI Excel - how to configure columns to be expanded?

Tip : To make Auto size work , the call to sheet.autoSizeColumn(columnNumber) should be made after populating the data into the excel.

Calling the method before populating the data, will have no effect.

Difference between & and && in Java?

& is bitwise AND operator comparing bits of each operand.
For example,

int a = 4;
int b = 7;
System.out.println(a & b); // prints 4
//meaning in an 32 bit system
// 00000000 00000000 00000000 00000100
// 00000000 00000000 00000000 00000111
// ===================================
// 00000000 00000000 00000000 00000100


&& is logical AND operator comparing boolean values of operands only. It takes two operands indicating a boolean value and makes a lazy evaluation on them.

Why use #ifndef CLASS_H and #define CLASS_H in .h file but not in .cpp?

It is generally expected that modules of code such as .cpp files are compiled once and linked to in multiple projects, to avoid unnecessary repetitive compilation of logic. For example, g++ -o class.cpp would produce class.o which you could then link from multiple projects to using g++ main.cpp class.o.

We could use #include as our linker, as you seem to be implying, but that would just be silly when we know how to link properly using our compiler with less keystrokes and less wasteful repetition of compilation, rather than our code with more keystrokes and more wasteful repetition of compilation...

The header files are still required to be included into each of the multiple projects, however, because this provides the interface for each module. Without these headers the compiler wouldn't know about any of the symbols introduced by the .o files.

It is important to realise that the header files are what introduce the definitions of symbols for those modules; once that is realised then it makes sense that multiple inclusions could cause redefinitions of symbols (which causes errors), so we use include guards to prevent such redefinitions.

The import org.junit cannot be resolved

When you add TestNG to your Maven dependencies , Change scope from test to compile.Hope this would solve your issue..

How to export and import environment variables in windows?

I would use the SET command from the command prompt to export all the variables, rather than just PATH as recommended above.

C:\> SET >> allvariables.txt

To import the variablies, one can use a simple loop:

C:\> for /F %A in (allvariables.txt) do SET %A

Android center view in FrameLayout doesn't work

To center a view in Framelayout, there are some available tricks. The simplest one I used for my Webview and Progressbar(very similar to your two object layout), I just added android:layout_gravity="center"

Here is complete XML in case if someone else needs the same thing to do

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".WebviewPDFActivity"
    android:layout_gravity="center"
    >
    <WebView
        android:id="@+id/webView1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"

        />
    <ProgressBar
        android:id="@+id/progress_circular"
        android:layout_width="250dp"
        android:layout_height="250dp"
        android:visibility="visible"
        android:layout_gravity="center"
        />


</FrameLayout>

Here is my output

screenshot

Identify duplicates in a List

I took Sebastian's answer and added a keyExtractor to it -

    private <U, T> Set<T> findDuplicates(Collection<T> collection, Function<? super T,? extends U> keyExtractor) {
        Map<U, T> uniques = new HashMap<>(); // maps unique keys to corresponding values
        return collection.stream()
            .filter(e -> uniques.put(keyExtractor.apply(e), e) != null)
            .collect(Collectors.toSet());
    }

How do I remove the top margin in a web page?

The same issue has been driving me crazy for several hours. What I found and you may want to check is html encoding. In my html file I declared utf-8 encoding and used Notepad++ to enter html code in utf-8 format. What I DID forget of was UTF-8 BOM and No BOM difference. It seems when utf-8 declared html file is written as UTF-8 BOM there is some invisible extra character at the begining of the file. The character (non-printable I guess) effects in one row of "text" at the top of the rendered page. And you cannot see the difference in source-view of the browser (Chrome in my case). Both nice and spoiled files seem identical to the very character, still one of them renders nicely and the other one shows this freaking upper margin.

To wrap it up the solution is to convert the file to UTF-8 NO BOM and one can do it in i.e. Notepad++.

Android Min SDK Version vs. Target SDK Version

android:minSdkVersion and android:targetSdkVersion both are Integer value we need to declare in android manifest file but both are having different properties.

android:minSdkVersion: This is minimum required API level to run an android app. If we will install the same app on lower API version the parser error will be appear, and application not support problem will appear.

android:targetSdkVersion: Target sdk version is to set the Target API level of app. if this attribute not declared in manifest, minSdk version will be your TargetSdk Version. This is always true that "app support installation on all higher version of API we declared as TargetSdk Version". To make app limited target we need to declare maxSdkVersion in our manifest file...

Android Studio not showing modules in project structure

Please go to Module settings and choose Modules from Project Settings then you need to Select src and gen folders and marked them as Source folders by right-click on them and select Source

How to use "not" in xpath?

None of these answers worked for me for python. I solved by this

a[not(@id='XX')]

Also you can use or condition in your xpath by | operator. Such as

a[not(@id='XX')]|a[not(@class='YY')]

Sometimes we want element which has no class. So you can do like

a[not(@class)]

Using 24 hour time in bootstrap timepicker

<input type="text" name="time" data-provide="timepicker"  id="time" class="form-control" placeholder="Start Time" value="" />


$('#time').timepicker({
        timeFormat: 'H:i',
        'scrollDefaultNow'      : 'true',
        'closeOnWindowScroll'   : 'true',
        'showDuration'          : false,
        'ignoreReadonly'        : true,

})

work for me.

How to change package name of an Android Application

In Android Studio, which, quite honestly, you should be using, change the package name by right-clicking on the package name in the project structure -> Refactor -> Rename...

It then gives the option of renaming the directory or the package. Select the package. The directory should follow suit. Type in your new package name, and click Refactor. It will change all the imports and remove redundant imports for you. You can even have it fix it for you in comments and strings, etc.

Lastly, change the package name accordingly in your AndroidManifest.xml towards the top. Otherwise you will get errors everywhere complaining about R.whatever.

Another very useful solution

First create a new package with the desired nameby right clicking on thejava folder -> new -> package.`

Then, select and drag all your classes to the new package. AndroidStudio will re-factor the package name everywhere.

After that: in your app's build.gradle add/edit applicationId with the new one. i.e. (com.a.bc in my case):

defaultConfig {
    applicationId "com.a.bc"
    minSdkVersion 13
    targetSdkVersion 19
}

Original post and more comments here

Python: split a list based on a condition?

Concise and Elegant

Inspired by DanSalmo's comment, here is a solution that is concise, elegant, and at the same time is one of the fastest solutions.

good, bad = [], []
for item in my_list:
    good.append(item) if item in set(goodvals) else bad.append(item)

Tip: Turning goodval into a set gives us an easy 40% speed boost.

