Programs & Examples On #Meta inf

The META-INF directory related to .jar file contain the manifest (list of contents) of a jar and is created when you write a jar file.

What's the purpose of META-INF?

From the official JAR File Specification (link goes to the Java 7 version, but the text hasn't changed since at least v1.3):

The META-INF directory

The following files/directories in the META-INF directory are recognized and interpreted by the Java 2 Platform to configure applications, extensions, class loaders and services:

  • MANIFEST.MF

The manifest file that is used to define extension and package related data.

  • INDEX.LIST

This file is generated by the new "-i" option of the jar tool, which contains location information for packages defined in an application or extension. It is part of the JarIndex implementation and used by class loaders to speed up their class loading process.

  • x.SF

The signature file for the JAR file. 'x' stands for the base file name.

  • x.DSA

The signature block file associated with the signature file with the same base file name. This file stores the digital signature of the corresponding signature file.

  • services/

This directory stores all the service provider configuration files.

Load RSA public key from file

Below is the relevant information from the link which Zaki provided.

Generate a 2048-bit RSA private key

$ openssl genrsa -out private_key.pem 2048

Convert private Key to PKCS#8 format (so Java can read it)

$ openssl pkcs8 -topk8 -inform PEM -outform DER -in private_key.pem -out private_key.der -nocrypt

Output public key portion in DER format (so Java can read it)

$ openssl rsa -in private_key.pem -pubout -outform DER -out public_key.der

Private key

import java.io.*;
import java.nio.*;
import java.security.*;
import java.security.spec.*;

public class PrivateKeyReader {

  public static PrivateKey get(String filename)
  throws Exception {

    byte[] keyBytes = Files.readAllBytes(Paths.get(filename));

    PKCS8EncodedKeySpec spec =
      new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    return kf.generatePrivate(spec);
  }
}

Public key

import java.io.*;
import java.nio.*;
import java.security.*;
import java.security.spec.*;

public class PublicKeyReader {

  public static PublicKey get(String filename)
    throws Exception {

    byte[] keyBytes = Files.readAllBytes(Paths.get(filename));

    X509EncodedKeySpec spec =
      new X509EncodedKeySpec(keyBytes);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    return kf.generatePublic(spec);
  }
}

Download/Stream file from URL - asp.net

If you are looking for a .NET Core version of @Dallas's answer, use the below.

        Stream stream = null;

        //This controls how many bytes to read at a time and send to the client
        int bytesToRead = 10000;

        // Buffer to read bytes in chunk size specified above
        byte[] buffer = new Byte[bytesToRead];

        // The number of bytes read
        try
        {
            //Create a WebRequest to get the file
            HttpWebRequest fileReq = (HttpWebRequest)HttpWebRequest.Create(@"file url");

            //Create a response for this request
            HttpWebResponse fileResp = (HttpWebResponse)fileReq.GetResponse();

            if (fileReq.ContentLength > 0)
                fileResp.ContentLength = fileReq.ContentLength;

            //Get the Stream returned from the response
            stream = fileResp.GetResponseStream();

            // prepare the response to the client. resp is the client Response
            var resp = HttpContext.Response;

            //Indicate the type of data being sent
            resp.ContentType = "application/octet-stream";

            //Name the file 
            resp.Headers.Add("Content-Disposition", "attachment; filename=test.zip");
            resp.Headers.Add("Content-Length", fileResp.ContentLength.ToString());

            int length;
            do
            {
                // Verify that the client is connected.
                if (!HttpContext.RequestAborted.IsCancellationRequested)
                {
                    // Read data into the buffer.
                    length = stream.Read(buffer, 0, bytesToRead);

                    // and write it out to the response's output stream
                    resp.Body.Write(buffer, 0, length);


                    //Clear the buffer
                    buffer = new Byte[bytesToRead];
                }
                else
                {
                    // cancel the download if client has disconnected
                    length = -1;
                }
            } while (length > 0); //Repeat until no data is read
        }
        finally
        {
            if (stream != null)
            {
                //Close the input stream
                stream.Close();
            }
        }

How does the "final" keyword in Java work? (I can still modify an object.)

This is a favorite interview question. With this questions, the interviewer tries to find out how well you understand the behavior of objects with respect to constructors, methods, class variables (static variables) and instance variables.

import java.util.ArrayList;
import java.util.List;

class Test {
    private final List foo;

    public Test() {
        foo = new ArrayList();
        foo.add("foo"); // Modification-1
    }

    public void setFoo(List foo) {
       //this.foo = foo; Results in compile time error.
    }
}

In the above case, we have defined a constructor for 'Test' and gave it a 'setFoo' method.

About constructor: Constructor can be invoked only one time per object creation by using the new keyword. You cannot invoke constructor multiple times, because constructor are not designed to do so.

About method: A method can be invoked as many times as you want (Even never) and the compiler knows it.

Scenario 1

private final List foo;  // 1

foo is an instance variable. When we create Test class object then the instance variable foo, will be copied inside the object of Test class. If we assign foo inside the constructor, then the compiler knows that the constructor will be invoked only once, so there is no problem assigning it inside the constructor.

If we assign foo inside a method, the compiler knows that a method can be called multiple times, which means the value will have to be changed multiple times, which is not allowed for a final variable. So the compiler decides constructor is good choice! You can assign a value to a final variable only one time.

Scenario 2

private static final List foo = new ArrayList();

foo is now a static variable. When we create an instance of Test class, foo will not be copied to the object because foo is static. Now foo is not an independent property of each object. This is a property of Test class. But foo can be seen by multiple objects and if every object which is created by using the new keyword which will ultimately invoke the Test constructor which changes the value at the time of multiple object creation (Remember static foo is not copied in every object, but is shared between multiple objects.)

Scenario 3

t.foo.add("bar"); // Modification-2

Above Modification-2 is from your question. In the above case, you are not changing the first referenced object, but you are adding content inside foo which is allowed. Compiler complains if you try to assign a new ArrayList() to the foo reference variable.
Rule If you have initialized a final variable, then you cannot change it to refer to a different object. (In this case ArrayList)

final classes cannot be subclassed
final methods cannot be overridden. (This method is in superclass)
final methods can override. (Read this in grammatical way. This method is in a subclass)

How to remove .html from URL?

Good question, but it seems to have confused people. The answers are almost equally divided between those who thought Dave (the OP) was saving his HTML pages without the .html extension, and those who thought he was saving them as normal (with .html), but wanting the URL to show up without. While the question could have been worded a little better, I think it’s clear what he meant. If he was saving pages without .html, his two question (‘how to remove .html') and (how to ‘redirect any url with .html’) would be exactly the same question! So that interpretation doesn’t make much sense. Also, his first comment (about avoiding an infinite loop) and his own answer seem to confirm this.

So let’s start by rephrasing the question and breaking down the task. We want to accomplish two things:

  1. Visibly remove the .html if it’s part of the requested URL (e.g. /page.html)
  2. Point the cropped URL (e.g. /page) back to the actual file (/page.html).

There’s nothing difficult about doing either of these things. (We could achieve the second one simply by enabling MultiViews.) The challenge here is doing them both without creating an infinite loop.

Dave’s own answer got the job done, but it’s pretty convoluted and not at all portable. (Sorry Dave.) Lukasz Habrzyk seems to have cleaned up Anmol’s answer, and finally Amit Verma improved on them both. However, none of them explained how their solutions solved the fundamental problem—how to avoid an infinite loop. As I understand it, they work because THE_REQUEST variable holds the original request from the browser. As such, the condition (RewriteCond %{THE_REQUEST}) only gets triggered once. Since it doesn’t get triggered upon a rewrite, you avoid the infinite loop scenario. But then you're dealing with the full HTTP request—GET, HTTP and all—which partly explains some of the uglier regex examples on this page.

I’m going to offer one more approach, which I think is easier to understand. I hope this helps future readers understand the code they’re using, rather than just copying and pasting code they barely understand and hoping for the best.

RewriteEngine on

# Remove .html (or htm) from visible URL (permanent redirect)
RewriteCond %{REQUEST_URI} ^/(.+)\.html?$ [nocase]
RewriteRule ^ /%1 [L,R=301]

# Quietly point back to the HTML file (temporary/undefined redirect):
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}.html -f
RewriteRule ^ %{REQUEST_URI}.html [END]

Let’s break it down…

The first rule is pretty simple. The condition matches any URL ending in .html (or .htm) and redirects to the URL without the filename extension. It's a permanent redirect to indicate that the cropped URL is the canonical one.

The second rule is simple too. The first condition will only pass if the requested filename is not a valid directory (!-d). The second will only pass if the filename refers to a valid file (-f) with the .html extension added. If both conditions pass, the rewrite rule simply adds ‘.html’ to the filename. And then the magic happens… [END]. Yep, that’s all it takes to prevent an infinite loop. The Apache RewriteRule Flags documentation explains it:

Using the [END] flag terminates not only the current round of rewrite processing (like [L]) but also prevents any subsequent rewrite processing from occurring in per-directory (htaccess) context.

Difference between acceptance test and functional test?

The difference is between testing the problem and the solution. Software is a solution to a problem, both can be tested.

The functional test confirms the software performs a function within the boundaries of how you've solved the problem. This is an integral part of developing software, comparable to the testing that is done on mass produced product before it leaves the factory. A functional test verifies that the product actually works as you (the developer) think it does.

Acceptance tests verify the product actually solves the problem it was made to solve. This can best be done by the user (customer), for instance performing his/her tasks that the software assists with. If the software passes this real world test, it's accepted to replace the previous solution. This acceptance test can sometimes only be done properly in production, especially if you have anonymous customers (e.g. a website). Thus a new feature will only be accepted after days or weeks of use.

Functional testing - test the product, verifying that it has the qualities you've designed or build (functions, speed, errors, consistency, etc.)

Acceptance testing - test the product in its context, this requires (simulation of) human interaction, test it has the desired effect on the original problem(s).

Steps to send a https request to a rest service in Node js

The easiest way is to use the request module.

request('https://example.com/url?a=b', function (error, response, body) {
  if (!error && response.statusCode == 200) {
    console.log(body);
  }
});

How to load image files with webpack file-loader

Regarding problem #1

Once you have the file-loader configured in the webpack.config, whenever you use import/require it tests the path against all loaders, and in case there is a match it passes the contents through that loader. In your case, it matched

{
    test: /\.(jpe?g|png|gif|svg)$/i, 
    loader: "file-loader?name=/public/icons/[name].[ext]"
}

// For newer versions of Webpack it should be
{
    test: /\.(jpe?g|png|gif|svg)$/i, 
    loader: 'file-loader',
    options: {
      name: '/public/icons/[name].[ext]'
    }
}

and therefore you see the image emitted to

dist/public/icons/imageview_item_normal.png

which is the wanted behavior.

The reason you are also getting the hash file name, is because you are adding an additional inline file-loader. You are importing the image as:

'file!../../public/icons/imageview_item_normal.png'.

Prefixing with file!, passes the file into the file-loader again, and this time it doesn't have the name configuration.

So your import should really just be:

import img from '../../public/icons/imageview_item_normal.png'

Update

As noted by @cgatian, if you actually want to use an inline file-loader, ignoring the webpack global configuration, you can prefix the import with two exclamation marks (!!):

import '!!file!../../public/icons/imageview_item_normal.png'.

Regarding problem #2

After importing the png, the img variable only holds the path the file-loader "knows about", which is public/icons/[name].[ext] (aka "file-loader? name=/public/icons/[name].[ext]"). Your output dir "dist" is unknown. You could solve this in two ways:

  1. Run all your code under the "dist" folder
  2. Add publicPath property to your output config, that points to your output directory (in your case ./dist).

Example:

output: {
  path: PATHS.build,
  filename: 'app.bundle.js',
  publicPath: PATHS.build
},

import httplib ImportError: No module named httplib

You are running Python 2 code on Python 3. In Python 3, the module has been renamed to http.client.

You could try to run the 2to3 tool on your code, and try to have it translated automatically. References to httplib will automatically be rewritten to use http.client instead.

What is the difference between Trap and Interrupt?

A Trap can be identified as a transfer of control, which is initiated by the programmer. The term Trap is used interchangeably with the term Exception (which is an automatically occurring software interrupt). But some may argue that a trap is simply a special subroutine call. So they fall in to the category of software-invoked interrupts. For example, in 80×86 machines, a programmer can use the int instruction to initiate a trap. Because a trap is always unconditional the control will always be transferred to the subroutine associated with the trap. The exact instruction, which invokes the routine for handling the trap is easily identified because an explicit instruction is used to specify a trap.

Angular get object from array by Id

CASE - 1

Using array.filter() We can get an array of objects which will match with our condition.
see the working example.

_x000D_
_x000D_
var questions = [
      {id: 1, question: "Do you feel a connection to a higher source and have a sense of comfort knowing that you are part of something greater than yourself?", category: "Spiritual", subs: []},
      {id: 2, question: "Do you feel you are free of unhealthy behavior that impacts your overall well-being?", category: "Habits", subs: []},
      {id: 3, question: "1 Do you feel you have healthy and fulfilling relationships?", category: "Relationships", subs: []},
      {id: 3, question: "2 Do you feel you have healthy and fulfilling relationships?", category: "Relationships", subs: []},
      {id: 3, question: "3 Do you feel you have healthy and fulfilling relationships?", category: "Relationships", subs: []},
      {id: 4, question: "Do you feel you have a sense of purpose and that you have a positive outlook about yourself and life?", category: "Emotional Well-being", subs: []},
      {id: 5, question: "Do you feel you have a healthy diet and that you are fueling your body for optimal health? ", category: "Eating Habits ", subs: []},
      {id: 6, question: "Do you feel that you get enough rest and that your stress level is healthy?", category: "Relaxation ", subs: []},
      {id: 7, question: "Do you feel you get enough physical activity for optimal health?", category: "Exercise ", subs: []},
      {id: 8, question: "Do you feel you practice self-care and go to the doctor regularly?", category: "Medical Maintenance", subs: []},
      {id: 9, question: "Do you feel satisfied with your income and economic stability?", category: "Financial", subs: []},
      {id: 10, question: "1 Do you feel you do fun things and laugh enough in your life?", category: "Play", subs: []},
      {id: 10, question: "2 Do you feel you do fun things and laugh enough in your life?", category: "Play", subs: []},
      {id: 11, question: "Do you feel you have a healthy sense of balance in this area of your life?", category: "Work-life Balance", subs: []},
      {id: 12, question: "Do you feel a sense of peace and contentment  in your home? ", category: "Home Environment", subs: []},
      {id: 13, question: "Do you feel that you are challenged and growing as a person?", category: "Intellectual Wellbeing", subs: []},
      {id: 14, question: "Do you feel content with what you see when you look in the mirror?", category: "Self-image", subs: []},
      {id: 15, question: "Do you feel engaged at work and a sense of fulfillment with your job?", category: "Work Satisfaction", subs: []}
];

function filter(){
  console.clear();
  var filter_id = document.getElementById("filter").value;
  var filter_array = questions.filter(x => x.id == filter_id);
  console.log(filter_array);
}
_x000D_
button {
  background: #0095ff;
  color: white;
  border: none;
  border-radius: 3px;
  padding: 8px;
  cursor: pointer;
}

input {
  padding: 8px;
}
_x000D_
<div>
  <label for="filter"></label>
  <input id="filter" type="number" name="filter" placeholder="Enter id which you want to filter">
  <button onclick="filter()">Filter</button>
</div>
_x000D_
_x000D_
_x000D_

CASE - 2

Using array.find() we can get first matched item and break the iteration.

_x000D_
_x000D_
var questions = [
      {id: 1, question: "Do you feel a connection to a higher source and have a sense of comfort knowing that you are part of something greater than yourself?", category: "Spiritual", subs: []},
      {id: 2, question: "Do you feel you are free of unhealthy behavior that impacts your overall well-being?", category: "Habits", subs: []},
      {id: 3, question: "1 Do you feel you have healthy and fulfilling relationships?", category: "Relationships", subs: []},
      {id: 3, question: "2 Do you feel you have healthy and fulfilling relationships?", category: "Relationships", subs: []},
      {id: 3, question: "3 Do you feel you have healthy and fulfilling relationships?", category: "Relationships", subs: []},
      {id: 4, question: "Do you feel you have a sense of purpose and that you have a positive outlook about yourself and life?", category: "Emotional Well-being", subs: []},
      {id: 5, question: "Do you feel you have a healthy diet and that you are fueling your body for optimal health? ", category: "Eating Habits ", subs: []},
      {id: 6, question: "Do you feel that you get enough rest and that your stress level is healthy?", category: "Relaxation ", subs: []},
      {id: 7, question: "Do you feel you get enough physical activity for optimal health?", category: "Exercise ", subs: []},
      {id: 8, question: "Do you feel you practice self-care and go to the doctor regularly?", category: "Medical Maintenance", subs: []},
      {id: 9, question: "Do you feel satisfied with your income and economic stability?", category: "Financial", subs: []},
      {id: 10, question: "1 Do you feel you do fun things and laugh enough in your life?", category: "Play", subs: []},
      {id: 10, question: "2 Do you feel you do fun things and laugh enough in your life?", category: "Play", subs: []},
      {id: 11, question: "Do you feel you have a healthy sense of balance in this area of your life?", category: "Work-life Balance", subs: []},
      {id: 12, question: "Do you feel a sense of peace and contentment  in your home? ", category: "Home Environment", subs: []},
      {id: 13, question: "Do you feel that you are challenged and growing as a person?", category: "Intellectual Wellbeing", subs: []},
      {id: 14, question: "Do you feel content with what you see when you look in the mirror?", category: "Self-image", subs: []},
      {id: 15, question: "Do you feel engaged at work and a sense of fulfillment with your job?", category: "Work Satisfaction", subs: []}
];

function find(){
  console.clear();
  var find_id = document.getElementById("find").value;
  var find_object = questions.find(x => x.id == find_id);
  console.log(find_object);
}
_x000D_
button {
  background: #0095ff;
  color: white;
  border: none;
  border-radius: 3px;
  padding: 8px;
  cursor: pointer;
}

input {
  padding: 8px;
  width: 200px;
}
_x000D_
<div>
  <label for="find"></label>
  <input id="find" type="number" name="find" placeholder="Enter id which you want to find">
  <button onclick="find()">Find</button>
</div>
_x000D_
_x000D_
_x000D_

writing integer values to a file using out.write()

any of these should work

outf.write("%s" % num)

outf.write(str(num))

print >> outf, num

How to hide 'Back' button on navigation bar on iPhone?

In the function viewDidLoad of the UIViewController use the code:

self.navigationItem.hidesBackButton = YES;

dropping rows from dataframe based on a "not in" condition

You can use pandas.Dataframe.isin.

pandas.Dateframe.isin will return boolean values depending on whether each element is inside the list a or not. You then invert this with the ~ to convert True to False and vice versa.

import pandas as pd

a = ['2015-01-01' , '2015-02-01']

df = pd.DataFrame(data={'date':['2015-01-01' , '2015-02-01', '2015-03-01' , '2015-04-01', '2015-05-01' , '2015-06-01']})

print(df)
#         date
#0  2015-01-01
#1  2015-02-01
#2  2015-03-01
#3  2015-04-01
#4  2015-05-01
#5  2015-06-01

df = df[~df['date'].isin(a)]

print(df)
#         date
#2  2015-03-01
#3  2015-04-01
#4  2015-05-01
#5  2015-06-01

R - test if first occurrence of string1 is followed by string2

> grepl("^[^_]+_1",s)
[1] FALSE
> grepl("^[^_]+_2",s)
[1] TRUE

basically, look for everything at the beginning except _, and then the _2.

