I need to choose some elements from the given list, knowing their index. Let say I would like to create a new list, which contains element with index 1, 2, 5, from given list [-2, 1, 5, 3, 8, 5, 6]. What I did is:

    a = [-2,1,5,3,8,5,6]
    b = [1,2,5]
    c = [ a[i] for i in b]
Is there any better way to do it? something like c = a[b] ?


Access multiple elements of list knowing their index

In Javascript, I&#39;m trying to take an initial array of number values and count the elements inside it. Ideally, the result would be two new arrays, the first specifying each unique element, and the second containing the number of times each element occurs. However, I&#39;m open to suggestions on the format of the output.

For example, if the initial array was:

    5, 5, 5, 2, 2, 2, 2, 2, 9, 4

Then two new arrays would be created. The first would contain the name of each unique element:

    5, 2, 9, 4

The second would contain the number of times that element occurred in the initial array:

    3, 5, 1, 1

Because the number 5 occurs three times in the initial array, the number 2 occurs five times and 9 and 4 both appear once.

I&#39;ve searched a lot for a solution, but nothing seems to work, and everything I&#39;ve tried myself has wound up being ridiculously complex. Any help would be appreciated!

Thanks :)

Counting the occurrences / frequency of array elements

I&#39;m brand new to jQuery and have some experience using Prototype. In Prototype, there is a method to &quot;flash&quot; an element &amp;mdash; ie. briefly highlight it in another color and have it fade back to normal so that the user&#39;s eye is drawn to it. Is there such a method in jQuery? I see fadeIn, fadeOut, and animate, but I don&#39;t see anything like &quot;flash&quot;. Perhaps one of these three can be used with appropriate inputs?

How do you make an element &quot;flash&quot; in jQuery

Say I have this:

    &lt;div class=&quot;class1 class2&quot;&gt;&lt;/div&gt;

How do I select this `div` element?

    document.getElementsByClassName(&#39;class1&#39;)[0].getElementsByClassName(&#39;class2&#39;)[0]

That does not work.

I know that, in jQuery, it is `$(&#39;.class1.class2&#39;)`, but I&#39;d like to select it with vanilla JavaScript.

How to get elements with multiple classes

I need a quick algorithm to select 5 random elements from a generic list. For example, I&#39;d like to get 5 random elements from a `List&lt;string&gt;`.


Select N random elements from a List&lt;T&gt; in C#

Is there any fast (and nice looking) way to remove an element from an array in Java?

Removing an element from an Array (Java)

 1. What is the most efficient way to check if an array is **a flat array
    of primitive values** or if it is a **multidimensional array**?
 2. Is there any way to do this without actually looping through an
    array and running `is_array()` on each of its elements?

Checking if array is multidimensional or not?

I have two lists with different objects in them.

    List&lt;Object1&gt; list1;
    List&lt;Object2&gt; list2;

I want to check if element from list1 exists in list2, based on specific attribute (Object1 and Object2 have (among others),  one mutual attribute (with type Long), named attributeSame).

right now, I do it like this:

    boolean found = false;
    for(Object1 object1 : list1){
       for(Object2 object2: list2){
           if(object1.getAttributeSame() == object2.getAttributeSame()){
               found = true;
               //also do something
           }
        }
        if(!found){
            //do something
        }
        found = false;
    }
But I think there is a better and faster way to do this :)
Can someone propose it?

Thanks!

Check if one list contains element from the other

Is it possible to set width or height of HTML element (ex. `&lt;div&gt;`) in JavaScript in Standards Mode?

Note the following code:

    &lt;html&gt;
    &lt;script language=&quot;javascript&quot; type=&quot;text/javascript&quot;&gt;
        function changeWidth(){
            var e1 = document.getElementById(&quot;e1&quot;);
            e1.style.width = 400;
        } 
    &lt;/script&gt;
    &lt;body&gt;
        &lt;input type=&quot;button&quot; value=&quot;change width&quot; onclick=&quot;changeWidth()&quot;/&gt;
        &lt;div id=&quot;e1&quot; style=&quot;width:20px;height:20px; background-color:#096&quot;&gt;&lt;/div&gt;
    &lt;/body&gt;
    &lt;/html&gt;

When user presses the _change width_ button, the `&lt;div&gt;`&#39;s width should change.