Fastest

If you have the need for maximum speed, we take the fastest answer and turbocharge it by turning good_list into a set. That gives us a 45% speed boost, and we end up with a solution that is more than 5.5x as fast as the slowest solution, even while it remains readable.

good_list_set = set(good_list)  # 45% faster than a tuple.

good, bad = [], []
for item in my_origin_list:
    if item in good_list_set:
        good.append(item)
    else:
        bad.append(item)

A little shorter:

good_list_set = set(good_list)  # 45% faster than a tuple.

good, bad = [], []
for item in my_origin_list:
    out = good if item in good_list_set else bad
    out.append(item)

Elegance can be somewhat subjective, but some of the Rube Goldberg style solutions that are cute and ingenious are quite concerning and should not be used in production code in any language, let alone python which is elegant at heart.

Benchmark results:

filter_BJHomer                  80/s       --   -3265%   -5312%   -5900%   -6262%   -7273%   -7363%   -8051%   -8162%   -8244%
zip_Funky                       118/s    4848%       --   -3040%   -3913%   -4450%   -5951%   -6085%   -7106%   -7271%   -7393%
two_lst_tuple_JohnLaRoy         170/s   11332%    4367%       --   -1254%   -2026%   -4182%   -4375%   -5842%   -6079%   -6254%
if_else_DBR                     195/s   14392%    6428%    1434%       --    -882%   -3348%   -3568%   -5246%   -5516%   -5717%
two_lst_compr_Parand            213/s   16750%    8016%    2540%     967%       --   -2705%   -2946%   -4786%   -5083%   -5303%
if_else_1_line_DanSalmo         292/s   26668%   14696%    7189%    5033%    3707%       --    -331%   -2853%   -3260%   -3562%
tuple_if_else                   302/s   27923%   15542%    7778%    5548%    4177%     343%       --   -2609%   -3029%   -3341%
set_1_line                      409/s   41308%   24556%   14053%   11035%    9181%    3993%    3529%       --    -569%    -991%
set_shorter                     434/s   44401%   26640%   15503%   12303%   10337%    4836%    4345%     603%       --    -448%
set_if_else                     454/s   46952%   28358%   16699%   13349%   11290%    5532%    5018%    1100%     469%       --

The full benchmark code for Python 3.7 (modified from FunkySayu):

good_list = ['.jpg','.jpeg','.gif','.bmp','.png']

import random
import string
my_origin_list = []
for i in range(10000):
    fname = ''.join(random.choice(string.ascii_lowercase) for i in range(random.randrange(10)))
    if random.getrandbits(1):
        fext = random.choice(list(good_list))
    else:
        fext = "." + ''.join(random.choice(string.ascii_lowercase) for i in range(3))

    my_origin_list.append((fname + fext, random.randrange(1000), fext))

# Parand
def two_lst_compr_Parand(*_):
    return [e for e in my_origin_list if e[2] in good_list], [e for e in my_origin_list if not e[2] in good_list]

# dbr
def if_else_DBR(*_):
    a, b = list(), list()
    for e in my_origin_list:
        if e[2] in good_list:
            a.append(e)
        else:
            b.append(e)
    return a, b

# John La Rooy
def two_lst_tuple_JohnLaRoy(*_):
    a, b = list(), list()
    for e in my_origin_list:
        (b, a)[e[2] in good_list].append(e)
    return a, b

# # Ants Aasma
# def f4():
#     l1, l2 = tee((e[2] in good_list, e) for e in my_origin_list)
#     return [i for p, i in l1 if p], [i for p, i in l2 if not p]

# My personal way to do
def zip_Funky(*_):
    a, b = zip(*[(e, None) if e[2] in good_list else (None, e) for e in my_origin_list])
    return list(filter(None, a)), list(filter(None, b))

# BJ Homer
def filter_BJHomer(*_):
    return list(filter(lambda e: e[2] in good_list, my_origin_list)), list(filter(lambda e: not e[2] in good_list,                                                                             my_origin_list))

# ChaimG's answer; as a list.
def if_else_1_line_DanSalmo(*_):
    good, bad = [], []
    for e in my_origin_list:
        _ = good.append(e) if e[2] in good_list else bad.append(e)
    return good, bad

# ChaimG's answer; as a set.
def set_1_line(*_):
    good_list_set = set(good_list)
    good, bad = [], []
    for e in my_origin_list:
        _ = good.append(e) if e[2] in good_list_set else bad.append(e)
    return good, bad

# ChaimG set and if else list.
def set_shorter(*_):
    good_list_set = set(good_list)
    good, bad = [], []
    for e in my_origin_list:
        out = good if e[2] in good_list_set else bad
        out.append(e)
    return good, bad

# ChaimG's best answer; if else as a set.
def set_if_else(*_):
    good_list_set = set(good_list)
    good, bad = [], []
    for e in my_origin_list:
        if e[2] in good_list_set:
            good.append(e)
        else:
            bad.append(e)
    return good, bad

# ChaimG's best answer; if else as a set.
def tuple_if_else(*_):
    good_list_tuple = tuple(good_list)
    good, bad = [], []
    for e in my_origin_list:
        if e[2] in good_list_tuple:
            good.append(e)
        else:
            bad.append(e)
    return good, bad

def cmpthese(n=0, functions=None):
    results = {}
    for func_name in functions:
        args = ['%s(range(256))' % func_name, 'from __main__ import %s' % func_name]
        t = Timer(*args)
        results[func_name] = 1 / (t.timeit(number=n) / n) # passes/sec

    functions_sorted = sorted(functions, key=results.__getitem__)
    for f in functions_sorted:
        diff = []
        for func in functions_sorted:
            if func == f:
                diff.append("--")
            else:
                diff.append(f"{results[f]/results[func]*100 - 100:5.0%}")
        diffs = " ".join(f'{x:>8s}' for x in diff)

        print(f"{f:27s} \t{results[f]:,.0f}/s {diffs}")


if __name__=='__main__':
    from timeit import Timer
cmpthese(1000, 'two_lst_compr_Parand if_else_DBR two_lst_tuple_JohnLaRoy zip_Funky filter_BJHomer if_else_1_line_DanSalmo set_1_line set_if_else tuple_if_else set_shorter'.split(" "))

How do you clear your Visual Studio cache on Windows Vista?

The accepted answer gave two locations:

here

C:\Documents and Settings\Administrator\Local Settings\Temp\VWDWebCache

and possibly here

C:\Documents and Settings\Administrator\Local Settings\Application Data\Microsoft\WebsiteCache

Did you try those?