+1 to @Ananda_Mahto for suggesting grepl instead of grep.

MySQL update CASE WHEN/THEN/ELSE

If id is sequential starting at 1, the simplest (and quickest) would be:

UPDATE `table` 
SET uid = ELT(id, 2952, 4925, 1592) 
WHERE id IN (1,2,3)

As ELT() returns the Nth element of the list of strings: str1 if N = 1, str2 if N = 2, and so on. Returns NULL if N is less than 1 or greater than the number of arguments.

Clearly, the above code only works if id is 1, 2, or 3. If id was 10, 20, or 30, either of the following would work:

UPDATE `table` 
SET uid = CASE id 
WHEN 10 THEN 2952 
WHEN 20 THEN 4925 
WHEN 30 THEN 1592 END CASE 
WHERE id IN (10, 20, 30)

or the simpler:

UPDATE `table` 
SET uid = ELT(FIELD(id, 10, 20, 30), 2952, 4925, 1592) 
WHERE id IN (10, 20, 30)

As FIELD() returns the index (position) of str in the str1, str2, str3, ... list. Returns 0 if str is not found.

Rubymine: How to make Git ignore .idea files created by Rubymine

Close PHP Storm in terminal go to the project folder type

git rm -rf .idea; git commit -m "delete .idea"; git push;

Then go to project folder and delete the folder .idea

sudo rm -r .idea/

Start PhpStorm and you are done

How can I use break or continue within for loop in Twig template?

From docs TWIG docs:

Unlike in PHP, it's not possible to break or continue in a loop.

But still:

You can however filter the sequence during iteration which allows you to skip items.

Example 1 (for huge lists you can filter posts using slice, slice(start, length)):

{% for post in posts|slice(0,10) %}
    <h2>{{ post.heading }}</h2>
{% endfor %}

Example 2:

{% for post in posts if post.id < 10 %}
    <h2>{{ post.heading }}</h2>
{% endfor %}

You can even use own TWIG filters for more complexed conditions, like:

{% for post in posts|onlySuperPosts %}
    <h2>{{ post.heading }}</h2>
{% endfor %}

How to check if a std::string is set or not?

You can't; at least not the same way you can test whether a pointer is NULL.

A std::string object is always initialized and always contains a string; its contents by default are an empty string ("").

You can test for emptiness (using s.size() == 0 or s.empty()).

How to make a SIMPLE C++ Makefile

I suggest (note that the indent is a TAB):

tool: tool.o file1.o file2.o
    $(CXX) $(LDFLAGS) $^ $(LDLIBS) -o $@

or

LINK.o = $(CXX) $(LDFLAGS) $(TARGET_ARCH)
tool: tool.o file1.o file2.o

The latter suggestion is slightly better since it reuses GNU Make implicit rules. However, in order to work, a source file must have the same name as the final executable (i.e.: tool.c and tool).

Notice, it is not necessary to declare sources. Intermediate object files are generated using implicit rule. Consequently, this Makefile work for C and C++ (and also for Fortran, etc...).

Also notice, by default, Makefile use $(CC) as the linker. $(CC) does not work for linking C++ object files. We modify LINK.o only because of that. If you want to compile C code, you don't have to force the LINK.o value.

Sure, you can also add your compilation flags with variable CFLAGS and add your libraries in LDLIBS. For example:

CFLAGS = -Wall
LDLIBS = -lm

One side note: if you have to use external libraries, I suggest to use pkg-config in order to correctly set CFLAGS and LDLIBS:

CFLAGS += $(shell pkg-config --cflags libssl)
LDLIBS += $(shell pkg-config --libs libssl)

The attentive reader will notice that this Makefile does not rebuild properly if one header is changed. Add these lines to fix the problem:

override CPPFLAGS += -MMD
include $(wildcard *.d)

-MMD allows to build .d files that contains Makefile fragments about headers dependencies. The second line just uses them.

For sure, a well written Makefile should also include clean and distclean rules:

clean:
    $(RM) *.o *.d

distclean: clean
    $(RM) tool

Notice, $(RM) is the equivalent of rm -f, but it is a good practice to not call rm directly.

The all rule is also appreciated. In order to work, it should be the first rule of your file:

all: tool

You may also add an install rule:

PREFIX = /usr/local
install:
    install -m 755 tool $(DESTDIR)$(PREFIX)/bin

DESTDIR is empty by default. The user can set it to install your program at an alternative system (mandatory for cross-compilation process). Package maintainers for multiple distribution may also change PREFIX in order to install your package in /usr.

One final word: Do not place source files in sub-directories. If you really want to do that, keep this Makefile in the root directory and use full paths to identify your files (i.e. subdir/file.o).

So to summarise, your full Makefile should look like:

LINK.o = $(CXX) $(LDFLAGS) $(TARGET_ARCH)
PREFIX = /usr/local
override CPPFLAGS += -MMD
include $(wildcard *.d)

all: tool
tool: tool.o file1.o file2.o
clean:
    $(RM) *.o *.d
distclean: clean
    $(RM) tool
install:
    install -m 755 tool $(DESTDIR)$(PREFIX)/bin

Div Background Image Z-Index Issue

To solve the issue, you are using the z-index on the footer and header, but you forgot about the position, if a z-index is to be used, the element must have a position:

Add to your footer and header this CSS:

position: relative; 

EDITED:

Also noticed that the background image on the #backstretch has a negative z-index, don't use that, some browsers get really weird...

Remove From the #backstretch:

z-index: -999999;

Read a little bit about Z-Index here!

how to get right offset of an element? - jQuery

Brendon Crawford had the best answer here (in comment), so I'll move it to an answer until he does (and maybe expand a little).

var offset = $('#whatever').offset();

offset.right = $(window).width() - (offset.left + $('#whatever').outerWidth(true));
offset.bottom = $(window).height() - (offset.top + $('#whatever').outerHeight(true));

How to debug JavaScript / jQuery event bindings with Firebug or similar tools?

jQuery stores events in the following:

$("a#somefoo").data("events")

Doing a console.log($("a#somefoo").data("events")) should list the events attached to that element.

How can I echo a newline in a batch file?

You can use @echo ( @echo + [space] + [insecable space] )

Note: The insecable space can be obtained with Alt+0160

Hope it helps :)

[edit] Hmm you're right, I needed it in a Makefile, it works perfectly in there. I guess my answer is not adapted for batch files... My bad.

How to yum install Node.JS on Amazon Linux

For those who want to have the accepted answer run in Ansible without further searches, I post the task here for convenience and future reference.

Accepted answer recommendation: https://stackoverflow.com/a/35165401/78935

Ansible task equivalent

tasks:
  - name: Setting up the NodeJS yum repository
    shell: curl --silent --location https://rpm.nodesource.com/setup_10.x | bash -
    args:
      warn: no
  # ...

How to wrap text using CSS?

With text-wrap, browser support is relatively weak (as you might expect from from a draft spec).

You are better off taking steps to ensure the data doesn't have long strings of non-white-space.

How to Generate Barcode using PHP and Display it as an Image on the same page

There is a library for this BarCode PHP. You just need to include a few files:

require_once('class/BCGFontFile.php');
require_once('class/BCGColor.php');
require_once('class/BCGDrawing.php');

You can generate many types of barcodes, namely 1D or 2D. Add the required library:

require_once('class/BCGcode39.barcode.php');

Generate the colours:

// The arguments are R, G, and B for color.
$colorFront = new BCGColor(0, 0, 0);
$colorBack = new BCGColor(255, 255, 255);

After you have added all the codes, you will get this way:

Example

Since several have asked for an example here is what I was able to do to get it done

require_once('class/BCGFontFile.php');
require_once('class/BCGColor.php');
require_once('class/BCGDrawing.php');

require_once('class/BCGcode128.barcode.php');

header('Content-Type: image/png');

$color_white = new BCGColor(255, 255, 255);

$code = new BCGcode128();
$code->parse('HELLO');

$drawing = new BCGDrawing('', $color_white);
$drawing->setBarcode($code);

$drawing->draw();
$drawing->finish(BCGDrawing::IMG_FORMAT_PNG);

If you want to actually create the image file so you can save it then change

$drawing = new BCGDrawing('', $color_white);

to

$drawing = new BCGDrawing('image.png', $color_white);

Python module os.chmod(file, 664) does not change the permission to rw-rw-r-- but -w--wx----

So for people who want semantics similar to:

$ chmod 755 somefile

Use:

$ python -c "import os; os.chmod('somefile', 0o755)"

If your Python is older than 2.6:

$ python -c "import os; os.chmod('somefile', 0755)"

When should I use Lazy<T>?

Just to point onto the example posted by Mathew

public sealed class Singleton
{
    // Because Singleton's constructor is private, we must explicitly
    // give the Lazy<Singleton> a delegate for creating the Singleton.
    private static readonly Lazy<Singleton> instanceHolder =
        new Lazy<Singleton>(() => new Singleton());

    private Singleton()
    {
        ...
    }

    public static Singleton Instance
    {
        get { return instanceHolder.Value; }
    }
}

before the Lazy was born we would have done it this way:

private static object lockingObject = new object();
public static LazySample InstanceCreation()
{
    if(lazilyInitObject == null)
    {
         lock (lockingObject)
         {
              if(lazilyInitObject == null)
              {
                   lazilyInitObject = new LazySample ();
              }
         }
    }
    return lazilyInitObject ;
}

jquery variable syntax

self and $self aren't the same. The former is the object pointed to by "this" and the latter a jQuery object whose "scope" is the object pointed to by "this". Similarly, $body isn't the body DOM element but the jQuery object whose scope is the body element.

Running npm command within Visual Studio Code

  1. Edit user setting file settings.json.
    • Settings > Search for settings.json > Edit in settings.json
    or
    • Run > type %APPDATA%\Code\User\settings.json
  2. Copy this code
    { "terminal.integrated.shell.windows": "C:\\Windows\\System32\\cmd.exe", "terminal.integrated.shellArgs.windows": ["/k nodevars.bat"] }
  3. Restart VS Code

How do I concatenate a string with a variable?

Your code is correct. Perhaps your problem is that you are not passing an ID to the AddBorder function, or that an element with that ID does not exist. Or you might be running your function before the element in question is accessible through the browser's DOM.

To identify the first case or determine the cause of the second case, add these as the first lines inside the function:

alert('ID number: ' + id);
alert('Return value of gEBI: ' + document.getElementById('horseThumb_' + id));

That will open pop-up windows each time the function is called, with the value of id and the return value of document.getElementById. If you get undefined for the ID number pop-up, you are not passing an argument to the function. If the ID does not exist, you would get your (incorrect?) ID number in the first pop-up but get null in the second.

The third case would happen if your web page looks like this, trying to run AddBorder while the page is still loading:

<head>
<title>My Web Page</title>
<script>
    function AddBorder(id) {
        ...
    }
    AddBorder(42);    // Won't work; the page hasn't completely loaded yet!
</script>
</head>

To fix this, put all the code that uses AddBorder inside an onload event handler:

// Can only have one of these per page
window.onload = function() {
    ...
    AddBorder(42);
    ...
} 

// Or can have any number of these on a page
function doWhatever() {
   ...
   AddBorder(42);
   ...
}

if(window.addEventListener) window.addEventListener('load', doWhatever, false);
else window.attachEvent('onload', doWhatever);

Invoking JavaScript code in an iframe from the parent page

Calling a parent JS function from iframe is possible, but only when both the parent and the page loaded in the iframe are from same domain i.e. abc.com, and both are using same protocol i.e. both are either on http:// or https://.

The call will fail in below mentioned cases:

  1. Parent page and the iframe page are from different domain.
  2. They are using different protocols, one is on http:// and other is on https://.

Any workaround to this restriction would be extremely insecure.

For instance, imagine I registered the domain superwinningcontest.com and sent out links to people's emails. When they loaded up the main page, I could hide a few iframes in there and read their Facebook feed, check recent Amazon or PayPal transactions, or--if they used a service that did not implement sufficient security--transfer money out of their accounts. That's why JavaScript is limited to same-domain and same-protocol.

Matplotlib - global legend and title aside subplots

In addition to the orbeckst answer one might also want to shift the subplots down. Here's an MWE in OOP style:

import matplotlib.pyplot as plt

fig = plt.figure()
st = fig.suptitle("suptitle", fontsize="x-large")

ax1 = fig.add_subplot(311)
ax1.plot([1,2,3])
ax1.set_title("ax1")

ax2 = fig.add_subplot(312)
ax2.plot([1,2,3])
ax2.set_title("ax2")

ax3 = fig.add_subplot(313)
ax3.plot([1,2,3])
ax3.set_title("ax3")

fig.tight_layout()

# shift subplots down:
st.set_y(0.95)
fig.subplots_adjust(top=0.85)

fig.savefig("test.png")

gives:

enter image description here

How to convert a DataTable to a string in C#?

i know i'm years late xD but Here's how i did it

    public static string convertDataTableToString(DataTable dataTable)
    {
        string data = string.Empty;
        for (int i = 0; i < dataTable.Rows.Count; i++)
        {
            DataRow row = dataTable.Rows[i];
            for (int j = 0; j < dataTable.Columns.Count; j++)
            {
                data += dataTable.Columns[j].ColumnName + "~" + row[j];
                if (j == dataTable.Columns.Count - 1)
                {
                    if (i != (dataTable.Rows.Count - 1))
                        data += "$";
                }
                else
                    data += "|";
            }
        }
        return data;
    }

If someone ever optimizes this please let me know

i tried this :

    public static string convertDataTableToString(DataTable dataTable)
    {
        string data = string.Empty;
        int rowsCount = dataTable.Rows.Count;
        for (int i = 0; i < rowsCount; i++)
        {
            DataRow row = dataTable.Rows[i];
            int columnsCount = dataTable.Columns.Count;
            for (int j = 0; j < columnsCount; j++)
            {
                data += dataTable.Columns[j].ColumnName + "~" + row[j];
                if (j == columnsCount - 1)
                {
                    if (i != (rowsCount - 1))
                        data += "$";
                }
                else
                    data += "|";
            }
        }
        return data;
    }

but this answer says it's worse

How to put a new line into a wpf TextBlock control?

you must use

 < SomeObject xml:space="preserve" > once upon a time ...
      this line will be below the first one < /SomeObject>

Or if you prefer :

 <SomeObject xml:space="preserve" />  once upon a time... &#10; this line below < / SomeObject>

watch out : if you both use &10 AND you go to the next line in your text, you'll have TWO empty lines.

here for details : http://msdn.microsoft.com/en-us/library/ms788746.aspx

How to make flexbox items the same size?

You could add flex-basis: 100% to achieve this.

Updated Example

.header {
  display: flex;
}

.item {
  flex-basis: 100%;
  text-align: center;
  border: 1px solid black;
}

For what it's worth, you could also use flex: 1 for the same results as well.

The shorthand of flex: 1 is the same as flex: 1 1 0, which is equivalent to:

.item {
  flex-grow: 1;
  flex-shrink: 1;
  flex-basis: 0;
  text-align: center;
  border: 1px solid black;
}

How do I check which version of NumPy I'm using?

If you're using NumPy from the Anaconda distribution, then you can just do:

$ conda list | grep numpy
numpy     1.11.3     py35_0

This gives the Python version as well.


If you want something fancy, then use numexpr

It gives lot of information as you can see below:

In [692]: import numexpr

In [693]: numexpr.print_versions()
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Numexpr version:   2.6.2
NumPy version:     1.13.3
Python version:    3.6.3 |Anaconda custom (64-bit)|
                   (default, Oct 13 2017, 12:02:49)
[GCC 7.2.0]
Platform:          linux-x86_64
AMD/Intel CPU?     True
VML available?     False
Number of threads used by default: 8 (out of 48 detected cores)
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

Creating CSS Global Variables : Stylesheet theme management

Latest Update: 16/01/2020

CSS Custom Properties (Variables) have arrived!

It's 2020 and time to officially roll out this feature in your new applications.


Preprocessor "NOT" required!

There is a lot of repetition in CSS. A single color may be used in several places.

For some CSS declarations, it is possible to declare this higher in the cascade and let CSS inheritance solve this problem naturally.

For non-trivial projects, this is not always possible. By declaring a variable on the :root pseudo-element, a CSS author can halt some instances of repetition by using the variable.

How it works

Set your variable at the top of your stylesheet:

CSS

Create a root class:

:root {
}

Create variables (-- [String] : [value])

:root {
  --red: #b00;
  --blue: #00b;
  --fullwidth: 100%;
}

Set your variables anywhere in your CSS document:

h1 {
  color: var(--red);
}
#MyText {
  color: var(--blue);
  width: var(--fullwidth);
}

BROWSER SUPPORT / COMPATIBILITY

See caniuse.com for current compatability.

![supported browsers


Firefox: Version 31+ (Enabled by default)

Supported since 2014 (Leading the way as usual.)

More info from Mozilla


Chrome: Version 49+ (Enabled by default).

Supported since 2016


Safari/IOS Safari: Version 9.1/9.3 (Enabled by default).

Supported since 2016


Opera: Version 39+ (Enabled by default).

Supported since 2016


Android: Version 52+ (Enabled by default).

Supported since 2016


Edge: Version 15+ (Enabled by default).

Supported since 2017

CSS Custom Properties landed in Windows Insider Preview build 14986


IE: When pigs fly.

It's time to finally let this ship sink. No one enjoyed riding her anyway. ?


W3C SPEC

Full specification for upcoming CSS variables

Read more


TRY IT OUT

A fiddle and snippet are attached below for testing:

(It will only work with supported browsers.)

DEMO FIDDLE

_x000D_
_x000D_
:root {
  --red: #b00;
  --blue: #4679bd;
  --grey: #ddd;
  --W200: 200px;
  --Lft: left;
}
.Bx1,
.Bx2,
.Bx3,
.Bx4 {
  float: var(--Lft);
  width: var(--W200);
  height: var(--W200);
  margin: 10px;
  padding: 10px;
  border: 1px solid var(--red);
}
.Bx1 {
  color: var(--red);
  background: var(--grey);
}
.Bx2 {
  color: var(--grey);
  background: black;
}
.Bx3 {
  color: var(--grey);
  background: var(--blue);
}
.Bx4 {
  color: var(--grey);
  background: var(--red);
}
_x000D_
<p>If you see four square boxes then variables are working as expected.</p>

<div class="Bx1">I should be red text on grey background.</div>
<div class="Bx2">I should be grey text on black background.</div>
<div class="Bx3">I should be grey text on blue background.</div>
<div class="Bx4">I should be grey text on red background.</div>
_x000D_
_x000D_
_x000D_

how to pass data in an hidden field from one jsp page to another?

To pass the value you must included the hidden value value="hiddenValue" in the <input> statement like so:

<input type="hidden" id="thisField" name="inputName" value="hiddenValue">

Then you recuperate the hidden form value in the same way that you recuperate the value of visible input fields, by accessing the parameter of the request object. Here is an example:

This code goes on the page where you want to hide the value.

<form action="anotherPage.jsp" method="GET">
    <input type="hidden" id="thisField" name="inputName" value="hiddenValue">
<input type="submit">   
</form>

Then on the 'anotherPage.jsp' page you recuperate the value by calling the getParameter(String name) method of the implicit request object, as so:

<% String hidden = request.getParameter("inputName"); %>
The Hidden Value is <%=hidden %>

The output of the above script will be:

The Hidden Value is hiddenValue 

Where is the Docker daemon log?

If your OS is using systemd then you can view docker daemon log with:

sudo journalctl -fu docker.service

Calculating Distance between two Latitude and Longitude GeoCoordinates

When CPU/math computing power is limited:

There are times (such as in my work) when computing power is scarce (e.g. no floating point processor, working with small microcontrollers) where some trig functions can take an exorbitant amount of CPU time (e.g. 3000+ clock cycles), so when I only need an approximation, especially if if the CPU must not be tied up for a long time, I use this to minimize CPU overhead:

/**------------------------------------------------------------------------
 * \brief  Great Circle distance approximation in km over short distances.
 *
 * Can be off by as much as 10%.
 *
 * approx_distance_in_mi = sqrt(x * x + y * y)
 *
 * where x = 69.1 * (lat2 - lat1)
 * and y = 69.1 * (lon2 - lon1) * cos(lat1/57.3)
 *//*----------------------------------------------------------------------*/
double    ApproximateDisatanceBetweenTwoLatLonsInKm(
                  double lat1, double lon1,
                  double lat2, double lon2
                  ) {
    double  ldRadians, ldCosR, x, y;

    ldRadians = (lat1 / 57.3) * 0.017453292519943295769236907684886;
    ldCosR = cos(ldRadians);
    x = 69.1 * (lat2 - lat1);
    y = 69.1 * (lon2 - lon1) * ldCosR;

    return sqrt(x * x + y * y) * 1.609344;  /* Converts mi to km. */
}

Credit goes to https://github.com/kristianmandrup/geo_vectors/blob/master/Distance%20calc%20notes.txt.

How to find the mime type of a file in python?

I 've tried a lot of examples but with Django mutagen plays nicely.

Example checking if files is mp3

from mutagen.mp3 import MP3, HeaderNotFoundError  

try:
    audio = MP3(file)
except HeaderNotFoundError:
    raise ValidationError('This file should be mp3')

The downside is that your ability to check file types is limited, but it's a great way if you want not only check for file type but also to access additional information.

How to set JAVA_HOME in Mac permanently?

First, figure out where your java home is by running the command /usr/libexec/java_home -v <version> replacing with whatever version of OpenJDK your running.

Next use vim ~/.bash_profile to edit your bash profile. Add export JAVA_HOME="<java path>" replacing with the path to your java home found in the last step.

Finally, run the command source ~/.bash_profile

This should permanently set your JAVA_HOME environment variable.

To make sure it worked run echo $JAVA_HOME and make sure it returns the path you set

POST Multipart Form Data using Retrofit 2.0 including image

So its very simple way to achieve your task. You need to follow below step :-

1. First step

public interface APIService {  
    @Multipart
    @POST("upload")
    Call<ResponseBody> upload(
        @Part("item") RequestBody description,
        @Part("imageNumber") RequestBody description,
        @Part MultipartBody.Part imageFile
    );
}

You need to make the entire call as @Multipart request. item and image number is just string body which is wrapped in RequestBody. We use the MultipartBody.Part class that allows us to send the actual file name besides the binary file data with the request

2. Second step

  File file = (File) params[0];
  RequestBody requestFile = RequestBody.create(MediaType.parse("multipart/form-data"), file);

  MultipartBody.Part body =MultipartBody.Part.createFormData("Image", file.getName(), requestBody);

  RequestBody ItemId = RequestBody.create(okhttp3.MultipartBody.FORM, "22");
  RequestBody ImageNumber = RequestBody.create(okhttp3.MultipartBody.FORM,"1");
  final Call<UploadImageResponse> request = apiService.uploadItemImage(body, ItemId,ImageNumber);

Now you have image path and you need to convert into file.Now convert file into RequestBody using method RequestBody.create(MediaType.parse("multipart/form-data"), file). Now you need to convert your RequestBody requestFile into MultipartBody.Part using method MultipartBody.Part.createFormData("Image", file.getName(), requestBody); .

ImageNumber and ItemId is my another data which I need to send to server so I am also make both thing into RequestBody.

For more info

Access-Control-Allow-Origin Multiple Origin Domains?

I struggled to set this up for a domain running HTTPS, so I figured I would share the solution. I used the following directive in my httpd.conf file:

    <FilesMatch "\.(ttf|otf|eot|woff)$">
            SetEnvIf Origin "^http(s)?://(.+\.)?example\.com$" AccessControlAllowOrigin=$0
            Header set Access-Control-Allow-Origin %{AccessControlAllowOrigin}e env=AccessControlAllowOrigin
    </FilesMatch>

Change example.com to your domain name. Add this inside <VirtualHost x.x.x.x:xx> in your httpd.conf file. Notice that if your VirtualHost has a port suffix (e.g. :80) then this directive will not apply to HTTPS, so you will need to also go to /etc/apache2/sites-available/default-ssl and add the same directive in that file, inside of the <VirtualHost _default_:443> section.

Once the config files are updated, you will need to run the following commands in the terminal:

a2enmod headers
sudo service apache2 reload

Pointer arithmetic for void pointer in C

Compiler knows by type cast. Given a void *x:

  • x+1 adds one byte to x, pointer goes to byte x+1
  • (int*)x+1 adds sizeof(int) bytes, pointer goes to byte x + sizeof(int)
  • (float*)x+1 addres sizeof(float) bytes, etc.

Althought the first item is not portable and is against the Galateo of C/C++, it is nevertheless C-language-correct, meaning it will compile to something on most compilers possibly necessitating an appropriate flag (like -Wpointer-arith)

How to delete a folder with files using Java

private void deleteFileOrFolder(File file){
    try {
        for (File f : file.listFiles()) {
            f.delete();
            deleteFileOrFolder(f);
        }
    } catch (Exception e) {
        e.printStackTrace(System.err);
    }
}

Fill drop down list on selection of another drop down list

enter image description here

enter image description here

enter image description here

Model:

namespace MvcApplicationrazor.Models
{
    public class CountryModel
    {
        public List<State> StateModel { get; set; }
        public SelectList FilteredCity { get; set; }
    }
    public class State
    {
        public int Id { get; set; }
        public string StateName { get; set; }
    }
    public class City
    {
        public int Id { get; set; }
        public int StateId { get; set; }
        public string CityName { get; set; }
    }
}   

Controller:

public ActionResult Index()
        {
            CountryModel objcountrymodel = new CountryModel();
            objcountrymodel.StateModel = new List<State>();
            objcountrymodel.StateModel = GetAllState();
            return View(objcountrymodel);
        }


        //Action result for ajax call
        [HttpPost]
        public ActionResult GetCityByStateId(int stateid)
        {
            List<City> objcity = new List<City>();
            objcity = GetAllCity().Where(m => m.StateId == stateid).ToList();
            SelectList obgcity = new SelectList(objcity, "Id", "CityName", 0);
            return Json(obgcity);
        }
        // Collection for state
        public List<State> GetAllState()
        {
            List<State> objstate = new List<State>();
            objstate.Add(new State { Id = 0, StateName = "Select State" });
            objstate.Add(new State { Id = 1, StateName = "State 1" });
            objstate.Add(new State { Id = 2, StateName = "State 2" });
            objstate.Add(new State { Id = 3, StateName = "State 3" });
            objstate.Add(new State { Id = 4, StateName = "State 4" });
            return objstate;
        }
        //collection for city
        public List<City> GetAllCity()
        {
            List<City> objcity = new List<City>();
            objcity.Add(new City { Id = 1, StateId = 1, CityName = "City1-1" });
            objcity.Add(new City { Id = 2, StateId = 2, CityName = "City2-1" });
            objcity.Add(new City { Id = 3, StateId = 4, CityName = "City4-1" });
            objcity.Add(new City { Id = 4, StateId = 1, CityName = "City1-2" });
            objcity.Add(new City { Id = 5, StateId = 1, CityName = "City1-3" });
            objcity.Add(new City { Id = 6, StateId = 4, CityName = "City4-2" });
            return objcity;
        }

View:

@model MvcApplicationrazor.Models.CountryModel
@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/jquery-ui.min.js"></script>
<script language="javascript" type="text/javascript">
    function GetCity(_stateId) {
        var procemessage = "<option value='0'> Please wait...</option>";
        $("#ddlcity").html(procemessage).show();
        var url = "/Test/GetCityByStateId/";

        $.ajax({
            url: url,
            data: { stateid: _stateId },
            cache: false,
            type: "POST",
            success: function (data) {
                var markup = "<option value='0'>Select City</option>";
                for (var x = 0; x < data.length; x++) {
                    markup += "<option value=" + data[x].Value + ">" + data[x].Text + "</option>";
                }
                $("#ddlcity").html(markup).show();
            },
            error: function (reponse) {
                alert("error : " + reponse);
            }
        });

    }
</script>
<h4>
 MVC Cascading Dropdown List Using Jquery</h4>
@using (Html.BeginForm())
{
    @Html.DropDownListFor(m => m.StateModel, new SelectList(Model.StateModel, "Id", "StateName"), new { @id = "ddlstate", @style = "width:200px;", @onchange = "javascript:GetCity(this.value);" })
    <br />
    <br />
    <select id="ddlcity" name="ddlcity" style="width: 200px">

    </select>

    <br /><br />
  }

Resize Google Maps marker icon image

If the original size is 100 x 100 and you want to scale it to 50 x 50, use scaledSize instead of Size.

var icon = {
    url: "../res/sit_marron.png", // url
    scaledSize: new google.maps.Size(50, 50), // scaled size
    origin: new google.maps.Point(0,0), // origin
    anchor: new google.maps.Point(0, 0) // anchor
};

var marker = new google.maps.Marker({
    position: new google.maps.LatLng(lat, lng),
    map: map,
    icon: icon
});

How to use QueryPerformanceCounter?

Assuming you're on Windows (if so you should tag your question as such!), on this MSDN page you can find the source for a simple, useful HRTimer C++ class that wraps the needed system calls to do something very close to what you require (it would be easy to add a GetTicks() method to it, in particular, to do exactly what you require).

On non-Windows platforms, there's no QueryPerformanceCounter function, so the solution won't be directly portable. However, if you do wrap it in a class such as the above-mentioned HRTimer, it will be easier to change the class's implementation to use what the current platform is indeed able to offer (maybe via Boost or whatever!).

Detecting arrow key presses in JavaScript

Here's how I did it:

var leftKey = 37, upKey = 38, rightKey = 39, downKey = 40;
var keystate;
document.addEventListener("keydown", function (e) {
    keystate[e.keyCode] = true;
});
document.addEventListener("keyup", function (e) {
    delete keystate[e.keyCode];
});

if (keystate[leftKey]) {
//code to be executed when left arrow key is pushed.
}
if (keystate[upKey]) {
//code to be executed when up arrow key is pushed.
}
if (keystate[rightKey]) {
//code to be executed when right arrow key is pushed.
}
if (keystate[downKey]) {
//code to be executed when down arrow key is pushed.
}

How to find cube root using Python?

The best way is to use simple math

>>> a = 8
>>> a**(1./3.)
2.0

EDIT

For Negative numbers

>>> a = -8
>>> -(-a)**(1./3.)
-2.0

Complete Program for all the requirements as specified

x = int(input("Enter an integer: "))
if x>0:
    ans = x**(1./3.)
    if ans ** 3 != abs(x):
        print x, 'is not a perfect cube!'
else:
    ans = -((-x)**(1./3.))
    if ans ** 3 != -abs(x):
        print x, 'is not a perfect cube!'

print 'Cube root of ' + str(x) + ' is ' + str(ans)

Download a file by jQuery.Ajax

1. Framework agnostic: Servlet downloading file as attachment

<!-- with JS -->
<a href="javascript:window.location='downloadServlet?param1=value1'">
    download
</a>

<!-- without JS -->
<a href="downloadServlet?param1=value1" >download</a>

2. Struts2 Framework: Action downloading file as attachment

<!-- with JS -->
<a href="javascript:window.location='downloadAction.action?param1=value1'">
    download
</a>

<!-- without JS -->
<a href="downloadAction.action?param1=value1" >download</a>

It would be better to use <s:a> tag pointing with OGNL to an URL created with <s:url> tag:

<!-- without JS, with Struts tags: THE RIGHT WAY -->    
<s:url action="downloadAction.action" var="url">
    <s:param name="param1">value1</s:param>
</s:ulr>
<s:a href="%{url}" >download</s:a>

In the above cases, you need to write the Content-Disposition header to the response, specifying that the file needs to be downloaded (attachment) and not opened by the browser (inline). You need to specify the Content Type too, and you may want to add the file name and length (to help the browser drawing a realistic progressbar).

For example, when downloading a ZIP:

response.setContentType("application/zip");
response.addHeader("Content-Disposition", 
                   "attachment; filename=\"name of my file.zip\"");
response.setHeader("Content-Length", myFile.length()); // or myByte[].length...

With Struts2 (unless you are using the Action as a Servlet, an hack for direct streaming, for example), you don't need to directly write anything to the response; simply using the Stream result type and configuring it in struts.xml will work: EXAMPLE

<result name="success" type="stream">
   <param name="contentType">application/zip</param>
   <param name="contentDisposition">attachment;filename="${fileName}"</param>
   <param name="contentLength">${fileLength}</param>
</result>

3. Framework agnostic (/ Struts2 framework): Servlet(/Action) opening file inside the browser

If you want to open the file inside the browser, instead of downloading it, the Content-disposition must be set to inline, but the target can't be the current window location; you must target a new window created by javascript, an <iframe> in the page, or a new window created on-the-fly with the "discussed" target="_blank":

<!-- From a parent page into an IFrame without javascript -->   
<a href="downloadServlet?param1=value1" target="iFrameName">
    download
</a>

<!-- In a new window without javascript --> 
<a href="downloadServlet?param1=value1" target="_blank">
    download
</a>

<!-- In a new window with javascript -->    
<a href="javascript:window.open('downloadServlet?param1=value1');" >
    download
</a>

How to see if a directory exists or not in Perl?

Use -d (full list of file tests)

if (-d "cgi-bin") {
    # directory called cgi-bin exists
}
elsif (-e "cgi-bin") {
    # cgi-bin exists but is not a directory
}
else {
    # nothing called cgi-bin exists
}

As a note, -e doesn't distinguish between files and directories. To check if something exists and is a plain file, use -f.

How to set different colors in HTML in one statement?

Use the span tag

<style>
    .redText
    {
        color:red;
    }
    .blackText
    {
        color:black;
        font-weight:bold;
    }
</style>

<span class="redText">My Name is:</span>&nbsp;<span class="blackText">Tintincute</span>

It's also a good idea to avoid inline styling. Use a custom CSS class instead.

The source was not found, but some or all event logs could not be searched

Launch Developer command line "As an Administrator". This account has full access to Security log

Android Fatal signal 11 (SIGSEGV) at 0x636f7d89 (code=1). How can it be tracked down?

I also got this error many times and I solved it. This error will be faced in case of memory management in native side.

Your application is accessing memory outside of its address space. This is most likely an invalid pointer access. SIGSEGV = segmentation fault in native code. Since it is not occurring in Java code you won't see a stack trace with details. However, you may still see some stack trace information in the logcat if you look around a bit after the application process crashes. It will not tell you the line number within the file, but will tell you which object files and addresses were in use in the call chain. From there you can often figure out which area of the code is problematic. You can also setup a gdb native connection to the target process and catch it in the debugger.

Best practice to call ConfigureAwait for all server-side code

Brief answer to your question: No. You shouldn't call ConfigureAwait(false) at the application level like that.

TL;DR version of the long answer: If you are writing a library where you don't know your consumer and don't need a synchronization context (which you shouldn't in a library I believe), you should always use ConfigureAwait(false). Otherwise, the consumers of your library may face deadlocks by consuming your asynchronous methods in a blocking fashion. This depends on the situation.

Here is a bit more detailed explanation on the importance of ConfigureAwait method (a quote from my blog post):

When you are awaiting on a method with await keyword, compiler generates bunch of code in behalf of you. One of the purposes of this action is to handle synchronization with the UI (or main) thread. The key component of this feature is the SynchronizationContext.Current which gets the synchronization context for the current thread. SynchronizationContext.Current is populated depending on the environment you are in. The GetAwaiter method of Task looks up for SynchronizationContext.Current. If current synchronization context is not null, the continuation that gets passed to that awaiter will get posted back to that synchronization context.

When consuming a method, which uses the new asynchronous language features, in a blocking fashion, you will end up with a deadlock if you have an available SynchronizationContext. When you are consuming such methods in a blocking fashion (waiting on the Task with Wait method or taking the result directly from the Result property of the Task), you will block the main thread at the same time. When eventually the Task completes inside that method in the threadpool, it is going to invoke the continuation to post back to the main thread because SynchronizationContext.Current is available and captured. But there is a problem here: the UI thread is blocked and you have a deadlock!

Also, here are two great articles for you which are exactly for your question:

Finally, there is a great short video from Lucian Wischik exactly on this topic: Async library methods should consider using Task.ConfigureAwait(false).

Hope this helps.

Logical operators for boolean indexing in Pandas

TLDR; Logical Operators in Pandas are &, | and ~, and parentheses (...) is important!

Python's and, or and not logical operators are designed to work with scalars. So Pandas had to do one better and override the bitwise operators to achieve vectorized (element-wise) version of this functionality.

So the following in python (exp1 and exp2 are expressions which evaluate to a boolean result)...

exp1 and exp2              # Logical AND
exp1 or exp2               # Logical OR
not exp1                   # Logical NOT

...will translate to...

exp1 & exp2                # Element-wise logical AND
exp1 | exp2                # Element-wise logical OR
~exp1                      # Element-wise logical NOT

for pandas.

If in the process of performing logical operation you get a ValueError, then you need to use parentheses for grouping:

(exp1) op (exp2)

For example,

(df['col1'] == x) & (df['col2'] == y) 

And so on.


Boolean Indexing: A common operation is to compute boolean masks through logical conditions to filter the data. Pandas provides three operators: & for logical AND, | for logical OR, and ~ for logical NOT.

Consider the following setup:

np.random.seed(0)
df = pd.DataFrame(np.random.choice(10, (5, 3)), columns=list('ABC'))
df

   A  B  C
0  5  0  3
1  3  7  9
2  3  5  2
3  4  7  6
4  8  8  1

Logical AND

For df above, say you'd like to return all rows where A < 5 and B > 5. This is done by computing masks for each condition separately, and ANDing them.