Edited to add

On my Windows Vista machine, it's located in

%Temp%\VWDWebCache

and in

%LocalAppData%\Microsoft\WebsiteCache

From your additional information (regarding team edition) this comes from Clear Client TFS Cache:

Clear Client TFS Cache

Visual Studio and Team Explorer provide a caching mechanism which can get out of sync. If I have multiple instances of a single TFS which can be connected to from a single Visual Studio client, that client can become confused.

To solve it..

For Windows Vista delete contents of this folder

%LocalAppData%\Microsoft\Team Foundation\1.0\Cache

How do I extract data from JSON with PHP?

// Using json as php array 

$json = '[{"user_id":"1","user_name":"Sayeed Amin","time":"2019-11-06 13:21:26"}]';

//or use from file
//$json = file_get_contents('results.json');

$someArray = json_decode($json, true);

foreach ($someArray as $key => $value) {
    echo $value["user_id"] . ", " . $value["user_name"] . ", " . $value["time"] . "<br>";
}

How to change pivot table data source in Excel?

right click on the pivot table in excel choose wizard click 'back' click 'get data...' in the query window File - Table Definition

then you can create a new or choose a different connection

Callback when DOM is loaded in react.js

You can watch your container element using the useRef hook. Note that you need to watch the ref's current value specifically, otherwise it won't work.

Example:

  const containerRef = useRef();
  const { current } = containerRef;

  useEffect(setLinksData, [current]);

return (
    <div ref={containerRef}>
      // your child elements...
    </div>
)

AngularJS - difference between pristine/dirty and touched/untouched

$pristine/$dirty tells you whether the user actually changed anything, while $touched/$untouched tells you whether the user has merely been there/visited.

This is really useful for validation. The reason for $dirty was always to avoid showing validation responses until the user has actually visited a certain control. But, by using only the $dirty property, the user wouldn't get validation feedback unless they actually altered the value. So, an $invalid field still wouldn't show the user a prompt if the user didn't change/interact with the value. If the user entirely ignored a required field, everything looked OK.

With Angular 1.3 and ng-touched, you can now set a particular style on a control as soon as the user has blurred, regardless of whether they actually edited the value or not.

Here's a CodePen that shows the difference in behavior.

DateTime.MinValue and SqlDateTime overflow

Very simple avoid using DateTime.MinValue use System.Data.SqlTypes.SqlDateTime.MinValue instead.

What is the maximum length of a String in PHP?

In a new upcoming php7 among many other features, they added a support for strings bigger than 2^31 bytes:

Support for strings with length >= 2^31 bytes in 64 bit builds.

Sadly they did not specify how much bigger can it be.

Is there any simple way to convert .xls file to .csv file? (Excel)

I need to do the same thing. I ended up with something similar to Kman

       static void ExcelToCSVCoversion(string sourceFile,  string targetFile)
    {
        Application rawData = new Application();

        try
        {
            Workbook workbook = rawData.Workbooks.Open(sourceFile);
            Worksheet ws = (Worksheet) workbook.Sheets[1];
            ws.SaveAs(targetFile, XlFileFormat.xlCSV);
            Marshal.ReleaseComObject(ws);
        }

        finally
        {
            rawData.DisplayAlerts = false;
            rawData.Quit();
            Marshal.ReleaseComObject(rawData);
        }


        Console.WriteLine();
        Console.WriteLine($"The excel file {sourceFile} has been converted into {targetFile} (CSV format).");
        Console.WriteLine();
    }

If there are multiple sheets this is lost in the conversion but you could loop over the number of sheets and save each one as csv.

Convert seconds value to hours minutes seconds?

This is my simple solution:

String secToTime(int sec) {
    int seconds = sec % 60;
    int minutes = sec / 60;
    if (minutes >= 60) {
        int hours = minutes / 60;
        minutes %= 60;
        if( hours >= 24) {
            int days = hours / 24;
            return String.format("%d days %02d:%02d:%02d", days,hours%24, minutes, seconds);
        }
        return String.format("%02d:%02d:%02d", hours, minutes, seconds);
    }
    return String.format("00:%02d:%02d", minutes, seconds);
}

Test Results:

Result: 00:00:36 - 36
Result: 01:00:07 - 3607
Result: 6313 days 12:39:05 - 545488745

How do I disable right click on my web page?

You can do that with JavaScript by adding an event listener for the "contextmenu" event and calling the preventDefault() method:

document.addEventListener('contextmenu', event => event.preventDefault());

That being said: DON'T DO IT.

Why? Because it achieves nothing other than annoying users. Also many browsers have a security option to disallow disabling of the right click (context) menu anyway.

Not sure why you'd want to. If it's out of some misplaced belief that you can protect your source code or images that way, think again: you can't.

Show image using file_get_contents

Do i need to modify the headers and just echo it or something?

exactly.

Send a header("content-type: image/your_image_type"); and the data afterwards.

How to parse the Manifest.mbdb file in an iOS 4.0 iTunes Backup

Thank you, user374559 and reneD -- that code and description is very helpful.

My stab at some Python to parse and print out the information in a Unix ls-l like format:

#!/usr/bin/env python
import sys

def getint(data, offset, intsize):
    """Retrieve an integer (big-endian) and new offset from the current offset"""
    value = 0
    while intsize > 0:
        value = (value<<8) + ord(data[offset])
        offset = offset + 1
        intsize = intsize - 1
    return value, offset

def getstring(data, offset):
    """Retrieve a string and new offset from the current offset into the data"""
    if data[offset] == chr(0xFF) and data[offset+1] == chr(0xFF):
        return '', offset+2 # Blank string
    length, offset = getint(data, offset, 2) # 2-byte length
    value = data[offset:offset+length]
    return value, (offset + length)

def process_mbdb_file(filename):
    mbdb = {} # Map offset of info in this file => file info
    data = open(filename).read()
    if data[0:4] != "mbdb": raise Exception("This does not look like an MBDB file")
    offset = 4
    offset = offset + 2 # value x05 x00, not sure what this is
    while offset < len(data):
        fileinfo = {}
        fileinfo['start_offset'] = offset
        fileinfo['domain'], offset = getstring(data, offset)
        fileinfo['filename'], offset = getstring(data, offset)
        fileinfo['linktarget'], offset = getstring(data, offset)
        fileinfo['datahash'], offset = getstring(data, offset)
        fileinfo['unknown1'], offset = getstring(data, offset)
        fileinfo['mode'], offset = getint(data, offset, 2)
        fileinfo['unknown2'], offset = getint(data, offset, 4)
        fileinfo['unknown3'], offset = getint(data, offset, 4)
        fileinfo['userid'], offset = getint(data, offset, 4)
        fileinfo['groupid'], offset = getint(data, offset, 4)
        fileinfo['mtime'], offset = getint(data, offset, 4)
        fileinfo['atime'], offset = getint(data, offset, 4)
        fileinfo['ctime'], offset = getint(data, offset, 4)
        fileinfo['filelen'], offset = getint(data, offset, 8)
        fileinfo['flag'], offset = getint(data, offset, 1)
        fileinfo['numprops'], offset = getint(data, offset, 1)
        fileinfo['properties'] = {}
        for ii in range(fileinfo['numprops']):
            propname, offset = getstring(data, offset)
            propval, offset = getstring(data, offset)
            fileinfo['properties'][propname] = propval
        mbdb[fileinfo['start_offset']] = fileinfo
    return mbdb

def process_mbdx_file(filename):
    mbdx = {} # Map offset of info in the MBDB file => fileID string
    data = open(filename).read()
    if data[0:4] != "mbdx": raise Exception("This does not look like an MBDX file")
    offset = 4
    offset = offset + 2 # value 0x02 0x00, not sure what this is
    filecount, offset = getint(data, offset, 4) # 4-byte count of records 
    while offset < len(data):
        # 26 byte record, made up of ...
        fileID = data[offset:offset+20] # 20 bytes of fileID
        fileID_string = ''.join(['%02x' % ord(b) for b in fileID])
        offset = offset + 20
        mbdb_offset, offset = getint(data, offset, 4) # 4-byte offset field
        mbdb_offset = mbdb_offset + 6 # Add 6 to get past prolog
        mode, offset = getint(data, offset, 2) # 2-byte mode field
        mbdx[mbdb_offset] = fileID_string
    return mbdx

def modestr(val):
    def mode(val):
        if (val & 0x4): r = 'r'
        else: r = '-'
        if (val & 0x2): w = 'w'
        else: w = '-'
        if (val & 0x1): x = 'x'
        else: x = '-'
        return r+w+x
    return mode(val>>6) + mode((val>>3)) + mode(val)

def fileinfo_str(f, verbose=False):
    if not verbose: return "(%s)%s::%s" % (f['fileID'], f['domain'], f['filename'])
    if (f['mode'] & 0xE000) == 0xA000: type = 'l' # symlink
    elif (f['mode'] & 0xE000) == 0x8000: type = '-' # file
    elif (f['mode'] & 0xE000) == 0x4000: type = 'd' # dir
    else: 
        print >> sys.stderr, "Unknown file type %04x for %s" % (f['mode'], fileinfo_str(f, False))
        type = '?' # unknown
    info = ("%s%s %08x %08x %7d %10d %10d %10d (%s)%s::%s" % 
            (type, modestr(f['mode']&0x0FFF) , f['userid'], f['groupid'], f['filelen'], 
             f['mtime'], f['atime'], f['ctime'], f['fileID'], f['domain'], f['filename']))
    if type == 'l': info = info + ' -> ' + f['linktarget'] # symlink destination
    for name, value in f['properties'].items(): # extra properties
        info = info + ' ' + name + '=' + repr(value)
    return info

verbose = True
if __name__ == '__main__':
    mbdb = process_mbdb_file("Manifest.mbdb")
    mbdx = process_mbdx_file("Manifest.mbdx")
    for offset, fileinfo in mbdb.items():
        if offset in mbdx:
            fileinfo['fileID'] = mbdx[offset]
        else:
            fileinfo['fileID'] = "<nofileID>"
            print >> sys.stderr, "No fileID found for %s" % fileinfo_str(fileinfo)
        print fileinfo_str(fileinfo, verbose)

Android difference between Two Dates

I use this: send start and end date in millisecond

public int GetDifference(long start,long end){
    Calendar cal = Calendar.getInstance();
    cal.setTimeInMillis(start);
    int hour = cal.get(Calendar.HOUR_OF_DAY);
    int min = cal.get(Calendar.MINUTE);
    long t=(23-hour)*3600000+(59-min)*60000;

    t=start+t;

    int diff=0;
    if(end>t){
        diff=(int)((end-t)/ TimeUnit.DAYS.toMillis(1))+1;
    }

    return  diff;
}

Notepad++ add to every line

To append different text to the end of each line, you can use the plugin ConyEdit to do this.
With ConyEdit running in the background, follow these steps.

  1. use the command line cc.gl a to get lines and store in an array named a.
  2. use the command line cc.aal //$a to append after each line, using the contents of array a.

Example
enter image description here

CSS background image alt attribute

As mentioned in other answers, there is no (supported) alt attribute for a div tag only for the img tag.

The real question is why you need to add the alt attribute to all background images for the site? Based on this answer, it will help you determine which route to take in your approach.

Visual/Textual: If you are simply attempting to add a textual fall back for the user if the image fails to load, simply use the title attribute. Most browsers will provide a visual tool tip(message box) when a user hovers over the image, and if the image is not loaded for whatever reason, it behaves the same as an alt attribute presenting text when image fails. This technique still allows for the site to speed up load times by keeping images set to backgrounds.

Screen Readers: The middle of the road option, this varies because technically keeping your images as backgrounds and using the title attribute approach should work as hinted above, "Audio user agents may speak the title information in a similar context." However this is not guaranteed to work in all cases, including some readers may ignore it all together. If you end up opting for this approach, you can also try adding in aria-labels to help ensure screen readers pick these up.

SEO/Search Engines: Here is the big one, if you were like me, you added your background images, all was good. Then months later the customer(or maybe yourself) realized that you are missing out on some prime SEO gold by not having alt's for your images. Keep in mind, the title attribute does not have any weight on search engines, from my research and as mentioned in an article here: https://www.searchenginejournal.com/how-to-use-link-title-attribute-correctly/. So if you are aiming for SEO, then you will need to have an img tag with the alt attribute. One possible approach is to just load very small actual images on the site with alt attributes, this way you get all the SEO and don't have to readjust the existing CSS in place. However this may lead to additional load time depending on the size and google does indeed look at the images path when indexing. In short if you are going this route, just accept what has to be done and include the actual images instead of using backgrounds.

Maven: How to change path to target directory from command line?

Colin is correct that a profile should be used. However, his answer hard-codes the target directory in the profile. An alternate solution would be to add a profile like this:

    <profile>
        <id>alternateBuildDir</id>
        <activation>
            <property>
                <name>alt.build.dir</name>
            </property>
        </activation>
        <build>
            <directory>${alt.build.dir}</directory>
        </build>
    </profile>

Doing so would have the effect of changing the build directory to whatever is given by the alt.build.dir property, which can be given in a POM, in the user's settings, or on the command line. If the property is not present, the compilation will happen in the normal target directory.