Overloaded Bitwise & Operator
Before continuing, please take note of this particular excerpt of the docs, which state

Another common operation is the use of boolean vectors to filter the data. The operators are: | for or, & for and, and ~ for not. These must be grouped by using parentheses, since by default Python will evaluate an expression such as df.A > 2 & df.B < 3 as df.A > (2 & df.B) < 3, while the desired evaluation order is (df.A > 2) & (df.B < 3).

So, with this in mind, element wise logical AND can be implemented with the bitwise operator &:

df['A'] < 5

0    False
1     True
2     True
3     True
4    False
Name: A, dtype: bool

df['B'] > 5

0    False
1     True
2    False
3     True
4     True
Name: B, dtype: bool

(df['A'] < 5) & (df['B'] > 5)

0    False
1     True
2    False
3     True
4    False
dtype: bool

And the subsequent filtering step is simply,

df[(df['A'] < 5) & (df['B'] > 5)]

   A  B  C
1  3  7  9
3  4  7  6

The parentheses are used to override the default precedence order of bitwise operators, which have higher precedence over the conditional operators < and >. See the section of Operator Precedence in the python docs.

If you do not use parentheses, the expression is evaluated incorrectly. For example, if you accidentally attempt something such as

df['A'] < 5 & df['B'] > 5

It is parsed as

df['A'] < (5 & df['B']) > 5

Which becomes,

df['A'] < something_you_dont_want > 5

Which becomes (see the python docs on chained operator comparison),

(df['A'] < something_you_dont_want) and (something_you_dont_want > 5)

Which becomes,

# Both operands are Series...
something_else_you_dont_want1 and something_else_you_dont_want2

Which throws

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

So, don't make that mistake!1

Avoiding Parentheses Grouping
The fix is actually quite simple. Most operators have a corresponding bound method for DataFrames. If the individual masks are built up using functions instead of conditional operators, you will no longer need to group by parens to specify evaluation order:

df['A'].lt(5)

0     True
1     True
2     True
3     True
4    False
Name: A, dtype: bool

df['B'].gt(5)

0    False
1     True
2    False
3     True
4     True
Name: B, dtype: bool

df['A'].lt(5) & df['B'].gt(5)

0    False
1     True
2    False
3     True
4    False
dtype: bool

See the section on Flexible Comparisons.. To summarise, we have

+------------------------------+
¦    ¦ Operator   ¦ Function   ¦
¦----+------------+------------¦
¦  0 ¦ >          ¦ gt         ¦
+----+------------+------------¦
¦  1 ¦ >=         ¦ ge         ¦
+----+------------+------------¦
¦  2 ¦ <          ¦ lt         ¦
+----+------------+------------¦
¦  3 ¦ <=         ¦ le         ¦
+----+------------+------------¦
¦  4 ¦ ==         ¦ eq         ¦
+----+------------+------------¦
¦  5 ¦ !=         ¦ ne         ¦
+------------------------------+

Another option for avoiding parentheses is to use DataFrame.query (or eval):

df.query('A < 5 and B > 5')

   A  B  C
1  3  7  9
3  4  7  6

I have extensively documented query and eval in Dynamic Expression Evaluation in pandas using pd.eval().

operator.and_
Allows you to perform this operation in a functional manner. Internally calls Series.__and__ which corresponds to the bitwise operator.

import operator 

operator.and_(df['A'] < 5, df['B'] > 5)
# Same as,
# (df['A'] < 5).__and__(df['B'] > 5) 

0    False
1     True
2    False
3     True
4    False
dtype: bool

df[operator.and_(df['A'] < 5, df['B'] > 5)]

   A  B  C
1  3  7  9
3  4  7  6

You won't usually need this, but it is useful to know.

Generalizing: np.logical_and (and logical_and.reduce)
Another alternative is using np.logical_and, which also does not need parentheses grouping:

np.logical_and(df['A'] < 5, df['B'] > 5)

0    False
1     True
2    False
3     True
4    False
Name: A, dtype: bool

df[np.logical_and(df['A'] < 5, df['B'] > 5)]

   A  B  C
1  3  7  9
3  4  7  6

np.logical_and is a ufunc (Universal Functions), and most ufuncs have a reduce method. This means it is easier to generalise with logical_and if you have multiple masks to AND. For example, to AND masks m1 and m2 and m3 with &, you would have to do

m1 & m2 & m3

However, an easier option is

np.logical_and.reduce([m1, m2, m3])

This is powerful, because it lets you build on top of this with more complex logic (for example, dynamically generating masks in a list comprehension and adding all of them):

import operator

cols = ['A', 'B']
ops = [np.less, np.greater]
values = [5, 5]

m = np.logical_and.reduce([op(df[c], v) for op, c, v in zip(ops, cols, values)])
m 
# array([False,  True, False,  True, False])

df[m]
   A  B  C
1  3  7  9
3  4  7  6

1 - I know I'm harping on this point, but please bear with me. This is a very, very common beginner's mistake, and must be explained very thoroughly.


Logical OR

For the df above, say you'd like to return all rows where A == 3 or B == 7.

Overloaded Bitwise |

df['A'] == 3

0    False
1     True
2     True
3    False
4    False
Name: A, dtype: bool

df['B'] == 7

0    False
1     True
2    False
3     True
4    False
Name: B, dtype: bool

(df['A'] == 3) | (df['B'] == 7)

0    False
1     True
2     True
3     True
4    False
dtype: bool

df[(df['A'] == 3) | (df['B'] == 7)]

   A  B  C
1  3  7  9
2  3  5  2
3  4  7  6

If you haven't yet, please also read the section on Logical AND above, all caveats apply here.

Alternatively, this operation can be specified with

df[df['A'].eq(3) | df['B'].eq(7)]

   A  B  C
1  3  7  9
2  3  5  2
3  4  7  6

operator.or_
Calls Series.__or__ under the hood.

operator.or_(df['A'] == 3, df['B'] == 7)
# Same as,
# (df['A'] == 3).__or__(df['B'] == 7)

0    False
1     True
2     True
3     True
4    False
dtype: bool

df[operator.or_(df['A'] == 3, df['B'] == 7)]

   A  B  C
1  3  7  9
2  3  5  2
3  4  7  6

np.logical_or
For two conditions, use logical_or:

np.logical_or(df['A'] == 3, df['B'] == 7)

0    False
1     True
2     True
3     True
4    False
Name: A, dtype: bool

df[np.logical_or(df['A'] == 3, df['B'] == 7)]

   A  B  C
1  3  7  9
2  3  5  2
3  4  7  6

For multiple masks, use logical_or.reduce:

np.logical_or.reduce([df['A'] == 3, df['B'] == 7])
# array([False,  True,  True,  True, False])

df[np.logical_or.reduce([df['A'] == 3, df['B'] == 7])]

   A  B  C
1  3  7  9
2  3  5  2
3  4  7  6

Logical NOT

Given a mask, such as

mask = pd.Series([True, True, False])

If you need to invert every boolean value (so that the end result is [False, False, True]), then you can use any of the methods below.

Bitwise ~

~mask

0    False
1    False
2     True
dtype: bool

Again, expressions need to be parenthesised.

~(df['A'] == 3)

0     True
1    False
2    False
3     True
4     True
Name: A, dtype: bool

This internally calls

mask.__invert__()

0    False
1    False
2     True
dtype: bool

But don't use it directly.

operator.inv
Internally calls __invert__ on the Series.

operator.inv(mask)

0    False
1    False
2     True
dtype: bool

np.logical_not
This is the numpy variant.

np.logical_not(mask)

0    False
1    False
2     True
dtype: bool

Note, np.logical_and can be substituted for np.bitwise_and, logical_or with bitwise_or, and logical_not with invert.

What is a stack trace, and how can I use it to debug my application errors?

In simple terms, a stack trace is a list of the method calls that the application was in the middle of when an Exception was thrown.

Simple Example

With the example given in the question, we can determine exactly where the exception was thrown in the application. Let's have a look at the stack trace:

Exception in thread "main" java.lang.NullPointerException
        at com.example.myproject.Book.getTitle(Book.java:16)
        at com.example.myproject.Author.getBookTitles(Author.java:25)
        at com.example.myproject.Bootstrap.main(Bootstrap.java:14)

This is a very simple stack trace. If we start at the beginning of the list of "at ...", we can tell where our error happened. What we're looking for is the topmost method call that is part of our application. In this case, it's:

at com.example.myproject.Book.getTitle(Book.java:16)

To debug this, we can open up Book.java and look at line 16, which is:

15   public String getTitle() {
16      System.out.println(title.toString());
17      return title;
18   }

This would indicate that something (probably title) is null in the above code.

Example with a chain of exceptions

Sometimes applications will catch an Exception and re-throw it as the cause of another Exception. This typically looks like:

34   public void getBookIds(int id) {
35      try {
36         book.getId(id);    // this method it throws a NullPointerException on line 22
37      } catch (NullPointerException e) {
38         throw new IllegalStateException("A book has a null property", e)
39      }
40   }

This might give you a stack trace that looks like:

Exception in thread "main" java.lang.IllegalStateException: A book has a null property
        at com.example.myproject.Author.getBookIds(Author.java:38)
        at com.example.myproject.Bootstrap.main(Bootstrap.java:14)
Caused by: java.lang.NullPointerException
        at com.example.myproject.Book.getId(Book.java:22)
        at com.example.myproject.Author.getBookIds(Author.java:36)
        ... 1 more

What's different about this one is the "Caused by". Sometimes exceptions will have multiple "Caused by" sections. For these, you typically want to find the "root cause", which will be one of the lowest "Caused by" sections in the stack trace. In our case, it's:

Caused by: java.lang.NullPointerException <-- root cause
        at com.example.myproject.Book.getId(Book.java:22) <-- important line

Again, with this exception we'd want to look at line 22 of Book.java to see what might cause the NullPointerException here.

More daunting example with library code

Usually stack traces are much more complex than the two examples above. Here's an example (it's a long one, but demonstrates several levels of chained exceptions):

javax.servlet.ServletException: Something bad happened
    at com.example.myproject.OpenSessionInViewFilter.doFilter(OpenSessionInViewFilter.java:60)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.example.myproject.ExceptionHandlerFilter.doFilter(ExceptionHandlerFilter.java:28)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.example.myproject.OutputBufferFilter.doFilter(OutputBufferFilter.java:33)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:943)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:756)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.jetty.bio.SocketConnector$Connection.run(SocketConnector.java:228)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: com.example.myproject.MyProjectServletException
    at com.example.myproject.MyServlet.doPost(MyServlet.java:169)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.example.myproject.OpenSessionInViewFilter.doFilter(OpenSessionInViewFilter.java:30)
    ... 27 more
Caused by: org.hibernate.exception.ConstraintViolationException: could not insert: [com.example.myproject.MyEntity]
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96)
    at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
    at org.hibernate.id.insert.AbstractSelectingDelegate.performInsert(AbstractSelectingDelegate.java:64)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2329)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2822)
    at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
    at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:268)
    at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:321)
    at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
    at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
    at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:56)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
    at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:50)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
    at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:705)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:693)
    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:689)
    at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344)
    at $Proxy19.save(Unknown Source)
    at com.example.myproject.MyEntityService.save(MyEntityService.java:59) <-- relevant call (see notes below)
    at com.example.myproject.MyServlet.doPost(MyServlet.java:164)
    ... 32 more
Caused by: java.sql.SQLException: Violation of unique constraint MY_ENTITY_UK_1: duplicate value(s) for column(s) MY_COLUMN in statement [...]
    at org.hsqldb.jdbc.Util.throwError(Unknown Source)
    at org.hsqldb.jdbc.jdbcPreparedStatement.executeUpdate(Unknown Source)
    at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeUpdate(NewProxyPreparedStatement.java:105)
    at org.hibernate.id.insert.AbstractSelectingDelegate.performInsert(AbstractSelectingDelegate.java:57)
    ... 54 more

In this example, there's a lot more. What we're mostly concerned about is looking for methods that are from our code, which would be anything in the com.example.myproject package. From the second example (above), we'd first want to look down for the root cause, which is:

Caused by: java.sql.SQLException

However, all the method calls under that are library code. So we'll move up to the "Caused by" above it, and look for the first method call originating from our code, which is:

at com.example.myproject.MyEntityService.save(MyEntityService.java:59)

Like in previous examples, we should look at MyEntityService.java on line 59, because that's where this error originated (this one's a bit obvious what went wrong, since the SQLException states the error, but the debugging procedure is what we're after).

Setting HTTP headers

All of the above answers are wrong because they fail to handle the OPTIONS preflight request, the solution is to override the mux router's interface. See AngularJS $http get request failed with custom header (alllowed in CORS)

func main() {
    r := mux.NewRouter()
    r.HandleFunc("/save", saveHandler)
    http.Handle("/", &MyServer{r})
    http.ListenAndServe(":8080", nil);

}

type MyServer struct {
    r *mux.Router
}

func (s *MyServer) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
    if origin := req.Header.Get("Origin"); origin != "" {
        rw.Header().Set("Access-Control-Allow-Origin", origin)
        rw.Header().Set("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE")
        rw.Header().Set("Access-Control-Allow-Headers",
            "Accept, Content-Type, Content-Length, Accept-Encoding, X-CSRF-Token, Authorization")
    }
    // Stop here if its Preflighted OPTIONS request
    if req.Method == "OPTIONS" {
        return
    }
    // Lets Gorilla work
    s.r.ServeHTTP(rw, req)
}

CASE statement in SQLite query

Also, you do not have to use nested CASEs. You can use several WHEN-THEN lines and the ELSE line is also optional eventhough I recomend it

CASE 
   WHEN [condition.1] THEN [expression.1]
   WHEN [condition.2] THEN [expression.2]
   ...
   WHEN [condition.n] THEN [expression.n]
   ELSE [expression] 
END

How to develop Android app completely using python?

There are two primary contenders for python apps on Android

Chaquopy

https://chaquo.com/chaquopy/

This integrates with the Android build system, it provides a Python API for all android features. To quote the site "The complete Android API and user interface toolkit are directly at your disposal."

Beeware (Toga widget toolkit)

https://pybee.org/

This provides a multi target transpiler, supports many targets such as Android and iOS. It uses a generic widget toolkit (toga) that maps to the host interface calls.

Which One?

Both are active projects and their github accounts shows a fair amount of recent activity.

Beeware Toga like all widget libraries is good for getting the basics out to multiple platforms. If you have basic designs, and a desire to expand to other platforms this should work out well for you.

On the other hand, Chaquopy is a much more precise in its mapping of the python API to Android. It also allows you to mix in Java, useful if you want to use existing code from other resources. If you have strict design targets, and predominantly want to target Android this is a much better resource.

How to define constants in ReactJS

You don't need to use anything but plain React and ES6 to achieve what you want. As per Jim's answer, just define the constant in the right place. I like the idea of keeping the constant local to the component if not needed externally. The below is an example of possible usage.

import React from "react";

const sizeToLetterMap = {
  small_square: 's',
  large_square: 'q',
  thumbnail: 't',
  small_240: 'm',
  small_320: 'n',
  medium_640: 'z',
  medium_800: 'c',
  large_1024: 'b',
  large_1600: 'h',
  large_2048: 'k',
  original: 'o'
};

class PhotoComponent extends React.Component {
  constructor(args) {
    super(args);
  }

  photoUrl(image, size_text) {
    return (<span>
      Image: {image}, Size Letter: {sizeToLetterMap[size_text]}
    </span>);
  }

  render() {
    return (
      <div className="photo-wrapper">
        The url is: {this.photoUrl(this.props.image, this.props.size_text)}
      </div>
    )
  }
}

export default PhotoComponent;

// Call this with <PhotoComponent image="abc.png" size_text="thumbnail" />
// Of course the component must first be imported where used, example:
// import PhotoComponent from "./photo_component.jsx";

Get the system date and split day, month and year

You should use DateTime.TryParseExcact if you know the format, or if not and want to use the system settings DateTime.TryParse. And to print the date,DateTime.ToString with the right format in the argument. To get the year, month or day you have DateTime.Year, DateTime.Month or DateTime.Day.

See DateTime Structures in MSDN for additional references.

How can I add or update a query string parameter?

This answer is just a small tweak of ellemayo's answer. It will automatically update the URL instead of just returning the updated string.

function _updateQueryString(key, value, url) {
    if (!url) url = window.location.href;

    let updated = ''
    var re = new RegExp("([?&])" + key + "=.*?(&|#|$)(.*)", "gi"),
        hash;

    if (re.test(url)) {
        if (typeof value !== 'undefined' && value !== null) {
            updated = url.replace(re, '$1' + key + "=" + value + '$2$3');
        } 
        else {
            hash = url.split('#');
            url = hash[0].replace(re, '$1$3').replace(/(&|\?)$/, '');
            if (typeof hash[1] !== 'undefined' && hash[1] !== null) {
                url += '#' + hash[1];
            }
            updated = url;
        }
    }
    else {
        if (typeof value !== 'undefined' && value !== null) {
            var separator = url.indexOf('?') !== -1 ? '&' : '?';
            hash = url.split('#');
            url = hash[0] + separator + key + '=' + value;
            if (typeof hash[1] !== 'undefined' && hash[1] !== null) {
                url += '#' + hash[1];
            }
            updated = url;
        }
        else {
            updated = url;
        }
    }

    window.history.replaceState({ path: updated }, '', updated);
}

How to refresh materialized view in oracle

a bit late to the game, but I found a way to make the original syntax in this question work (I'm on Oracle 11g)

** first switch to schema of your MV **

EXECUTE DBMS_MVIEW.REFRESH(LIST=>'MV_MY_VIEW');

alternatively you can add some options:

EXECUTE DBMS_MVIEW.REFRESH(LIST=>'MV_MY_VIEW',PARALLELISM=>4);

this actually works for me, and adding parallelism option sped my execution about 2.5 times.

More info here: How to Refresh a Materialized View in Parallel

jQuery $.cookie is not a function

Check that you included the script in header and not in footer of the page. Particularly in WordPress this one didn't work:

wp_register_script('cookie', get_template_directory_uri() . '/js/jquery.cookie.js', array(), false, true);

The last parameter indicates including the script in footer and needed to be changed to false (default). The way it worked:

wp_register_script('cookie', get_template_directory_uri() . '/js/jquery.cookie.js');

What to do about Eclipse's "No repository found containing: ..." error messages?

Some of the above solutions worked to resolve some of my errors... it seems that after a while update connections just get corrupted and there is no silver-bullet. Managing updates through the marketplace (Help > Marketplace > 'show updates') allowed me to narrow down the packages with failed dependencies.

Here's what I tried (taken from posts above):

  1. switching https to http for software sites
  2. running Eclipse as administrator
  3. 'disabling' obviously outdated software sites
  4. 'enabling' all software sites
  5. adding backslashes to the end of software site urls
  6. uninstalling and re-installing troublesome software

I was still left with some Mylyn wikitext errors despite trying the suggestions here

Eclipse IDE for JavaScript and Web Developers

Version: 2019-09 R (4.13.0) Build id: 20190917-1200

assign value using linq

Be aware that it only updates the first company it found with company id 1. For multiple

 (from c in listOfCompany where c.id == 1 select c).First().Name = "Whatever Name";

For Multiple updates

 from c in listOfCompany where c.id == 1 select c => {c.Name = "Whatever Name";  return c;}

how to empty recyclebin through command prompt?

You can effectively "empty" the Recycle Bin from the command line by permanently deleting the Recycle Bin directory on the drive that contains the system files. (In most cases, this will be the C: drive, but you shouldn't hardcode that value because it won't always be true. Instead, use the %systemdrive% environment variable.)

The reason that this tactic works is because each drive has a hidden, protected folder with the name $Recycle.bin, which is where the Recycle Bin actually stores the deleted files and folders. When this directory is deleted, Windows automatically creates a new directory.

So, to remove the directory, use the rd command (r?emove d?irectory) with the /s parameter, which indicates that all of the files and directories within the specified directory should be removed as well:

rd /s %systemdrive%\$Recycle.bin

Do note that this action will permanently delete all files and folders currently in the Recycle Bin from all user accounts. Additionally, you will (obviously) have to run the command from an elevated command prompt in order to have sufficient privileges to perform this action.

Running multiple commands in one line in shell

Note that cp A B; rm A is exactly mv A B. It'll be faster too, as you don't have to actually copy the bytes (assuming the destination is on the same filesystem), just rename the file. So you want cp A B; mv A C

css h1 - only as wide as the text

align-self-start, align-self-center... in flexbox

.centercol h1{
    background: #F2EFE9;
    border-left: 3px solid #C6C1B8;
    color: #006BB6;
    display: block;
    align-self: center;
    font-weight: normal;
    font-size: 18px;
    padding: 3px 3px 3px 6px;
}

How to wait until an element is present in Selenium?

You need to call ignoring with exception to ignore while the WebDriver will wait.

FluentWait<WebDriver> fluentWait = new FluentWait<>(driver)
        .withTimeout(30, TimeUnit.SECONDS)
        .pollingEvery(200, TimeUnit.MILLISECONDS)
        .ignoring(NoSuchElementException.class);

See the documentation of FluentWait for more info. But beware that this condition is already implemented in ExpectedConditions so you should use

WebElement element = (new WebDriverWait(driver, 10))
   .until(ExpectedConditions.elementToBeClickable(By.id("someid")));

*Update for newer versions of Selenium:

withTimeout(long, TimeUnit) has become withTimeout(Duration)
pollingEvery(long, TimeUnit) has become pollingEvery(Duration)

So the code will look as such:

FluentWait<WebDriver> fluentWait = new FluentWait<>(driver)
        .withTimeout(Duration.ofSeconds(30)
        .pollingEvery(Duration.ofMillis(200)
        .ignoring(NoSuchElementException.class);

Basic tutorial for waiting can be found here.

How to change an input button image using CSS?

A variation on the previous answers. I found that opacity needs to be set, of course this will work in IE6 and on. There was a problem with the line-height solution in IE8 where the button would not respond. And with this you get a hand cursor as well!

<div id="myButton">
  <input id="myInputButton" type="submit" name="" value="">
</div>

#myButton {
 background: url("form_send_button.gif") no-repeat;
 width: 62px;
 height: 24px;
 }

#myInputButton { 
 background: url("form_send_button.gif") no-repeat;
 opacity: 0;
 -ms-filter:"progid:DXImageTransform.Microsoft.Alpha(Opacity=0)";
 filter: alpha(opacity=0);
 width: 67px;
 height: 26px;
 cursor: pointer;
 cursor: hand;
}

Encode URL in JavaScript?

To encode a URL, as has been said before, you have two functions:

encodeURI()

and

encodeURIComponent()

The reason both exist is that the first preserves the URL with the risk of leaving too many things unescaped, while the second encodes everything needed.

With the first, you could copy the newly escaped URL into address bar (for example) and it would work. However your unescaped '&'s would interfere with field delimiters, the '='s would interfere with field names and values, and the '+'s would look like spaces. But for simple data when you want to preserve the URL nature of what you are escaping, this works.

The second is everything you need to do to make sure nothing in your string interfers with a URL. It leaves various unimportant characters unescaped so that the URL remains as human readable as possible without interference. A URL encoded this way will no longer work as a URL without unescaping it.

So if you can take the time, you always want to use encodeURIComponent() -- before adding on name/value pairs encode both the name and the value using this function before adding it to the query string.

I'm having a tough time coming up with reasons to use the encodeURI() -- I'll leave that to the smarter people.

Rails select helper - Default selected value, how?

I couldn't get this to work and found that I needed to add the "selected" html attribute not only to the correct <option> tag but also to the <select> tag. MDN's docs on the selected attribute of the select tag say:

selected - Boolean attribute indicates that a specific option can be initially selected.

That means the code should look like:

f.select :project_id, options_for_select(@project_select, default_val), html: {selected: true}

git remote prune – didn't show as many pruned branches as I expected

When you use git push origin :staleStuff, it automatically removes origin/staleStuff, so when you ran git remote prune origin, you have pruned some branch that was removed by someone else. It's more likely that your co-workers now need to run git prune to get rid of branches you have removed.


So what exactly git remote prune does? Main idea: local branches (not tracking branches) are not touched by git remote prune command and should be removed manually.

Now, a real-world example for better understanding:

You have a remote repository with 2 branches: master and feature. Let's assume that you are working on both branches, so as a result you have these references in your local repository (full reference names are given to avoid any confusion):

  • refs/heads/master (short name master)
  • refs/heads/feature (short name feature)
  • refs/remotes/origin/master (short name origin/master)
  • refs/remotes/origin/feature (short name origin/feature)

Now, a typical scenario:

  1. Some other developer finishes all work on the feature, merges it into master and removes feature branch from remote repository.
  2. By default, when you do git fetch (or git pull), no references are removed from your local repository, so you still have all those 4 references.
  3. You decide to clean them up, and run git remote prune origin.
  4. git detects that feature branch no longer exists, so refs/remotes/origin/feature is a stale branch which should be removed.
  5. Now you have 3 references, including refs/heads/feature, because git remote prune does not remove any refs/heads/* references.

It is possible to identify local branches, associated with remote tracking branches, by branch.<branch_name>.merge configuration parameter. This parameter is not really required for anything to work (probably except git pull), so it might be missing.

(updated with example & useful info from comments)

Converting string to double in C#

You can try this example out. A simple C# progaram to convert string to double

class Calculations{

protected double length;
protected double height;
protected double width;

public void get_data(){

this.length = Convert.ToDouble(Console.ReadLine());
this.width  = Convert.ToDouble(Console.ReadLine());
this.height = Convert.ToDouble(Console.ReadLine());

   }
}

Accessing elements of Python dictionary by index

mydict = {
'Apple': {'American':'16', 'Mexican':10, 'Chinese':5},
'Grapes':{'Arabian':'25','Indian':'20'} }

for n in mydict:
    print(mydict[n])

iPhone SDK on Windows (alternative solutions)

I looked into this before buying a Mac Mini. The answer is, essentially, no. You pretty much have to buy a Leopard Mac to do iPhone SDK development for apps that run on non-jailbroken iPhones.

Not that it's 100% impossible, but it's 99.99% unreasonable. Like changing light bulbs with your feet.

Not only do you have to be in Xcode, but you have to get certificates into the Keychain manager to be able to have Xcode and the iPhone communicate. And you have to set all kinds of setting in Xcode just right.

undefined reference to `std::ios_base::Init::Init()'

You can resolve this in several ways:

  • Use g++ in stead of gcc: g++ -g -o MatSim MatSim.cpp
  • Add -lstdc++: gcc -g -o MatSim MatSim.cpp -lstdc++
  • Replace <string.h> by <string>

This is a linker problem, not a compiler issue. The same problem is covered in the question iostream linker error – it explains what is going on.

Difference between Visibility.Collapsed and Visibility.Hidden

The difference is that Visibility.Hidden hides the control, but reserves the space it occupies in the layout. So it renders whitespace instead of the control. Visibilty.Collapsed does not render the control and does not reserve the whitespace. The space the control would take is 'collapsed', hence the name.

The exact text from the MSDN:

Collapsed: Do not display the element, and do not reserve space for it in layout.

Hidden: Do not display the element, but reserve space for the element in layout.

Visible: Display the element.

See: http://msdn.microsoft.com/en-us/library/system.windows.visibility.aspx

Why is there no xrange function in Python3?

comp:~$ python Python 2.7.6 (default, Jun 22 2015, 17:58:13) [GCC 4.8.2] on linux2

>>> import timeit
>>> timeit.timeit("[x for x in xrange(1000000) if x%4]",number=100)

5.656799077987671

>>> timeit.timeit("[x for x in xrange(1000000) if x%4]",number=100)

5.579368829727173

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=100)

21.54827117919922

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=100)

22.014557123184204

With timeit number=1 param:

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=1)

0.2245171070098877

>>> timeit.timeit("[x for x in xrange(1000000) if x%4]",number=1)

0.10750913619995117

comp:~$ python3 Python 3.4.3 (default, Oct 14 2015, 20:28:29) [GCC 4.8.4] on linux

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=100)

9.113872020003328

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=100)

9.07014398300089

With timeit number=1,2,3,4 param works quick and in linear way:

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=1)

0.09329321900440846

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=2)

0.18501482300052885

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=3)

0.2703447980020428

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=4)

0.36209142999723554

So it seems if we measure 1 running loop cycle like timeit.timeit("[x for x in range(1000000) if x%4]",number=1) (as we actually use in real code) python3 works quick enough, but in repeated loops python 2 xrange() wins in speed against range() from python 3.

Make a div fill the height of the remaining screen space

There really isn't a sound, cross-browser way to do this in CSS. Assuming your layout has complexities, you need to use JavaScript to set the element's height. The essence of what you need to do is:

Element Height = Viewport height - element.offset.top - desired bottom margin

Once you can get this value and set the element's height, you need to attach event handlers to both the window onload and onresize so that you can fire your resize function.

Also, assuming your content could be larger than the viewport, you will need to set overflow-y to scroll.

Configure Nginx with proxy_pass

Nginx prefers prefix-based location matches (not involving regular expression), that's why in your code block, /stash redirects are going to /.

The algorithm used by Nginx to select which location to use is described thoroughly here: https://www.digitalocean.com/community/tutorials/understanding-nginx-server-and-location-block-selection-algorithms#matching-location-blocks

How to create a fixed sidebar layout with Bootstrap 4?

I'm using the J.S. to fix a sidebar menu. I've tried a lot of solutions with CSS but it's the simplest way to solve it, just add J.S. adding and removing a native BootStrap class: "position-fixed".

The J.S.:

var lateral = false;
function fixar() {

            var element, name, arr;
            element = document.getElementById("minhasidebar");

            if (lateral) {
                element.className = element.className.replace(
                        /\bposition-fixed\b/g, "");
                lateral = false;
            } else {

                name = "position-fixed";
                arr = element.className.split(" ");
                if (arr.indexOf(name) == -1) {
                    element.className += " " + name;
                }
                lateral = true;
            }

        }

The HTML:

Sidebar:

<aside>
        <nav class="sidebar ">
             <div id="minhasidebar">
                 <ul class="nav nav-pills">
                     <li class="nav-item"><a class="nav-link active" 
                     th:href="@{/hoje/inicial}"> <i class="oi oi-clipboard"></i> 
                     <span>Hoje</span>
                     </a></li>
                 </ul>
             </div>
        </nav>            
</aside>

How to add icons to React Native app

I would use a service to scale the icon correctly. http://makeappicon.com/ seems good. Use a image on the larger size as scaling up a smaller image can lead to the larger icons being pixelated. That site will give you sizes for both iOS and Android.

From there its just a matter of setting the icon like you would a regular native app.

https://help.apple.com/xcode/mac/8.0/#/dev10510b1f7

Set icon for Android application

Difference between wait and sleep

You are correct - Sleep() causes that thread to "sleep" and the CPU will go off and process other threads (otherwise known as context switching) wheras I believe Wait keeps the CPU processing the current thread.

We have both because although it may seem sensible to let other people use the CPU while you're not using it, actualy there is an overhead to context switching - depending on how long the sleep is for, it can be more expensive in CPU cycles to switch threads than it is to simply have your thread doing nothing for a few ms.

Also note that sleep forces a context switch.

Also - in general it's not possible to control context switching - during the Wait the OS may (and will for longer waits) choose to process other threads.

/lib/ld-linux.so.2: bad ELF interpreter: No such file or directory

You did not mention what the command was that you were trying to run that produced the error message. However, the bottom line problem is that you are trying to run and/or install 32-bit (i686) packages on a 64-bit (x86_64) system which is not a good idea. For example, if you were trying to run the 32-bit version of Perl on a 64-bit system, the result would be something like

perl: /lib/ld-linux.so.2: bad ELF interpreter: No such file or directory

If you still want to use the rpm command to install the 32-bit versions of glibc and glibc-common on your system, then you need to know that you must install both of the packages at the same time and as a single command because they are dependencies of each other. The command to run in your case would be:

rpm -Uvh glibc-2.12-1.80.el6.i686.rpm glibc-common-2.12-1.80.el6.i686.rpm

Why does LayoutInflater ignore the layout_width and layout_height layout parameters I've specified?

I've investigated this issue, referring to the LayoutInflater docs and setting up a small sample demonstration project. The following tutorials shows how to dynamically populate a layout using LayoutInflater.

Before we get started see what LayoutInflater.inflate() parameters look like:

  • resource: ID for an XML layout resource to load (e.g., R.layout.main_page)
  • root: Optional view to be the parent of the generated hierarchy (if attachToRoot is true), or else simply an object that provides a set of LayoutParams values for root of the returned hierarchy (if attachToRoot is false.)
  • attachToRoot: Whether the inflated hierarchy should be attached to the root parameter? If false, root is only used to create the correct subclass of LayoutParams for the root view in the XML.

  • Returns: The root View of the inflated hierarchy. If root was supplied and attachToRoot is true, this is root; otherwise it is the root of the inflated XML file.

Now for the sample layout and code.

Main layout (main.xml):

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
</LinearLayout>

Added into this container is a separate TextView, visible as small red square if layout parameters are successfully applied from XML (red.xml):

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="25dp"
    android:layout_height="25dp"
    android:background="#ff0000"
    android:text="red" />

Now LayoutInflater is used with several variations of call parameters

public class InflaterTest extends Activity {

    private View view;

    @Override
    public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);

      setContentView(R.layout.main);
      ViewGroup parent = (ViewGroup) findViewById(R.id.container);

      // result: layout_height=wrap_content layout_width=match_parent
      view = LayoutInflater.from(this).inflate(R.layout.red, null);
      parent.addView(view);

      // result: layout_height=100 layout_width=100
      view = LayoutInflater.from(this).inflate(R.layout.red, null);
      parent.addView(view, 100, 100);

      // result: layout_height=25dp layout_width=25dp
      // view=textView due to attachRoot=false
      view = LayoutInflater.from(this).inflate(R.layout.red, parent, false);
      parent.addView(view);

      // result: layout_height=25dp layout_width=25dp 
      // parent.addView not necessary as this is already done by attachRoot=true
      // view=root due to parent supplied as hierarchy root and attachRoot=true
      view = LayoutInflater.from(this).inflate(R.layout.red, parent, true);
    }
}

The actual results of the parameter variations are documented in the code.

SYNOPSIS: Calling LayoutInflater without specifying root leads to inflate call ignoring the layout parameters from the XML. Calling inflate with root not equal null and attachRoot=true does load the layout parameters, but returns the root object again, which prevents further layout changes to the loaded object (unless you can find it using findViewById()). The calling convention you most likely would like to use is therefore this one:

loadedView = LayoutInflater.from(context)
                .inflate(R.layout.layout_to_load, parent, false);

To help with layout issues, the Layout Inspector is highly recommended.

typecast string to integer - Postgres

Common issue

Naively type casting any string into an integer like so

SELECT ''::integer

Often results to the famous error:

Query failed: ERROR: invalid input syntax for integer: ""

Problem

PostgreSQL has no pre-defined function for safely type casting any string into an integer.

Solution

Create a user-defined function inspired by PHP's intval() function.

CREATE FUNCTION intval(character varying) RETURNS integer AS $$

SELECT
CASE
    WHEN length(btrim(regexp_replace($1, '[^0-9]', '','g')))>0 THEN btrim(regexp_replace($1, '[^0-9]', '','g'))::integer
    ELSE 0
END AS intval;

$$
LANGUAGE SQL
IMMUTABLE
RETURNS NULL ON NULL INPUT;

Usage

/* Example 1 */
SELECT intval('9000');
-- output: 9000

/* Example 2 */
SELECT intval('9gag');
-- output: 9

/* Example 3 */
SELECT intval('the quick brown fox jumps over the lazy dog');
-- output: 0

moving committed (but not pushed) changes to a new branch after pull

One more way assume branch1 - is branch with committed changes branch2 - is desirable branch

git fetch && git checkout branch1
git log

select commit ids that you need to move

git fetch && git checkout branch2
git cherry-pick commit_id_first..commit_id_last
git push

Now revert unpushed commits from initial branch

git fetch && git checkout branch1
git reset --soft HEAD~1

jQuery Call to WebService returns "No Transport" error

I too got this problem and all solutions given above either failed or were not applicable due to client webservice restrictions.

For this, I added an iframe in my page which resided in the client;s server. So when we post our data to the iframe and the iframe then posts it to the webservice. Hence the cross-domain referencing is eliminated.

We added a 2-way origin check to confirm only authorized page posts data to and from the iframe.

Hope it helps

<iframe style="display:none;" id='receiver' name="receiver" src="https://iframe-address-at-client-server">
 </iframe>

//send data to iframe
var hiddenFrame = document.getElementById('receiver').contentWindow;
hiddenFrame.postMessage(JSON.stringify(message), 'https://client-server-url');

//The iframe receives the data using the code:
window.onload = function () {
    var eventMethod = window.addEventListener ? "addEventListener" : "attachEvent";
    var eventer = window[eventMethod];
    var messageEvent = eventMethod == "attachEvent" ? "onmessage" : "message";
    eventer(messageEvent, function (e) {
        var origin = e.origin;
        //if origin not in pre-defined list, break and return
        var messageFromParent = JSON.parse(e.data);
        var json = messageFromParent.data;

        //send json to web service using AJAX   
        //return the response back to source
        e.source.postMessage(JSON.stringify(aJAXResponse), e.origin);
    }, false);
}

Set the default value in dropdownlist using jQuery

$("#dropdownList option[text='it\'s me']").attr("selected","selected"); 

Python: Passing variables between functions

You're just missing one critical step. You have to explicitly pass the return value in to the second function.

def main():
    l = defineAList()
    useTheList(l)

Alternatively:

def main():
    useTheList(defineAList())

Or (though you shouldn't do this! It might seem nice at first, but globals just cause you grief in the long run.):

l = []

def defineAList():
    global l
    l.extend(['1','2','3'])

def main():
    global l
    defineAList()
    useTheList(l)

The function returns a value, but it doesn't create the symbol in any sort of global namespace as your code assumes. You have to actually capture the return value in the calling scope and then use it for subsequent operations.

macro - open all files in a folder

Try the below code:

Sub opendfiles()

Dim myfile As Variant
Dim counter As Integer
Dim path As String

myfolder = "D:\temp\"
ChDir myfolder
myfile = Application.GetOpenFilename(, , , , True)
counter = 1
If IsNumeric(myfile) = True Then
    MsgBox "No files selected"
End If
While counter <= UBound(myfile)
    path = myfile(counter)
    Workbooks.Open path
    counter = counter + 1
Wend

End Sub

In Javascript/jQuery what does (e) mean?