Search for "does-not-contain" on a DataFrame in pandas

I had to get rid of the NULL values before using the command recommended by Andy above. An example:

df = pd.DataFrame(index = [0, 1, 2], columns=['first', 'second', 'third'])
df.ix[:, 'first'] = 'myword'
df.ix[0, 'second'] = 'myword'
df.ix[2, 'second'] = 'myword'
df.ix[1, 'third'] = 'myword'
df

    first   second  third
0   myword  myword   NaN
1   myword  NaN      myword 
2   myword  myword   NaN

Now running the command:

~df["second"].str.contains(word)

I get the following error:

TypeError: bad operand type for unary ~: 'float'

I got rid of the NULL values using dropna() or fillna() first and retried the command with no problem.

Caching a jquery ajax response in javascript/browser

        function getDatas() {
            let cacheKey = 'memories';

            if (cacheKey in localStorage) {
                let datas = JSON.parse(localStorage.getItem(cacheKey));

                // if expired
                if (datas['expires'] < Date.now()) {
                    localStorage.removeItem(cacheKey);

                    getDatas()
                } else {
                    setDatas(datas);
                }
            } else {
                $.ajax({
                    "dataType": "json",
                    "success": function(datas, textStatus, jqXHR) {
                        let today = new Date();

                        datas['expires'] = today.setDate(today.getDate() + 7) // expires in next 7 days

                        setDatas(datas);

                        localStorage.setItem(cacheKey, JSON.stringify(datas));
                    },
                    "url": "http://localhost/phunsanit/snippets/PHP/json.json_encode.php",
                });
            }
        }

        function setDatas(datas) {
            // display json as text
            $('#datasA').text(JSON.stringify(datas));

            // your code here
           ....

        }

        // call
        getDatas();

enter link description here

Convert dictionary values into array

// dict is Dictionary<string, Foo>

Foo[] foos = new Foo[dict.Count];
dict.Values.CopyTo(foos, 0);

// or in C# 3.0:
var foos = dict.Values.ToArray();

How to get index of object by its property in JavaScript?

a prototypical way

(function(){
  if (!Array.prototype.indexOfPropertyValue){
    Array.prototype.indexOfPropertyValue = function(prop,value){
      for (var index = 0; index < this.length; index++){
        if (this[index][prop]){
          if (this[index][prop] == value){
            return index;
          }
        }
      }
      return -1;
    }
  }
 })();
 // usage:
 var Data = [
 {id_list:1, name:'Nick',token:'312312'},{id_list:2,name:'John',token:'123123'}];
 Data.indexOfPropertyValue('name','John'); // returns 1 (index of array);
 Data.indexOfPropertyValue('name','Invalid name') // returns -1 (no result);
 var indexOfArray = Data.indexOfPropertyValue('name','John');
 Data[indexOfArray] // returns desired object.

Check last modified date of file in C#

Just use File.GetLastWriteTime. There's a sample on that page showing how to use it.

Creating a zero-filled pandas data frame

If you already have a dataframe, this is the fastest way:

In [1]: columns = ["col{}".format(i) for i in range(10)]
In [2]: orig_df = pd.DataFrame(np.ones((10, 10)), columns=columns)
In [3]: %timeit d = pd.DataFrame(np.zeros_like(orig_df), index=orig_df.index, columns=orig_df.columns)
10000 loops, best of 3: 60.2 µs per loop

Compare to:

In [4]: %timeit d = pd.DataFrame(0, index = np.arange(10), columns=columns)
10000 loops, best of 3: 110 µs per loop

In [5]: temp = np.zeros((10, 10))
In [6]: %timeit d = pd.DataFrame(temp, columns=columns)
10000 loops, best of 3: 95.7 µs per loop

paint() and repaint() in Java

Difference between Paint() and Repaint() method

Paint():

This method holds instructions to paint this component. Actually, in Swing, you should change paintComponent() instead of paint(), as paint calls paintBorder(), paintComponent() and paintChildren(). You shouldn't call this method directly, you should call repaint() instead.

Repaint():

This method can't be overridden. It controls the update() -> paint() cycle. You should call this method to get a component to repaint itself. If you have done anything to change the look of the component, but not its size ( like changing color, animating, etc. ) then call this method.

Add text to textarea - Jquery

That should work. Better if you pass a function to val:

$('#replyBox').val(function(i, text) {
    return text + quote;
});

This way you avoid searching the element and calling val twice.

Error: Generic Array Creation

You can't create arrays with a generic component type.

Create an array of an explicit type, like Object[], instead. You can then cast this to PCB[] if you want, but I don't recommend it in most cases.

PCB[] res = (PCB[]) new Object[list.size()]; /* Not type-safe. */

If you want type safety, use a collection like java.util.List<PCB> instead of an array.

By the way, if list is already a java.util.List, you should use one of its toArray() methods, instead of duplicating them in your code. This doesn't get your around the type-safety problem though.

Font scaling based on width of container

100% is relative to the base font size, which, if you haven't set it, would be the browser's user-agent default.

To get the effect you're after, I would use a piece of JavaScript code to adjust the base font size relative to the window dimensions.

How to make a simple popup box in Visual C#?

Try this:

string text = "My text that I want to display";
MessageBox.Show(text);

Reference - What does this error mean in PHP?

Parse error: syntax error, unexpected T_PAAMAYIM_NEKUDOTAYIM

The scope resolution operator is also called "Paamayim Nekudotayim" from the Hebrew ?????? ?????????. which means "double colon".

This error typically happens if you inadvertently put :: in your code.

Related Questions:

Documentation:

MySQL order by before group by

Try this one. Just get the list of latest post dates from each author. Thats it

SELECT wp_posts.* FROM wp_posts WHERE wp_posts.post_status='publish'
AND wp_posts.post_type='post' AND wp_posts.post_date IN(SELECT MAX(wp_posts.post_date) FROM wp_posts GROUP BY wp_posts.post_author) 

How to find out when a particular table was created in Oracle?

You copy and paste the following code. It will display all the tables with Name and Created Date

SELECT object_name,created FROM user_objects
WHERE object_name LIKE  '%table_name%'
AND object_type = 'TABLE'; 

Note: Replace '%table_name%' with the table name you are looking for.

How to get height and width of device display in angular2 using typescript?