The e argument is short for the event object. For example, you might want to create code for anchors that cancels the default action. To do this you would write something like:

$('a').click(function(e) {
    e.preventDefault();
}

This means when an <a> tag is clicked, prevent the default action of the click event.

While you may see it often, it's not something you have to use within the function even though you have specified it as an argument.

How to get client IP address using jQuery


<html lang="en">
<head>
    <title>Jquery - get ip address</title>
    <script type="text/javascript" src="//cdn.jsdelivr.net/jquery/1/jquery.min.js"></script>
</head>
<body>


<h1>Your Ip Address : <span class="ip"></span></h1>


<script type="text/javascript">
    $.getJSON("http://jsonip.com?callback=?", function (data) {
        $(".ip").text(data.ip);
    });
</script>


</body>
</html>

Is it possible to have a custom facebook like button?

It's possible with a lot of work.

Basically, you have to post likes action via the Open Graph API. Then, you can add a custom design to your like button.

But then, you''ll need to keep track yourself of the likes so a returning user will be able to unlike content he liked previously.

Plus, you'll need to ask user to log into your app and ask them the publish_action permission.

All in all, if you're doing this for an application, it may worth it. For a website where you basically want user to like articles, then this is really to much.

Also, consider that you increase your drop-off rate each time you ask user a permission via a Facebook login.

If you want to see an example, I've recently made an app using the open graph like button, just hover on some photos in the mosaique to see it

How to restart a node.js server

In this case you are restarting your node.js server often because it's in active development and you are making changes all the time. There is a great hot reload script that will handle this for you by watching all your .js files and restarting your node.js server if any of those files have changed. Just the ticket for rapid development and test.

The script and explanation on how to use it are at here at Draco Blue.

Removing object properties with Lodash

You can use _.omit() for emitting the key from a JSON array if you have fewer objects:

_.forEach(data, (d) => {
    _.omit(d, ['keyToEmit1', 'keyToEmit2'])
});

If you have more objects, you can use the reverse of it which is _.pick():

_.forEach(data, (d) => {
    _.pick(d, ['keyToPick1', 'keyToPick2'])
});

Run MySQLDump without Locking Tables

Honestly, I would setup replication for this, as if you don't lock tables you will get inconsistent data out of the dump.

If the dump takes longer time, tables which were already dumped might have changed along with some table which is only about to be dumped.

So either lock the tables or use replication.

Drawing a dot on HTML5 canvas

It seems strange, but nonetheless HTML5 supports drawing lines, circles, rectangles and many other basic shapes, it does not have anything suitable for drawing the basic point. The only way to do so is to simulate a point with whatever you have.

So basically there are 3 possible solutions:

  • draw point as a line
  • draw point as a polygon
  • draw point as a circle

Each of them has their drawbacks.


Line

function point(x, y, canvas){
  canvas.beginPath();
  canvas.moveTo(x, y);
  canvas.lineTo(x+1, y+1);
  canvas.stroke();
}

Keep in mind that we are drawing to South-East direction, and if this is the edge, there can be a problem. But you can also draw in any other direction.


Rectangle

function point(x, y, canvas){
  canvas.strokeRect(x,y,1,1);
}

or in a faster way using fillRect because render engine will just fill one pixel.

function point(x, y, canvas){
  canvas.fillRect(x,y,1,1);
}

Circle

One of the problems with circles is that it is harder for an engine to render them

function point(x, y, canvas){
  canvas.beginPath();
  canvas.arc(x, y, 1, 0, 2 * Math.PI, true);
  canvas.stroke();
}

the same idea as with rectangle you can achieve with fill.

function point(x, y, canvas){
  canvas.beginPath();
  canvas.arc(x, y, 1, 0, 2 * Math.PI, true);
  canvas.fill();
}

Problems with all these solutions:

  • it is hard to keep track of all the points you are going to draw.
  • when you zoom in, it looks ugly

If you are wondering, what is the best way to draw a point, I would go with filled rectangle. You can see my jsperf here with comparison tests

MySQL - length() vs char_length()

varchar(10) will store 10 characters, which may be more than 10 bytes. In indexes, it will allocate the maximium length of the field - so if you are using UTF8-mb4, it will allocate 40 bytes for the 10 character field.

Failed: Error in connection establishment: net::ERR_CONNECTION_REFUSED

Firstly, I would try a non-secure websocket connection. So remove one of the s's from the connection address:

conn = new WebSocket('ws://localhost:8080');

If that doesn't work, then the next thing I would check is your server's firewall settings. You need to open port 8080 both in TCP_IN and TCP_OUT.

jQuery: set selected value of dropdown list?

You need to select jQuery in the dropdown on the left and you have a syntax error because the $(document).ready should end with }); not )}; Check this link.

How to check if a String contains another String in a case insensitive manner in Java?

Yes, contains is case sensitive. You can use java.util.regex.Pattern with the CASE_INSENSITIVE flag for case insensitive matching:

Pattern.compile(Pattern.quote(wantedStr), Pattern.CASE_INSENSITIVE).matcher(source).find();

EDIT: If s2 contains regex special characters (of which there are many) it's important to quote it first. I've corrected my answer since it is the first one people will see, but vote up Matt Quail's since he pointed this out.

HTML Best Practices: Should I use &rsquo; or the special keyboard shortcut?

You should only use &rsquo; if your intention is to make either a closed single quotation mark or an apostrophe. Both of these punctuation marks are curved in shape in most fonts. If your intent is to make a foot mark, go the other route. A foot mark is always a straight vertical mark.

It’s a matter of typography. One way is correct; the other is not.

Installing Android Studio, does not point to a valid JVM installation error

i think you are doing every thing fine just remove ";" from the last of java_home variable. every thing will work fine.

Subversion stuck due to "previous operation has not finished"?

I use tortoise SVN. When clean up failed, check cleanup option

Make sure the option to Break Locks is checked.

Cleanup step

  • left mouse button in explore folder
  • select 'Tortoise SVN' -> 'Clean up...' menu
  • check 'Break Locks' checked and press 'ok'

It already answered ,but sometimes picture helps

enter image description here

What is the command for cut copy paste a file from one directory to other directory

E:>move "blogger code.txt" d:/"blogger code.txt"

    1 file(s) moved.

"blogger code.txt" is a file name

The file move from E: drive to D: drive

How to force the input date format to dd/mm/yyyy?

DEMO : http://jsfiddle.net/shfj70qp/

//dd/mm/yyyy 

var date = new Date();
var month = date.getMonth();
var day = date.getDate();
var year = date.getFullYear();

console.log(month+"/"+day+"/"+year);

The container 'Maven Dependencies' references non existing library - STS

I'm a little late to the party but I'll give my two cents. I just resolved this issue after spending longer than I'd like on it. The above solutions didn't work for me and here's why:

there was a network issue when maven was downloading the required repositories so I actually didn't have the right jars. adding a -U to a maven clean install went and got them for me. So if the above solutions aren't working try this:

  1. Right click on your project -> Choose Run as -> 5 Maven build...
  2. In the Goals field type "clean install -U" and select Run
  3. After that completes right click on your project again and choose Maven -> Update Project and click ok.

Hope it works for you.

How to get the unique ID of an object which overrides hashCode()?

I came up with this solution which works in my case where I have objects created on multiple threads and are serializable:

public abstract class ObjBase implements Serializable
    private static final long serialVersionUID = 1L;
    private static final AtomicLong atomicRefId = new AtomicLong();

    // transient field is not serialized
    private transient long refId;

    // default constructor will be called on base class even during deserialization
    public ObjBase() {
       refId = atomicRefId.incrementAndGet()
    }

    public long getRefId() {
        return refId;
    }
}

NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equalsIgnoreCase(java.lang.String)' on a null object reference

called_from must be null. Add a test against that condition like

if (called_from != null && called_from.equalsIgnoreCase("add")) {

or you could use Yoda conditions (per the Advantages in the linked Wikipedia article it can also solve some types of unsafe null behavior they can be described as placing the constant portion of the expression on the left side of the conditional statement)

if ("add".equalsIgnoreCase(called_from)) { // <-- safe if called_from is null

How do I fix the indentation of selected lines in Visual Studio

Selecting the text to fix, and CtrlK, CtrlF shortcut certainly works. However, I generally find that if a particular method (for instance) has it's indentation messed up, simply removing the closing brace of the method, and re-adding, in fact fixes the indentation anyway, thereby doing without the need to select the code before hand, ergo is quicker. ymmv.

Programmatically go back to previous ViewController in Swift

This one works for me (Swift UI)

struct DetailView: View {
@Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>

  var body: some View {
      VStack {
        Text("This is the detail view")
        Button(action: {
          self.presentationMode.wrappedValue.dismiss()
        }) {
          Text("Back")
        }
      }
    }
}

sklearn error ValueError: Input contains NaN, infinity or a value too large for dtype('float64')

I got the same error message when using sklearn with pandas. My solution is to reset the index of my dataframe df before running any sklearn code:

df = df.reset_index()

I encountered this issue many times when I removed some entries in my df, such as

df = df[df.label=='desired_one']

Flash CS4 refuses to let go

I have found one related behaviour that may help (sounds like your specific problem runs deeper though):

Flash checks whether a source file needs recompiling by looking at timestamps. If its compiled version is older than the source file, it will recompile. But it doesn't check whether the compiled version was generated from the same source file or not.

Specifically, if you have your actionscript files under version control, and you Revert a change, the reverted file will usually have an older timestamp, and Flash will ignore it.

Pull new updates from original GitHub repository into forked GitHub repository

If there is nothing to lose you could also just delete your fork just go to settings... go to danger zone section below and click delete repository. It will ask you to input the repository name and your password after. After that you just fork the original again.

Is jQuery $.browser Deprecated?

Second Question

Will my existing implementations continue to work? If not, is there an easy to implement alternative.

The answer is yes, but not without a little work.

$.browser is an official plugin which was included in older versions of jQuery, so like any plugin you can simple copy it and incorporate it into your project or you can simply add it to the end of any jQuery release.

I have extracted the code for you incase you wish to use it.


// Limit scope pollution from any deprecated API
(function() {

    var matched, browser;

// Use of jQuery.browser is frowned upon.
// More details: http://api.jquery.com/jQuery.browser
// jQuery.uaMatch maintained for back-compat
    jQuery.uaMatch = function( ua ) {
        ua = ua.toLowerCase();

        var match = /(chrome)[ \/]([\w.]+)/.exec( ua ) ||
            /(webkit)[ \/]([\w.]+)/.exec( ua ) ||
            /(opera)(?:.*version|)[ \/]([\w.]+)/.exec( ua ) ||
            /(msie) ([\w.]+)/.exec( ua ) ||
            ua.indexOf("compatible") < 0 && /(mozilla)(?:.*? rv:([\w.]+)|)/.exec( ua ) ||
            [];

        return {
            browser: match[ 1 ] || "",
            version: match[ 2 ] || "0"
        };
    };

    matched = jQuery.uaMatch( navigator.userAgent );
    browser = {};

    if ( matched.browser ) {
        browser[ matched.browser ] = true;
        browser.version = matched.version;
    }

// Chrome is Webkit, but Webkit is also Safari.
    if ( browser.chrome ) {
        browser.webkit = true;
    } else if ( browser.webkit ) {
        browser.safari = true;
    }

    jQuery.browser = browser;

    jQuery.sub = function() {
        function jQuerySub( selector, context ) {
            return new jQuerySub.fn.init( selector, context );
        }
        jQuery.extend( true, jQuerySub, this );
        jQuerySub.superclass = this;
        jQuerySub.fn = jQuerySub.prototype = this();
        jQuerySub.fn.constructor = jQuerySub;
        jQuerySub.sub = this.sub;
        jQuerySub.fn.init = function init( selector, context ) {
            if ( context && context instanceof jQuery && !(context instanceof jQuerySub) ) {
                context = jQuerySub( context );
            }

            return jQuery.fn.init.call( this, selector, context, rootjQuerySub );
        };
        jQuerySub.fn.init.prototype = jQuerySub.fn;
        var rootjQuerySub = jQuerySub(document);
        return jQuerySub;
    };

})();

If you're asking why anyone would need a depreciated plugin, I have prepared the following answer.

First and foremost the answer is compatibility. Since jQuery is plugin based, some developers opted to use $.browser and with the latest releases of jQuery which doesn't include $.browser all those plugins where rendered useless.

jQuery did release a migration plugin, which was created for developers to detect whether their plugin's used any depreciated dependencies such as $.browser.

Although this helped developers patch their plugin's. jQuery dropped $.browser completely so the above fix is probably the only solution until your developers patch or incorporate the above.

About: jQuery.browser

RestClientException: Could not extract response. no suitable HttpMessageConverter found

If the above response by @Ilya Dyoshin didn't still retrieve, try to get the response into a String Object.

(For my self thought the error got solved by the code snippet by Ilya, the response retrieved was a failure(error) from the server.)

HttpHeaders requestHeaders = new HttpHeaders();
requestHeaders.add(HttpHeaders.CONTENT_TYPE, "application/x-www-form-urlencoded");
ResponseEntity<String> st = restTemplate.exchange(url, HttpMethod.POST, httpEntity, String.class); 

And Cast to the ResponseObject DTO (Json)

Gson g = new Gson();
DTO dto = g.fromJson(st.getBody(), DTO.class); 

Writing/outputting HTML strings unescaped

Sometimes it can be tricky to use raw html. Mostly because of XSS vulnerability. If that is a concern, but you still want to use raw html, you can encode the scary parts.

@Html.Raw("(<b>" + Html.Encode("<script>console.log('insert')</script>" + "Hello") + "</b>)")

Results in

(<b>&lt;script&gt;console.log('insert')&lt;/script&gt;Hello</b>)

Pandas convert dataframe to array of tuples

Motivation
Many data sets are large enough that we need to concern ourselves with speed/efficiency. So I offer this solution in that spirit. It happens to also be succinct.

For the sake of comparison, let's drop the index column

df = data_set.drop('index', 1)

Solution
I'll propose the use of zip and map

list(zip(*map(df.get, df)))

[('2012-02-17', 24.75, 25.03),
 ('2012-02-16', 25.0, 25.07),
 ('2012-02-15', 24.99, 25.15),
 ('2012-02-14', 24.68, 25.05),
 ('2012-02-13', 24.62, 24.77),
 ('2012-02-10', 24.38, 24.61)]

It happens to also be flexible if we wanted to deal with a specific subset of columns. We'll assume the columns we've already displayed are the subset we want.

list(zip(*map(df.get, ['data_date', 'data_1', 'data_2'])))

[('2012-02-17', 24.75, 25.03),
 ('2012-02-16', 25.0, 25.07),
 ('2012-02-15', 24.99, 25.15),
 ('2012-02-14', 24.68, 25.05),
 ('2012-02-13', 24.62, 24.77),
 ('2012-02-10', 24.38, 24.61)]

What is Quicker?

Turn's out records is quickest followed by asymptotically converging zipmap and iter_tuples

I'll use a library simple_benchmarks that I got from this post

from simple_benchmark import BenchmarkBuilder
b = BenchmarkBuilder()

import pandas as pd
import numpy as np

def tuple_comp(df): return [tuple(x) for x in df.to_numpy()]
def iter_namedtuples(df): return list(df.itertuples(index=False))
def iter_tuples(df): return list(df.itertuples(index=False, name=None))
def records(df): return df.to_records(index=False).tolist()
def zipmap(df): return list(zip(*map(df.get, df)))

funcs = [tuple_comp, iter_namedtuples, iter_tuples, records, zipmap]
for func in funcs:
    b.add_function()(func)

def creator(n):
    return pd.DataFrame({"A": random.randint(n, size=n), "B": random.randint(n, size=n)})

@b.add_arguments('Rows in DataFrame')
def argument_provider():
    for n in (10 ** (np.arange(4, 11) / 2)).astype(int):
        yield n, creator(n)

r = b.run()

Check the results

r.to_pandas_dataframe().pipe(lambda d: d.div(d.min(1), 0))

        tuple_comp  iter_namedtuples  iter_tuples   records    zipmap
100       2.905662          6.626308     3.450741  1.469471  1.000000
316       4.612692          4.814433     2.375874  1.096352  1.000000
1000      6.513121          4.106426     1.958293  1.000000  1.316303
3162      8.446138          4.082161     1.808339  1.000000  1.533605
10000     8.424483          3.621461     1.651831  1.000000  1.558592
31622     7.813803          3.386592     1.586483  1.000000  1.515478
100000    7.050572          3.162426     1.499977  1.000000  1.480131

r.plot()

enter image description here

Google Maps v3 - limit viewable area and zoom level

As of middle 2016, there is no official way to restrict viewable area. Most of ad-hoc solutions to restrict the bounds have a flaw though, because they don't restrict the bounds exactly to fit the map view, they only restrict it if the center of the map is out of the specified bounds. If you want to restrict the bounds to overlaying image like me, this can result in a behavior like illustrated below, where the underlaying map is visible under our image overlay:

enter image description here

To tackle this issue, I have created a library, which successfully restrict the bounds so you cannot pan out of the overlay.

However, as other existing solutions, it has a "vibrating" issue. When the user pans the map aggressively enough, after they release the left mouse button, the map still continues panning by itself, gradually slowing. I always return the map back to the bounds, but that results in kind of vibrating. This panning effect cannot be stopped with any means provided by the Js API at the moment. It seems that until google adds support for something like map.stopPanningAnimation() we won't be able to create a smooth experience.

Example using the mentioned library, the smoothest strict bounds experience I was able to get:

_x000D_
_x000D_
function initialise(){_x000D_
  _x000D_
  var myOptions = {_x000D_
     zoom: 5,_x000D_
     center: new google.maps.LatLng(0,0),_x000D_
     mapTypeId: google.maps.MapTypeId.ROADMAP,_x000D_
  };_x000D_
  var map = new google.maps.Map(document.getElementById('map'), myOptions);_x000D_
  _x000D_
  addStrictBoundsImage(map);_x000D_
}_x000D_
_x000D_
function addStrictBoundsImage(map){_x000D_
 var bounds = new google.maps.LatLngBounds(_x000D_
  new google.maps.LatLng(62.281819, -150.287132),_x000D_
  new google.maps.LatLng(62.400471, -150.005608));_x000D_
_x000D_
 var image_src = 'https://developers.google.com/maps/documentation/' +_x000D_
  'javascript/examples/full/images/talkeetna.png';_x000D_
_x000D_
 var strict_bounds_image = new StrictBoundsImage(bounds, image_src, map);_x000D_
}
_x000D_
<script type="text/javascript" src="http://www.google.com/jsapi"></script>_x000D_
      <script type="text/javascript">_x000D_
        google.load("maps", "3",{other_params:"sensor=false"});_x000D_
      </script>_x000D_
<body style="margin:0px; padding:0px;" onload="initialise()">_x000D_
  <div id="map" style="height:400px; width:500px;"></div>_x000D_
     <script  type="text/javascript"src="https://raw.githubusercontent.com/matej-pavla/StrictBoundsImage/master/StrictBoundsImage.js"></script>_x000D_
</body>
_x000D_
_x000D_
_x000D_

The library is also able to calculate the minimum zoom restriction automatically. It then restricts the zoom level using minZoom map's attribute.