I found the solution. The answer is very simple. write the below code in your constructor.

import { Component, OnInit, OnDestroy, Input } from "@angular/core";
// Import this, and write at the top of your .ts file
import { HostListener } from "@angular/core";

@Component({
  selector: "app-login",
  templateUrl: './login.component.html',
  styleUrls: ['./login.component.css']
})

export class LoginComponent implements OnInit, OnDestroy {
    // Declare height and width variables
    scrHeight:any;
    scrWidth:any;

    @HostListener('window:resize', ['$event'])
    getScreenSize(event?) {
          this.scrHeight = window.innerHeight;
          this.scrWidth = window.innerWidth;
          console.log(this.scrHeight, this.scrWidth);
    }

    // Constructor
    constructor() {
        this.getScreenSize();
    }


}

====== Working Code (Another) ======

export class Dashboard  {
 mobHeight: any;
 mobWidth: any;
     constructor(private router:Router, private http: Http){
        this.mobHeight = (window.screen.height) + "px";
        this.mobWidth = (window.screen.width) + "px";
          console.log(this.mobHeight);
          console.log(this.mobWidth)
     }
}

How do I tell Spring Boot which main class to use for the executable jar?

If you are using Grade, it is possible to apply the 'application' plugin rather than the 'java' plugin. This allows specifying the main class as below without using any Spring Boot Gradle plugin tasks.

plugins {
  id 'org.springframework.boot' version '2.3.3.RELEASE'
  id 'io.spring.dependency-management' version '1.0.10.RELEASE'
  id 'application'
}
application {
  mainClassName = 'com.example.ExampleApplication'
}

As a nice benefit, one is able to run the application using gradle run with the classpath automatically configured by Gradle. The plugin also packages the application as a TAR and/or ZIP including operating system specific start scripts.

Sending GET request with Authentication headers using restTemplate

All of these answers appear to be incomplete and/or kludges. Looking at the RestTemplate interface, it sure looks like it is intended to have a ClientHttpRequestFactory injected into it, and then that requestFactory will be used to create the request, including any customizations of headers, body, and request params.

You either need a universal ClientHttpRequestFactory to inject into a single shared RestTemplate or else you need to get a new template instance via new RestTemplate(myHttpRequestFactory).

Unfortunately, it looks somewhat non-trivial to create such a factory, even when you just want to set a single Authorization header, which is pretty frustrating considering what a common requirement that likely is, but at least it allows easy use if, for example, your Authorization header can be created from data contained in a Spring-Security Authorization object, then you can create a factory that sets the outgoing AuthorizationHeader on every request by doing SecurityContextHolder.getContext().getAuthorization() and then populating the header, with null checks as appropriate. Now all outbound rest calls made with that RestTemplate will have the correct Authorization header.

Without more emphasis placed on the HttpClientFactory mechanism, providing simple-to-overload base classes for common cases like adding a single header to requests, most of the nice convenience methods of RestTemplate end up being a waste of time, since they can only rarely be used.

I'd like to see something simple like this made available

@Configuration
public class MyConfig {
  @Bean
  public RestTemplate getRestTemplate() {
    return new RestTemplate(new AbstractHeaderRewritingHttpClientFactory() {
        @Override
        public HttpHeaders modifyHeaders(HttpHeaders headers) {
          headers.addHeader("Authorization", computeAuthString());
          return headers;
        }
        public String computeAuthString() {
          // do something better than this, but you get the idea
          return SecurityContextHolder.getContext().getAuthorization().getCredential();
        }
    });
  }
}

At the moment, the interface of the available ClientHttpRequestFactory's are harder to interact with than that. Even better would be an abstract wrapper for existing factory implementations which makes them look like a simpler object like AbstractHeaderRewritingRequestFactory for the purposes of replacing just that one piece of functionality. Right now, they are very general purpose such that even writing those wrappers is a complex piece of research.

Sample database for exercise

You want huge?

Here's a small table: create table foo (id int not null primary key auto_increment, crap char(2000));

insert into foo(crap) values ('');

-- each time you run the next line, the number of rows in foo doubles. insert into foo( crap ) select * from foo;

run it twenty more times, you have over a million rows to play with.

Yes, if he's looking for looks of relations to navigate, this is not the answer. But if by huge he means to test performance and his ability to optimize, this will do it. I did exactly this (and then updated with random values) to test an potential answer I had for another question. (And didn't answer it, because I couldn't come up with better performance than what that asker had.)

Had he asked for "complex", I'd have gien a differnt answer. To me,"huge" implies "lots of rows".

Because you don't need huge to play with tables and relations. Consider a table, by itself, with no nullable columns. How many different kinds of rows can there be? Only one, as all columns must have some value as none can be null.

Every nullable column multiples by two the number of different kinds of rows possible: a row where that column is null, an row where it isn't null.

Now consider the table, not in isolation. Consider a table that is a child table: for every child that has an FK to the parent, that, is a many-to-one, there can be 0, 1 or many children. So we multiply by three times the count we got in the previous step (no rows for zero, one for exactly one, two rows for many). For any grandparent to which the parent is a many, another three.

For many-to-many relations, we can have have no relation, a one-to-one, a one-to-many, many-to-one, or a many-to-many. So for each many-to-many we can reach in a graph from the table, we multiply the rows by nine -- or just like two one-to manys. If the many-to-many also has data, we multiply by the nullability number.

Tables that we can't reach in our graph -- those that we have no direct or indirect FK to, don't multiply the rows in our table.

By recursively multiplying the each table we can reach, we can come up with the number of rows needed to provide one of each "kind", and we need no more than those to test every possible relation in our schema. And we're nowhere near huge.

PYTHONPATH on Linux

PYTHONPATH is an environment variable those content is added to the sys.path where Python looks for modules. You can set it to whatever you like.

However, do not mess with PYTHONPATH. More often than not, you are doing it wrong and it will only bring you trouble in the long run. For example, virtual environments could do strange things…

I would suggest you learned how to package a Python module properly, maybe using this easy setup. If you are especially lazy, you could use cookiecutter to do all the hard work for you.

Typing Greek letters etc. in Python plots

Not only can you add raw strings to matplotlib but you can also specify the font in matplotlibrc or locally with:

from matplotlib import rc

rc('font', **{'family':'serif','serif':['Palatino']})
rc('text', usetex=True)

This would change your serif latex font. You can also specify the sans-serif Helvetica like so

rc('font',**{'family':'sans-serif','sans-serif':['Helvetica']})

Other options are cursive and monospace with their respective font names. Your label would then be

fig.gca().set_xlabel(r'wavelength $5000 \AA$')

If the font doesn't supply an Angstrom symbol you can try using \mathring{A}

libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)

CMYR - "his could also happen if you've wired up a button to an IBAction that doesn't exist anymore (or has been renamed)"

If you're running into this problem make sure that you go to Main.storyboard, RIGHT click on the yellow box icon (view controller) at the top of the phone outline and DELETE the outlet(s) with yellow flags.

What happens in instances like this is you probably named an action, then renamed it. You need to delete the old name and if that was the only issue will start right up in sim!

enter image description here

Select Last Row in the Table

Use the latest scope provided by Laravel out of the box.

Model::latest()->first();

That way you're not retrieving all the records. A nicer shortcut to orderBy.

handling dbnull data in vb.net

You can also use the Convert.ToString() and Convert.ToInteger() methods to convert items with DB null effectivly.

Looking for a good Python Tree data structure

I think, from my own experience on problems with more advanced data structures, that the most important thing you can do here, is to get a good knowledge on the general concept of tress as data structures. If you understand the basic mechanism behind the concept it will be quite easy to implement the solution that fits your problem. There are a lot of good sources out there describing the concept. What "saved" me years ago on this particular problem was section 2.3 in "The Art of Computer Programming".

Unexpected character encountered while parsing value

I solved the problem with these online tools:

  1. To check if the Json structure is OKAY: http://jsonlint.com/
  2. To generate my Object class from my Json structure: https://www.jsonutils.com/

The simple code:

RootObject rootObj= JsonConvert.DeserializeObject<RootObject>(File.ReadAllText(pathFile));

MySQL TEXT vs BLOB vs CLOB

TEXT is a data-type for text based input. On the other hand, you have BLOB and CLOB which are more suitable for data storage (images, etc) due to their larger capacity limits (4GB for example).

As for the difference between BLOB and CLOB, I believe CLOB has character encoding associated with it, which implies it can be suited well for very large amounts of text.

BLOB and CLOB data can take a long time to retrieve, relative to how quick data from a TEXT field can be retrieved. So, use only what you need.

Mysql: Select all data between two dates

You can use as an alternate solution:

SELECT * FROM TABLE_NAME WHERE `date` >= '1-jan-2013' 
OR `date` <= '12-jan-2013'

Font size relative to the user's screen resolution?

You might try this tool: http://fittextjs.com/

I haven't used this second tool, but it seems similar: https://github.com/zachleat/BigText

Checking if float is an integer

Keep in mind that most of the techniques here are valid presuming that round-off error due to prior calculations is not a factor. E.g. you could use roundf, like this:

float z = 1.0f;

if (roundf(z) == z) {
    printf("integer\n");
} else {
    printf("fraction\n");
}

The problem with this and other similar techniques (such as ceilf, casting to long, etc.) is that, while they work great for whole number constants, they will fail if the number is a result of a calculation that was subject to floating-point round-off error. For example:

float z = powf(powf(3.0f, 0.05f), 20.0f);

if (roundf(z) == z) {
    printf("integer\n");
} else {
    printf("fraction\n");
}

Prints "fraction", even though (31/20)20 should equal 3, because the actual calculation result ended up being 2.9999992847442626953125.

Any similar method, be it fmodf or whatever, is subject to this. In applications that perform complex or rounding-prone calculations, usually what you want to do is define some "tolerance" value for what constitutes a "whole number" (this goes for floating-point equality comparisons in general). We often call this tolerance epsilon. For example, lets say that we'll forgive the computer for up to +/- 0.00001 rounding error. Then, if we are testing z, we can choose an epsilon of 0.00001 and do:

if (fabsf(roundf(z) - z) <= 0.00001f) {
    printf("integer\n");
} else {
    printf("fraction\n");
}

You don't really want to use ceilf here because e.g. ceilf(1.0000001) is 2 not 1, and ceilf(-1.99999999) is -1 not -2.

You could use rintf in place of roundf if you prefer.

Choose a tolerance value that is appropriate for your application (and yes, sometimes zero tolerance is appropriate). For more information, check out this article on comparing floating-point numbers.

Take a screenshot via a Python script on Linux

import ImageGrab
img = ImageGrab.grab()
img.save('test.jpg','JPEG')

this requires Python Imaging Library

Is it possible to disable scrolling on a ViewPager

import android.content.Context;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.animation.DecelerateInterpolator;
import android.widget.Scroller;
import java.lang.reflect.Field;

public class NonSwipeableViewPager extends ViewPager {

public NonSwipeableViewPager(Context context) {
    super(context);
}

public NonSwipeableViewPager(Context context, AttributeSet attrs) {
    super(context, attrs);
}

@Override
public boolean onInterceptTouchEvent(MotionEvent event) {
    // stop swipe 
    return false;
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    // stop switching pages
    return false;
}

private void setMyScroller() {
    try {
        Class<?> viewpager = ViewPager.class;
        Field scroller = viewpager.getDeclaredField("mScroller");
        scroller.setAccessible(true);
        scroller.set(this, new MyScroller(getContext()));
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public class MyScroller extends Scroller {
    public MyScroller(Context context) {
        super(context, new DecelerateInterpolator());
    }

    @Override
    public void startScroll(int startX, int startY, int dx, int dy, int 
duration) {
        super.startScroll(startX, startY, dx, dy, 350 /*1 secs*/);
    }
}
}

Then in your Layout.XML file replace any --- com.android.support.V4.ViewPager --- tags with --- com.yourpackage.NonSwipeableViewPager --- tags.

getElementsByClassName not working

If you want to do it by ClassName you could do:

<script type="text/javascript">
function hideTd(className){
    var elements;

    if (document.getElementsByClassName)
    {
        elements = document.getElementsByClassName(className);
    }
    else
    {
        var elArray = [];
        var tmp = document.getElementsByTagName(elements);  
        var regex = new RegExp("(^|\\s)" + className+ "(\\s|$)");
        for ( var i = 0; i < tmp.length; i++ ) {

            if ( regex.test(tmp[i].className) ) {
                elArray.push(tmp[i]);
            }
        }

        elements = elArray;
    }

    for(var i = 0, i < elements.length; i++) {
       if( elements[i].textContent == ''){
          elements[i].style.display = 'none';
       } 
    }

  }
</script>

How do I concatenate multiple C++ strings on one line?

Here's the one-liner solution:

#include <iostream>
#include <string>

int main() {
  std::string s = std::string("Hi") + " there" + " friends";
  std::cout << s << std::endl;

  std::string r = std::string("Magic number: ") + std::to_string(13) + "!";
  std::cout << r << std::endl;

  return 0;
}

Although it's a tiny bit ugly, I think it's about as clean as you cat get in C++.

We are casting the first argument to a std::string and then using the (left to right) evaluation order of operator+ to ensure that its left operand is always a std::string. In this manner, we concatenate the std::string on the left with the const char * operand on the right and return another std::string, cascading the effect.

Note: there are a few options for the right operand, including const char *, std::string, and char.

It's up to you to decide whether the magic number is 13 or 6227020800.

What is the advantage of using REST instead of non-REST HTTP?