Hopefully this helps someone who wants a solution which fully respect the given boundaries and doesn't want to allow panning out of them.

How to color the Git console?

For example see https://web.archive.org/web/20080506194329/http://www.arthurkoziel.com/2008/05/02/git-configuration/

The interesting part is

Colorized output:

git config --global color.branch auto
git config --global color.diff auto
git config --global color.interactive auto
git config --global color.status auto

What does the "yield" keyword do?

yield is like a return element for a function. The difference is, that the yield element turns a function into a generator. A generator behaves just like a function until something is 'yielded'. The generator stops until it is next called, and continues from exactly the same point as it started. You can get a sequence of all the 'yielded' values in one, by calling list(generator()).

jQuery: serialize() form and other parameters

serialize() effectively turns the form values into a valid querystring, as such you can simply append to the string:

$.ajax({
    type : 'POST',
    url : 'url',
    data : $('#form').serialize() + "&par1=1&par2=2&par3=232"
}

How to select the first element of a set with JSTL?

If you only want the first element of a set (and you are certain there is at least one element) you can do the following:

<c:choose>
    <c:when test="${dealership.administeredBy.size() == 1}">
        Hello ${dealership.administeredBy.iterator().next().firstName},<br/>
    </c:when>
    <c:when test="${dealership.administeredBy.size() > 1}">
        Hello Administrators,<br/>
    </c:when>
    <c:otherwise>
    </c:otherwise>
</c:choose>

Can't Find Theme.AppCompat.Light for New Android ActionBar Support

You need to do next:

  1. File->Import (android-sdk\extras\android\support\v7). Choose "AppCompat"
  2. Project-> properties->Android. In the section library "Add" and choose "AppCompat"
  3. That is all!

Note: if you are using "android:showAsAction" in menu item, you need to change prefix android as in the example http://developer.android.com/guide/topics/ui/actionbar.html

Is java.sql.Timestamp timezone specific?

I think the correct answer should be java.sql.Timestamp is NOT timezone specific. Timestamp is a composite of java.util.Date and a separate nanoseconds value. There is no timezone information in this class. Thus just as Date this class simply holds the number of milliseconds since January 1, 1970, 00:00:00 GMT + nanos.

In PreparedStatement.setTimestamp(int parameterIndex, Timestamp x, Calendar cal) Calendar is used by the driver to change the default timezone. But Timestamp still holds milliseconds in GMT.

API is unclear about how exactly JDBC driver is supposed to use Calendar. Providers seem to feel free about how to interpret it, e.g. last time I worked with MySQL 5.5 Calendar the driver simply ignored Calendar in both PreparedStatement.setTimestamp and ResultSet.getTimestamp.

Docker: How to delete all local Docker images

Here is short and quick solution I used

Docker provides a single command that will clean up any resources — images, containers, volumes, and networks — that are dangling (not associated with a container):

docker system prune

To additionally remove any stopped containers and all unused images (not just dangling images), add the -a flag to the command:

docker system prune -a


For more details visit link

Detect when a window is resized using JavaScript ?

This can be achieved with the onresize property of the GlobalEventHandlers interface in JavaScript, by assigning a function to the onresize property, like so:

window.onresize = functionRef;

The following code snippet demonstrates this, by console logging the innerWidth and innerHeight of the window whenever it's resized. (The resize event fires after the window has been resized)

_x000D_
_x000D_
function resize() {_x000D_
  console.log("height: ", window.innerHeight, "px");_x000D_
  console.log("width: ", window.innerWidth, "px");_x000D_
}_x000D_
_x000D_
window.onresize = resize;
_x000D_
<p>In order for this code snippet to work as intended, you will need to either shrink your browser window down to the size of this code snippet, or fullscreen this code snippet and resize from there.</p>
_x000D_
_x000D_
_x000D_

How to change an application icon programmatically in Android?

As mentioned before you need use <activity-alias> to change the application icon. To avoid killing the application after enabling appropriate activity-alias you need to do this after the application is killed. To find out if the application was killed you can use this method

  1. Create activity aliases in AndroidManifest.xml
<activity android:name=".ui.MainActivity"/>

<activity-alias
    android:name=".one"
    android:icon="@mipmap/ic_launcher_one"
    android:targetActivity=".ui.MainActivity"
    android:enabled="true">

    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>

</activity-alias>

<activity-alias
    android:name=".two"
    android:icon="@mipmap/ic_launcher_two"
    android:targetActivity=".ui.MainActivity"
    android:enabled="false">

    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>

</activity-alias>
  1. ?reate a service that will change the active activity-alias after killing the application. You need store the name of new active activity-alias somewhere (e.g. SharedPreferences)
class ChangeAppIconService: Service() {
    private val aliases = arrayOf(".one", ".two")

    override fun onBind(intent: Intent?): IBinder? = null

    override fun onTaskRemoved(rootIntent: Intent?) {
        changeAppIcon()
        stopSelf()
    }

    fun changeAppIcon() {
        val sp = getSharedPreferences("appSettings", Context.MODE_PRIVATE)

        sp.getString("activeActivityAlias", ".one").let { aliasName ->
            if (!isAliasEnabled(aliasName)) {
                setAliasEnabled(aliasName)
            }
        }
    }

    private fun isAliasEnabled(aliasName: String): Boolean {
        return packageManager.getComponentEnabledSetting(
            ComponentName(
                this,
                "${BuildConfig.APPLICATION_ID}$aliasName"
            )
        ) == PackageManager.COMPONENT_ENABLED_STATE_ENABLED
    }

    private fun setAliasEnabled(aliasName: String) {
        aliases.forEach {
            val action = if (it == aliasName)
                PackageManager.COMPONENT_ENABLED_STATE_ENABLED
            else
                PackageManager.COMPONENT_ENABLED_STATE_DISABLED
                
            packageManager.setComponentEnabledSetting(
                ComponentName(
                    this,
                    "${BuildConfig.APPLICATION_ID}$aliasName"
                ),
                action,
                PackageManager.DONT_KILL_APP
            )
        }
    }
}
  1. Add service to AndroidManifest.xml
<service 
    android:name=".ChangeAppIconService"
    android:stopWithTask="false"
    />
  1. Start ChangeAppIconService in MainActivity.onCreate
class MainActivity: Activity {

    ...

    override fun onCreate(savedInstanceState: Bundle?) {
       ...

       startService(Intent(this, ChangeAppIconService::class.java))

       ...
    }

    ...

}

Two's Complement in Python

Here's a version to convert each value in a hex string to it's two's complement version.


In [5159]: twoscomplement('f0079debdd9abe0fdb8adca9dbc89a807b707f')                                                                                                 
Out[5159]: '10097325337652013586346735487680959091'


def twoscomplement(hm): 
   twoscomplement='' 
   for x in range(0,len(hm)): 
       value = int(hm[x],16) 
       if value % 2 == 1: 
         twoscomplement+=hex(value ^ 14)[2:] 
       else: 
         twoscomplement+=hex(((value-1)^15)&0xf)[2:] 
   return twoscomplement            

Cloning specific branch

you can use this command for particular branch clone :

git clone <url of repo> -b <branch name to be cloned>

Eg: git clone https://www.github.com/Repo/FirstRepo -b master

How to get length of a string using strlen function

For C++ strings, there's no reason to use strlen. Just use string::length:

std::cout << str.length() << std::endl;

You should strongly prefer this to strlen(str.c_str()) for the following reasons:

  1. Clarity: The length() (or size()) member functions unambiguously give back the length of the string. While it's possible to figure out what strlen(str.c_str()) does, it forces the reader to pause for a bit.

  2. Efficiency: length() and size() run in time O(1), while strlen(str.c_str()) will take Θ(n) time to find the end of the string.

  3. Style: It's good to prefer the C++ versions of functions to the C versions unless there's a specific reason to do so otherwise. This is why, for example, it's usually considered better to use std::sort over qsort or std::lower_bound over bsearch, unless some other factors come into play that would affect performance.

The only reason I could think of where strlen would be useful is if you had a C++-style string that had embedded null characters and you wanted to determine how many characters appeared before the first of them. (That's one way in which strlen differs from string::length; the former stops at a null terminator, and the latter counts all the characters in the string). But if that's the case, just use string::find:

size_t index = str.find(0);
if (index == str::npos) index = str.length();
std::cout << index << std::endl;

Hope this helps!

Get human readable version of file size?

The following works in Python 3.6+, is, in my opinion, the easiest to understand answer on here, and lets you customize the amount of decimal places used.

def human_readable_size(size, decimal_places=2):
    for unit in ['B', 'KiB', 'MiB', 'GiB', 'TiB', 'PiB']:
        if size < 1024.0 or unit == 'PiB':
            break
        size /= 1024.0
    return f"{size:.{decimal_places}f} {unit}"

Detect IE version (prior to v9) in JavaScript

The most comprehensive JS script I found to check for versions of IE is http://www.pinlady.net/PluginDetect/IE/. The entire library is at http://www.pinlady.net/PluginDetect/Browsers/.

With IE10, conditional statements are no longer supported.

With IE11, the user agent no longer contains MSIE. Also, using the user agent is not reliable because that can be modified.

Using the PluginDetect JS script, you can detect for IE and detect the exact versions by using very specific and well-crafted code that targets specific IE versions. This is very useful when you care exactly what version of browser you are working with.

Image resizing client-side with JavaScript before upload to the server

Yes, with modern browsers this is totally doable. Even doable to the point of uploading the file specifically as a binary file having done any number of canvas alterations.

http://jsfiddle.net/bo40drmv/

(this answer is a improvement of the accepted answer here)

Keeping in mind to catch process the result submission in the PHP with something akin to:

//File destination
$destination = "/folder/cropped_image.png";
//Get uploaded image file it's temporary name
$image_tmp_name = $_FILES["cropped_image"]["tmp_name"][0];
//Move temporary file to final destination
move_uploaded_file($image_tmp_name, $destination);

If one worries about Vitaly's point, you can try some of the cropping and resizing on the working jfiddle.

Cannot resolve symbol HttpGet,HttpClient,HttpResponce in Android Studio

HttpClient was deprecated in API Level 22 and removed in API Level 23. You have to use URLConnection.

Error: allowDefinition='MachineToApplication' beyond application level

If you have MVC project with enabled views build, one of the solution is to delete obj folder before build. Add to project file:

<Target Name="BeforeBuild">
    <!-- Remove obj folder -->
    <RemoveDir Directories="$(BaseIntermediateOutputPath)" />
    <!-- Remove bin folder -->
    <RemoveDir Directories="$(BaseOutputPath)" />
</Target>

Here is article: How to remove bin and/or obj folder before the build or deploy

How to change font in ipython notebook

The new location of the theme file is: ~/.jupyter/custom/custom.css

jQuery object equality

First order your object based on key using this function

function sortObject(o) {
    return Object.keys(o).sort().reduce((r, k) => (r[k] = o[k], r), {});
}

Then, compare the stringified version of your object, using this funtion

function isEqualObject(a,b){
    return JSON.stringify(sortObject(a)) == JSON.stringify(sortObject(b));
}

Here is an example

Assuming objects keys are ordered differently and are of the same values

var obj1 = {"hello":"hi","world":"earth"}
var obj2 = {"world":"earth","hello":"hi"}

isEqualObject(obj1,obj2);//returns true

Creating a recursive method for Palindrome

public static boolean isPalindrome(String p)
    {
        if(p.length() == 0 || p.length() == 1)
            // if length =0 OR 1 then it is
            return true; 

         if(p.substring(0,1).equalsIgnoreCase(p.substring(p.length()-1))) 
            return isPalindrome(p.substring(1, p.length()-1));


        return false;
    }

This solution is not case sensitive. Hence, for example, if you have the following word : "adinida", then you will get true if you do "Adninida" or "adninida" or "adinidA", which is what we want.

I like @JigarJoshi answer, but the only problem with his approach is that it will give you false for words which contains caps.

Remove background drawable programmatically in Android

This work for me:

yourview.setBackground(null);

Copy filtered data to another sheet using VBA

When i need to copy data from filtered table i use range.SpecialCells(xlCellTypeVisible).copy. Where the range is range of all data (without a filter).

Example:

Sub copy()
     'source worksheet
     dim ws as Worksheet
     set ws = Application.Worksheets("Data")' set you source worksheet here
     dim data_end_row_number as Integer
     data_end_row_number = ws.Range("B3").End(XlDown).Row.Number
    'enable filter
    ws.Range("B2:F2").AutoFilter Field:=2, Criteria1:="hockey", VisibleDropDown:=True
    ws.Range("B3:F" & data_end_row_number).SpecialCells(xlCellTypeVisible).Copy
    Application.Worksheets("Hoky").Range("B3").Paste
    'You have to add headers to Hoky worksheet
end sub

Clearing input in vuejs form

I had a situation where i was working with a custom component and i needed to clear the form data.

But only if the page was in 'create' form state, and if the page was not being used to edit an existing item. So I made a method.

I called this method inside a watcher on custom component file, and not the vue page that uses the custom component. If that makes sense.

The entire form $ref was only available to me on the Base Custom Component.

<!-- Custom component HTML -->
<template>
  <v-form ref="form" v-model="valid" @submit.prevent>
    <slot v-bind="{ formItem, formState, valid }"></slot>
  </v-form>
</template>

watch: {
  value() {
    // Some other code here
    this.clearFormDataIfNotEdit(this)
    // Some other code here too
  }
}
... some other stuff ....

methods: {
  clearFormDataIfNotEdit(objct) {
    if (objct.formstate === 'create' && objct.formItem.id === undefined) {
       objct.$refs.form.reset()
    }
  },
}

Basically i checked to see if the form data had an ID, if it did not, and the state was on create, then call the obj.$ref.form.reset() if i did this directly in the watcher, then it would be this.$ref.form.reset() obvs.

But you can only call the $ref from the page which it's referenced. Which is what i wanted to call out with this answer.

How to set the timezone in Django?

Valid timeZone values are based on the tz (timezone) database used by Linux and other Unix systems. The values are strings (xsd:string) in the form “Area/Location,” in which:

Area is a continent or ocean name. Area currently includes:

  • Africa
  • America (both North America and South America)
  • Antarctica
  • Arctic
  • Asia
  • Atlantic
  • Australia
  • Europe
  • Etc (administrative zone. For example, “Etc/UTC” represents Coordinated Universal Time.)
  • Indian
  • Pacific

Location is the city, island, or other regional name.

The zone names and output abbreviations adhere to POSIX (portable operating system interface) UNIX conventions, which uses positive (+) signs west of Greenwich and negative (-) signs east of Greenwich, which is the opposite of what is generally expected. For example, “Etc/GMT+4” corresponds to 4 hours behind UTC (that is, west of Greenwich) rather than 4 hours ahead of UTC (Coordinated Universal Time) (east of Greenwich).

Here is a list all valid timezones

You can change time zone in your settings.py as follows

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'Asia/Kolkata'

USE_I18N = True

USE_L10N = True

USE_TZ = True

How to match "any character" in regular expression?

Yes that will work, though note that . will not match newlines unless you pass the DOTALL flag when compiling the expression:

Pattern pattern = Pattern.compile(".*123", Pattern.DOTALL);
Matcher matcher = pattern.matcher(inputStr);
boolean matchFound = matcher.matches();

Append text to file from command line without using io redirection

If you don't mind using sed then,

$ cat test 
this is line 1
$ sed -i '$ a\this is line 2 without redirection' test 
$ cat test 
this is line 1
this is line 2 without redirection

As the documentation may be a bit long to go through, some explanations :

  • -i means an inplace transformation, so all changes will occur in the file you specify
  • $ is used to specify the last line
  • a means append a line after
  • \ is simply used as a delimiter

What is __pycache__?

__pycache__ is a folder containing Python 3 bytecode compiled and ready to be executed.

I don't recommend routinely deleting these files or suppressing creation during development as it may hurt performance. Just have a recursive command ready (see below) to clean up when needed as bytecode can become stale in edge cases (see comments).

Python programmers usually ignore bytecode. Indeed __pycache__ and *.pyc are common lines to see in .gitignore files. Bytecode is not meant for distribution and can be disassembled using dis module.


If you are using OS X you can easily hide all of these folders in your project by running following command from the root folder of your project.

find . -name '__pycache__' -exec chflags hidden {} \;

Replace __pycache__ with *.pyc for Python 2.

This sets a flag on all those directories (.pyc files) telling Finder/Textmate 2 to exclude them from listings. Importantly the bytecode is there, it's just hidden.

Rerun the command if you create new modules and wish to hide new bytecode or if you delete the hidden bytecode files.


On Windows the equivalent command might be (not tested, batch script welcome):

dir * /s/b | findstr __pycache__ | attrib +h +s +r

Which is same as going through the project hiding folders using right-click > hide...


Running unit tests is one scenario (more in comments) where deleting the *.pyc files and __pycache__ folders is indeed useful. I use the following lines in my ~/.bash_profile and just run cl to clean up when needed.

alias cpy='find . -name "__pycache__" -delete'
alias cpc='find . -name "*.pyc"       -delete'
...
alias cl='cpy && cpc && ...'

and more lately

# pip install pyclean
pyclean .

WAITING at sun.misc.Unsafe.park(Native Method)

From the stack trace it's clear that, the ThreadPoolExecutor > Worker thread started and it's waiting for the task to be available on the BlockingQueue(DelayedWorkQueue) to pick the task and execute.So this thread will be in WAIT status only as long as get a SIGNAL from the publisher thread.

Oracle REPLACE() function isn't handling carriage-returns & line-feeds

If your newline character is CRLF, that means it's a CHR(13) followed by CHR(10). If you REPLACE(input, CHR(10), '_'), that turns into CHR(13) followed by an underscore. Since CR on its own can be just as well rendered as a newline character, it'll appear to you as if an underscore has ben inserted after your newline, but actually only half of your newline has been replaced.

Use REPLACE(REPLACE(input, CHR(13)), CHR(10)) to replace all CR's and LF's.

Spin or rotate an image on hover

You can use CSS3 transitions with rotate() to spin the image on hover.