  • Give every “resource” an ID
  • Link things together
  • Use standard methods
  • Resources with multiple representations
  • Communicate statelessly

It is possible to do everything just with POST and GET? Yes, is it the best approach? No, why? because we have standards methods. If you think again, it would be possible to do everything using just GET.. so why should we even bother do use POST? Because of the standards!

For example, today thinking about a MVC model, you can limit your application to respond just to specific kinds of verbs like POST, GET, PUT and DELETE. Even if under the hood everything is emulated to POST and GET, don't make sense to have different verbs for different actions?

How do I remove diacritics (accents) from a string in .NET?

It's funny such a question can get so many answers, and yet none fit my requirements :) There are so many languages around, a full language agnostic solution is AFAIK not really possible, as others has mentionned that the FormC or FormD are giving issues.

Since the original question was related to French, the simplest working answer is indeed

    public static string ConvertWesternEuropeanToASCII(this string str)
    {
        return Encoding.ASCII.GetString(Encoding.GetEncoding(1251).GetBytes(str));
    }

1251 should be replaced by the encoding code of the input language.

This however replace only one character by one character. Since I am also working with German as input, I did a manual convert

    public static string LatinizeGermanCharacters(this string str)
    {
        StringBuilder sb = new StringBuilder(str.Length);
        foreach (char c in str)
        {
            switch (c)
            {
                case 'ä':
                    sb.Append("ae");
                    break;
                case 'ö':
                    sb.Append("oe");
                    break;
                case 'ü':
                    sb.Append("ue");
                    break;
                case 'Ä':
                    sb.Append("Ae");
                    break;
                case 'Ö':
                    sb.Append("Oe");
                    break;
                case 'Ü':
                    sb.Append("Ue");
                    break;
                case 'ß':
                    sb.Append("ss");
                    break;
                default:
                    sb.Append(c);
                    break;
            }
        }
        return sb.ToString();
    }

It might not deliver the best performance, but at least it is very easy to read and extend. Regex is a NO GO, much slower than any char/string stuff.

I also have a very simple method to remove space:

    public static string RemoveSpace(this string str)
    {
        return str.Replace(" ", string.Empty);
    }

Eventually, I am using a combination of all 3 above extensions:

    public static string LatinizeAndConvertToASCII(this string str, bool keepSpace = false)
    {
        str = str.LatinizeGermanCharacters().ConvertWesternEuropeanToASCII();            
        return keepSpace ? str : str.RemoveSpace();
    }

And a small unit test to that (not exhaustive) which pass successfully.

    [TestMethod()]
    public void LatinizeAndConvertToASCIITest()
    {
        string europeanStr = "Bonjour ça va? C'est l'été! Ich möchte ä Ä á à â ê é è ë Ë É ï Ï î í ì ó ò ô ö Ö Ü ü ù ú û Û ý Ý ç Ç ñ Ñ";
        string expected = "Bonjourcava?C'estl'ete!IchmoechteaeAeaaaeeeeEEiIiiiooooeOeUeueuuuUyYcCnN";
        string actual = europeanStr.LatinizeAndConvertToASCII();
        Assert.AreEqual(expected, actual);
    }

LoDash: Get an array of values from an array of object properties

With pure JS:

var userIds = users.map( function(obj) { return obj.id; } );

Index inside map() function

You will be able to get the current iteration's index for the map method through its 2nd parameter.

Example:

const list = [ 'h', 'e', 'l', 'l', 'o'];
list.map((currElement, index) => {
  console.log("The current iteration is: " + index);
  console.log("The current element is: " + currElement);
  console.log("\n");
  return currElement; //equivalent to list[index]
});

Output:

The current iteration is: 0 <br>The current element is: h

The current iteration is: 1 <br>The current element is: e

The current iteration is: 2 <br>The current element is: l

The current iteration is: 3 <br>The current element is: l 

The current iteration is: 4 <br>The current element is: o

See also: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array/map

Parameters

callback - Function that produces an element of the new Array, taking three arguments:

1) currentValue
The current element being processed in the array.

2) index
The index of the current element being processed in the array.

3) array
The array map was called upon.

How to include vars file in a vars file with ansible?

You can put your servers in the default_step group and those vars will apply to it:

# inventory file
[default_step]
prod2
web_v2

Then just move your default_step.yml file to group_vars/default_step.yml.

Enabling WiFi on Android Emulator

The emulator does not provide virtual hardware for Wi-Fi if you use API 24 or earlier. From the Android Developers website:

When using an AVD with API level 25 or higher, the emulator provides a simulated Wi-Fi access point ("AndroidWifi"), and Android automatically connects to it.

You can disable Wi-Fi in the emulator by running the emulator with the command-line parameter -feature -Wifi.

https://developer.android.com/studio/run/emulator.html#wi-fi

What's not supported

The Android Emulator doesn't include virtual hardware for the following:

  • Bluetooth
  • NFC
  • SD card insert/eject
  • Device-attached headphones
  • USB

The watch emulator for Android Wear doesn't support the Overview (Recent Apps) button, D-pad, and fingerprint sensor.

(read more at https://developer.android.com/studio/run/emulator.html#about)

https://developer.android.com/studio/run/emulator.html#wi-fi

Is it possible to remove the hand cursor that appears when hovering over a link? (or keep it set as the normal pointer)

<style>
a{
cursor: default;
}
</style>

In the above code [cursor:default] is used. Default is the usual arrow cursor that appears.

And if you use [cursor: pointer] then you can access to the hand like cursor that appears when you hover over a link.

To know more about cursors and their appearance click the below link: https://www.w3schools.com/cssref/pr_class_cursor.asp

Finding all possible combinations of numbers to reach a given sum

I thought I'd use an answer from this question but I couldn't, so here is my answer. It is using a modified version of an answer in Structure and Interpretation of Computer Programs. I think this is a better recursive solution and should please the purists more.

My answer is in Scala (and apologies if my Scala sucks, I've just started learning it). The findSumCombinations craziness is to sort and unique the original list for the recursion to prevent dupes.

def findSumCombinations(target: Int, numbers: List[Int]): Int = {
  cc(target, numbers.distinct.sortWith(_ < _), List())
}

def cc(target: Int, numbers: List[Int], solution: List[Int]): Int = {
  if (target == 0) {println(solution); 1 }
  else if (target < 0 || numbers.length == 0) 0
  else 
    cc(target, numbers.tail, solution) 
    + cc(target - numbers.head, numbers, numbers.head :: solution)
}

To use it:

 > findSumCombinations(12345, List(1,5,22,15,0,..))
 * Prints a whole heap of lists that will sum to the target *