Rotating image :

_x000D_
_x000D_
img {_x000D_
  border-radius: 50%;_x000D_
  -webkit-transition: -webkit-transform .8s ease-in-out;_x000D_
          transition:         transform .8s ease-in-out;_x000D_
}_x000D_
img:hover {_x000D_
  -webkit-transform: rotate(360deg);_x000D_
          transform: rotate(360deg);_x000D_
}
_x000D_
<img src="https://i.stack.imgur.com/BLkKe.jpg" width="100" height="100"/>
_x000D_
_x000D_
_x000D_

Here is a fiddle DEMO


More info and references :

  • a guide about CSS transitions on MDN
  • a guide about CSS transforms on MDN
  • browser support table for 2d transforms on caniuse.com
  • browser support table for transitions on caniuse.com

How to execute a JavaScript function when I have its name as a string

With ES6 you could to access class methods by name:

class X {
  method1(){
    console.log("1");
  }
  method2(){
    this['method1']();
    console.log("2");
  }
}
let x  = new X();
x['method2']();

the output would be:

1
2

Ubuntu, how do you remove all Python 3 but not 2

neither try any above ways nor sudo apt autoremove python3 because it will remove all gnome based applications from your system including gnome-terminal. In case if you have done that mistake and left with kernal only than trysudo apt install gnome on kernal.

try to change your default python version instead removing it. you can do this through bashrc file or export path command.

Altering a column: null to not null

As long as the column is not a unique identifier

UPDATE table set columnName = 0 where columnName is null

Then

Alter the table and set the field to non null and specify a default value of 0

C#: Waiting for all threads to complete

Possible solution:

var tasks = dataList
    .Select(data => Task.Factory.StartNew(arg => DoThreadStuff(data), TaskContinuationOptions.LongRunning | TaskContinuationOptions.PreferFairness))
    .ToArray();

var timeout = TimeSpan.FromMinutes(1);
Task.WaitAll(tasks, timeout);

Assuming dataList is the list of items and each item needs to be processed in a separate thread.

Play infinitely looping video on-load in HTML5

As of April 2018, Chrome (along with several other major browsers) now require the muted attribute too.

Therefore, you should use

<video width="320" height="240" autoplay loop muted>
  <source src="movie.mp4" type="video/mp4" />
</video>

Remove all whitespaces from NSString

That is for removing any space that is when you getting text from any text field but if you want to remove space between string you can use

xyz =[xyz.text stringByReplacingOccurrencesOfString:@" " withString:@""];

It will replace empty space with no space and empty field is taken care of by below method:

searchbar.text=[searchbar.text stringByTrimmingCharactersInSet: [NSCharacterSet whitespaceCharacterSet]];

How to iterate through XML in Powershell?

PowerShell has built-in XML and XPath functions. You can use the Select-Xml cmdlet with an XPath query to select nodes from XML object and then .Node.'#text' to access node value.

[xml]$xml = Get-Content $serviceStatePath
$nodes = Select-Xml "//Object[Property/@Name='ServiceState' and Property='Running']/Property[@Name='DisplayName']" $xml
$nodes | ForEach-Object {$_.Node.'#text'}

Or shorter

[xml]$xml = Get-Content $serviceStatePath
Select-Xml "//Object[Property/@Name='ServiceState' and Property='Running']/Property[@Name='DisplayName']" $xml |
  % {$_.Node.'#text'}

In Javascript, how do I check if an array has duplicate values?

If you have an ES2015 environment (as of this writing: io.js, IE11, Chrome, Firefox, WebKit nightly), then the following will work, and will be fast (viz. O(n)):

function hasDuplicates(array) {
    return (new Set(array)).size !== array.length;
}

If you only need string values in the array, the following will work:

function hasDuplicates(array) {
    var valuesSoFar = Object.create(null);
    for (var i = 0; i < array.length; ++i) {
        var value = array[i];
        if (value in valuesSoFar) {
            return true;
        }
        valuesSoFar[value] = true;
    }
    return false;
}

We use a "hash table" valuesSoFar whose keys are the values we've seen in the array so far. We do a lookup using in to see if that value has been spotted already; if so, we bail out of the loop and return true.


If you need a function that works for more than just string values, the following will work, but isn't as performant; it's O(n2) instead of O(n).

function hasDuplicates(array) {
    var valuesSoFar = [];
    for (var i = 0; i < array.length; ++i) {
        var value = array[i];
        if (valuesSoFar.indexOf(value) !== -1) {
            return true;
        }
        valuesSoFar.push(value);
    }
    return false;
}

The difference is simply that we use an array instead of a hash table for valuesSoFar, since JavaScript "hash tables" (i.e. objects) only have string keys. This means we lose the O(1) lookup time of in, instead getting an O(n) lookup time of indexOf.

How to generate a random string in Ruby

I use this for generating random URL friendly strings with a guaranteed maximum length:

string_length = 8
rand(36**string_length).to_s(36)

It generates random strings of lowercase a-z and 0-9. It's not very customizable but it's short and clean.

How to grep a text file which contains some binary data?

you can do

strings test.log | grep -i

this will convert give output as a readable string to grep.

Squash my last X commits together using Git

First I find out the number of commits between my feature branch and current master branch by

git checkout master
git rev-list master.. --count

Then, I create another branch based out my-feature branch, keep my-feature branch untouched.

Lastly, I run

git checkout my-feature
git checkout -b my-rebased-feature
git checkout master
git checkout my-rebased-feature
git rebase master
git rebase head^x -i
// fixup/pick/rewrite
git push origin my-rebased-feature -f // force, if my-rebased-feature was ever pushed, otherwise no need for -f flag
// make a PR with clean history, delete both my-feature and my-rebased-feature after merge

Hope it helps, thanks.

How do I enable/disable log levels in Android?

A common way is to make an int named loglevel, and define its debug level based on loglevel.

public static int LOGLEVEL = 2;
public static boolean ERROR = LOGLEVEL > 0;
public static boolean WARN = LOGLEVEL > 1;
...
public static boolean VERBOSE = LOGLEVEL > 4;

    if (VERBOSE) Log.v(TAG, "Message here"); // Won't be shown
    if (WARN) Log.w(TAG, "WARNING HERE");    // Still goes through

Later, you can just change the LOGLEVEL for all debug output level.

Merge two json/javascript arrays in to one array

Since you are using jQuery. How about the jQuery.extend() method?

http://api.jquery.com/jQuery.extend/

Description: Merge the contents of two or more objects together into the first object.

Shortcuts in Objective-C to concatenate NSStrings

Use stringByAppendingString: this way:

NSString *string1, *string2, *result;

string1 = @"This is ";
string2 = @"my string.";

result = [result stringByAppendingString:string1];
result = [result stringByAppendingString:string2];

OR

result = [result stringByAppendingString:@"This is "];
result = [result stringByAppendingString:@"my string."];

Return value in SQL Server stored procedure

I can recommend make pre-init of future index value, this is very usefull in a lot of case like multi work, some export e.t.c.

just create additional User_Seq table: with two fields: id Uniq index and SeqVal nvarchar(1)

and create next SP, and generated ID value from this SP and put to new User row!

CREATE procedure [dbo].[User_NextValue]
as
begin
    set NOCOUNT ON


    declare @existingId int = (select isnull(max(UserId)+1, 0)  from dbo.User)

    insert into User_Seq (SeqVal) values ('a')
    declare @NewSeqValue int = scope_identity()     

    if @existingId > @NewSeqValue 
    begin  

        set identity_insert User_Seq  on
        insert into User_Seq (SeqID) values (@existingId)     
        set @NewSeqValue = scope_identity()     
    end

    delete from User_Seq WITH (READPAST)

return @NewSeqValue

end

How to get screen dimensions as pixels in Android

Find width and height of the screen:

width = getWindowManager().getDefaultDisplay().getWidth();
height = getWindowManager().getDefaultDisplay().getHeight();

Using this, we can get the latest and above SDK 13.

// New width and height
int version = android.os.Build.VERSION.SDK_INT;
Log.i("", " name == "+ version);
Display display = getWindowManager().getDefaultDisplay();
int width;
if (version >= 13) {
    Point size = new Point();
    display.getSize(size);
    width = size.x;
    Log.i("width", "if =>" +width);
}
else {
    width = display.getWidth();
    Log.i("width", "else =>" +width);
}

remote rejected master -> master (pre-receive hook declined)

I got the same error when I ran git status :

$ git status
On branch master
Your branch is ahead of 'origin/master' by 1 commit.
  (use "git push" to publish your local commits)
nothing to commit, working directory clean

To fix it I can run:

$ git push and run 
$ git push heroku master

Insert data using Entity Framework model

[HttpPost] // it use when you write logic on button click event

public ActionResult DemoInsert(EmployeeModel emp)
{
    Employee emptbl = new Employee();    // make object of table
    emptbl.EmpName = emp.EmpName;
    emptbl.EmpAddress = emp.EmpAddress;  // add if any field you want insert
    dbc.Employees.Add(emptbl);           // pass the table object 
    dbc.SaveChanges();

    return View();
}

How to call a Parent Class's method from Child Class in Python?

There's a super() in Python too. It's a bit wonky, because of Python's old- and new-style classes, but is quite commonly used e.g. in constructors:

class Foo(Bar):
    def __init__(self):
        super(Foo, self).__init__()
        self.baz = 5

DataTables: Cannot read property 'length' of undefined

In my case, i had to assign my json to an attribute called aaData just like in Datatables ajax example which data looked like this.

Passing an array/list into a Python function

You don't need to use the asterisk to accept a list.

Simply give the argument a name in the definition, and pass in a list like

def takes_list(a_list):
    for item in a_list:
         print item

Proxy setting for R

Simplest way to get everything working in RStudio under Windows 10:

Open up Internet Explorer, select Internet Options:

enter image description here


Open editor for Environment variables:

enter image description here


Add a variable HTTP_PROXY in form:

HTTP_PROXY=http://username:password@localhost:port/

Example:

HTTP_PROXY=http://John:JohnPassword@localhost:8080/    

enter image description here


RStudio should work:

enter image description here

Is right click a Javascript event?

This is worked with me

if (evt.xa.which == 3) 
{
    alert("Right mouse clicked");
}

Encrypt and Decrypt in Java

You may want to use the jasypt library (Java Simplified Encryption), which is quite easy to use. ( Also, it's recommended to check against the encrypted password rather than decrypting the encrypted password )

To use jasypt, if you're using maven, you can include jasypt into your pom.xml file as follows:

<dependency>
    <groupId>org.jasypt</groupId>
    <artifactId>jasypt</artifactId>
    <version>1.9.3</version>
    <scope>compile</scope>
</dependency>

And then to encrypt the password, you can use StrongPasswordEncryptor

public static String encryptPassword(String inputPassword) {
    StrongPasswordEncryptor encryptor = new StrongPasswordEncryptor();
    return encryptor.encryptPassword(inputPassword);
}

Note: the encrypted password is different every time you call encryptPassword but the checkPassword method can still check that the unencrypted password still matches each of the encrypted passwords.

And to check the unencrypted password against the encrypted password, you can use the checkPassword method:

public static boolean checkPassword(String inputPassword, String encryptedStoredPassword) {
    StrongPasswordEncryptor encryptor = new StrongPasswordEncryptor();
    return encryptor.checkPassword(inputPassword, encryptedStoredPassword);
}

The page below provides detailed information on the complexities involved in creating safe encrypted passwords.

http://www.jasypt.org/howtoencryptuserpasswords.html

Cannot install NodeJs: /usr/bin/env: node: No such file or directory

For my case link did NOT work as follow

ln -s /usr/bin/nodejs /usr/bin/node

But you can open /usr/local/bin/lessc as root, and change the first line from node to nodejs.

-#!/usr/bin/env node

+#!/usr/bin/env nodejs

How do I sort a list of dictionaries by a value of the dictionary?

import operator

To sort the list of dictionaries by key='name':

list_of_dicts.sort(key=operator.itemgetter('name'))

To sort the list of dictionaries by key='age':

list_of_dicts.sort(key=operator.itemgetter('age'))

Git commit in terminal opens VIM, but can't get back to terminal

not really the answer to the VIM problem but you could use the command line to also enter the commit message:

git commit -m "This is the first commit"

How to check if ZooKeeper is running or up from command prompt?

I did some test:

When it's running:

$ /usr/lib/zookeeper/bin/zkServer.sh status
JMX enabled by default
Using config: /usr/lib/zookeeper/bin/../conf/zoo.cfg
Mode: follower

When it's stopped:

$ zkServer status                                                                                                                                
JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo.cfg
Error contacting service. It is probably not running.

I'm not running on the same machine, but you get the idea.

Check if element is visible on screen

--- Shameless plug ---
I have added this function to a library I created vanillajs-browser-helpers: https://github.com/Tokimon/vanillajs-browser-helpers/blob/master/inView.js
-------------------------------

Well BenM stated, you need to detect the height of the viewport + the scroll position to match up with your top position. The function you are using is ok and does the job, though its a bit more complex than it needs to be.

If you don't use jQuery then the script would be something like this:

function posY(elm) {
    var test = elm, top = 0;

    while(!!test && test.tagName.toLowerCase() !== "body") {
        top += test.offsetTop;
        test = test.offsetParent;
    }

    return top;
}

function viewPortHeight() {
    var de = document.documentElement;

    if(!!window.innerWidth)
    { return window.innerHeight; }
    else if( de && !isNaN(de.clientHeight) )
    { return de.clientHeight; }
    
    return 0;
}

function scrollY() {
    if( window.pageYOffset ) { return window.pageYOffset; }
    return Math.max(document.documentElement.scrollTop, document.body.scrollTop);
}

function checkvisible( elm ) {
    var vpH = viewPortHeight(), // Viewport Height
        st = scrollY(), // Scroll Top
        y = posY(elm);
    
    return (y > (vpH + st));
}

Using jQuery is a lot easier:

function checkVisible( elm, evalType ) {
    evalType = evalType || "visible";

    var vpH = $(window).height(), // Viewport Height
        st = $(window).scrollTop(), // Scroll Top
        y = $(elm).offset().top,
        elementHeight = $(elm).height();

    if (evalType === "visible") return ((y < (vpH + st)) && (y > (st - elementHeight)));
    if (evalType === "above") return ((y < (vpH + st)));
}

This even offers a second parameter. With "visible" (or no second parameter) it strictly checks whether an element is on screen. If it is set to "above" it will return true when the element in question is on or above the screen.

See in action: http://jsfiddle.net/RJX5N/2/

I hope this answers your question.

-- IMPROVED VERSION--

This is a lot shorter and should do it as well:

function checkVisible(elm) {
  var rect = elm.getBoundingClientRect();
  var viewHeight = Math.max(document.documentElement.clientHeight, window.innerHeight);
  return !(rect.bottom < 0 || rect.top - viewHeight >= 0);
}

with a fiddle to prove it: http://jsfiddle.net/t2L274ty/1/

And a version with threshold and mode included:

function checkVisible(elm, threshold, mode) {
  threshold = threshold || 0;
  mode = mode || 'visible';

  var rect = elm.getBoundingClientRect();
  var viewHeight = Math.max(document.documentElement.clientHeight, window.innerHeight);
  var above = rect.bottom - threshold < 0;
  var below = rect.top - viewHeight + threshold >= 0;

  return mode === 'above' ? above : (mode === 'below' ? below : !above && !below);
}

and with a fiddle to prove it: http://jsfiddle.net/t2L274ty/2/

Box shadow for bottom side only

Specify negative value to spread value. This works for me:

box-shadow: 0 2px 3px -1px rgba(0, 0, 0, 0.1);

Jquery open popup on button click for bootstrap

The answer is on the example link you provided:

http://getbootstrap.com/javascript/#modals-usage

i.e.

Call a modal with id myModal with a single line of JavaScript:

$('#myModal').modal('show');

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

try this=> numpy.array(r) or numpy.array(yourvariable) followed by the command to compare whatever you wish to.

fatal: Unable to create temporary file '/home/username/git/myrepo.git/./objects/pack/tmp_pack_XXXXXX': Permission denied

It sounds like you have file in the git repo owned by root. Since you're ssh'ing in as 'username' to do the push, the files must be writable by username. The easiest thing is probably to create the repo as the user, and use the same user to do your pushes. Another option is to create a group, make everything writable by the group, and make your user a member of that group.

How do I write a RGB color value in JavaScript?

dec2hex = function (d) {
  if (d > 15)
    { return d.toString(16) } else
    { return "0" + d.toString(16) }
}
rgb = function (r, g, b) { return "#" + dec2hex(r) + dec2hex(g) + dec2hex(b) };

and:

parent.childNodes[1].style.color = rgb(155, 102, 102);

On Duplicate Key Update same as insert

I know it's late, but i hope someone will be helped of this answer

INSERT INTO t1 (a,b,c) VALUES (1,2,3),(4,5,6)
ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b);

You can read the tutorial below here :

https://mariadb.com/kb/en/library/insert-on-duplicate-key-update/

http://www.mysqltutorial.org/mysql-insert-or-update-on-duplicate-key-update/

401 Unauthorized: Access is denied due to invalid credentials

Make sure that you enabled anonymous authentication on iis like this:

enter image description here

submit a form in a new tab

Try using jQuery

<script type="text/javascript">
$("form").submit(function() {
$("form").attr('target', '_blank');
return true;
});
</script>

Here is a full answer - http://ftutorials.com/open-html-form-in-new-tab/

Returning an array using C

You can do it using heap memory (through malloc() invocation) like other answers reported here, but you must always manage the memory (use free() function everytime you call your function). You can also do it with a static array:

char* returnArrayPointer() 
{
static char array[SIZE];

// do something in your array here

return array; 
}

You can than use it without worrying about memory management.

int main() 
{
char* myArray = returnArrayPointer();
/* use your array here */
/* don't worry to free memory here */
}

In this example you must use static keyword in array definition to set to application-long the array lifetime, so it will not destroyed after return statement. Of course, in this way you occupy SIZE bytes in your memory for the entire application life, so size it properly!

.setAttribute("disabled", false); changes editable attribute to false

A disabled element is, (self-explaining) disabled and thereby logically not editable, so:

set the disabled attribute [...] changes the editable attribute too

Is an intended and well-defined behaviour.

The real problem here seems to be you're trying to set disabled to false via setAttribute() which doesn't do what you're expecting. an element is disabled if the disabled-attribute is set, independent of it's value (so, disabled="true", disabled="disabled" and disabled="false" all do the same: the element gets disabled). you should instead remove the complete attribute:

element.removeAttribute("disabled");

or set that property directly:

element.disabled = false;

IntelliJ: Error:java: error: release version 5 not supported

Took me a while to aggregate an actual solution, but here's how to get rid of this compile error.

  1. Open IntelliJ preferences.

  2. Search for "compiler" (or something like "compi").

  3. Scroll down to Maven -->java compiler. In the right panel will be a list of modules and their associated java compile version "target bytecode version."

  4. Select a version >1.5. You may need to upgrade your jdk if one is not available.

enter image description here

Java: Local variable mi defined in an enclosing scope must be final or effectively final

What you have here is a non-local variable (https://en.wikipedia.org/wiki/Non-local_variable), i.e. you access a local variable in a method an anonymous class.

Local variables of the method are kept on the stack and lost as soon as the method ends, however even after the method ends, the local inner class object is still alive on the heap and will need to access this variable (here, when an action is performed).

I would suggest two workarounds : Either you make your own class that implements actionlistenner and takes as constructor argument, your variable and keeps it as an class attribute. Therefore you would only access this variable within the same object.

Or (and this is probably the best solution) just qualify a copy of the variable final to access it in the inner scope as the error suggests to make it a constant:

This would suit your case since you are not modifying the value of the variable.