It works fine when doctype declaration determines Quirks Mode. In Standards Mode I&#39;m unable to change the element&#39;s size this way

Is it possible to manipulate the size of an element in Standards Mode? How to bypass this disfunctionality?


Set element width or height in Standards Mode

Is there a default method defined in .Net for C# to remove all the elements within a list which are `null`?

    List&lt;EmailParameterClass&gt; parameterList = new List&lt;EmailParameterClass&gt;{param1, param2, param3...};

Let&#39;s say some of the parameters are `null`; I cannot know in advance and I want to remove them from my list so that it only contains parameters which are not null.



How to remove all the null elements inside a generic list in one go?

Is there a way to get (from somewhere) the number of elements in a Javascript object?? (i.e. constant-time complexity).

I can&#39;t find a property or method that retrieves that information. So far I can only think of doing an iteration through the whole collection, but that&#39;s linear time.  
It&#39;s strange there is no direct access to the size of the object, don&#39;t you think.

**EDIT:**  
I&#39;m talking about the `Object` object (not objects in general):

```
var obj = new Object ;
```




Number of elements in a javascript object

How do you test an element for existence without the use of the `getElementById` method?

I have set up a [live demo][1] for reference. I will also print the code on here as well:

    &lt;!DOCTYPE html&gt;
    &lt;html&gt;
    &lt;head&gt;
        &lt;script&gt;
        var getRandomID = function (size) {
                var str = &quot;&quot;,
                    i = 0,
                    chars = &quot;0123456789abcdefghijklmnopqurstuvwxyzABCDEFGHIJKLMNOPQURSTUVWXYZ&quot;;
                while (i &lt; size) {
                    str += chars.substr(Math.floor(Math.random() * 62), 1);
                    i++;
                }
                return str;
            },
            isNull = function (element) {
                var randomID = getRandomID(12),
                    savedID = (element.id)? element.id : null;
                element.id = randomID;
                var foundElm = document.getElementById(randomID);
                element.removeAttribute(&#39;id&#39;);
                if (savedID !== null) {
                    element.id = savedID;
                }
                return (foundElm) ? false : true;
            };
        window.onload = function () {
            var image = document.getElementById(&quot;demo&quot;);
            console.log(&#39;undefined&#39;, (typeof image === &#39;undefined&#39;) ? true : false); // false
            console.log(&#39;null&#39;, (image === null) ? true : false); // false
            console.log(&#39;find-by-id&#39;, isNull(image)); // false
            image.parentNode.removeChild(image);
            console.log(&#39;undefined&#39;, (typeof image === &#39;undefined&#39;) ? true : false); // false ~ should be true?
            console.log(&#39;null&#39;, (image === null) ? true : false); // false ~ should be true?
            console.log(&#39;find-by-id&#39;, isNull(image)); // true ~ correct but there must be a better way than this?
        };
        &lt;/script&gt;
    &lt;/head&gt;
    &lt;body&gt;
        &lt;div id=&quot;demo&quot;&gt;&lt;/div&gt;
    &lt;/body&gt;
    &lt;/html&gt;

Basically the above code demonstrates an element being stored into a variable and then removed from the DOM. Even though the element has been removed from the DOM, the variable retains the element as it was when first declared. In other words, it is not a live reference to the element itself, but rather a replica. As a result, checking the variable&#39;s value (the element) for existence will provide an unexpected result.

The `isNull` function is my attempt to check for an elements existence from a variable, and it works, but I would like to know if there is an easier way to accomplish the same result.

PS: I&#39;m also interested in why JavaScript variables behave like this if anyone knows of some good articles related to the subject.

  [1]: http://jsbin.com/apawi5/3





How can I check if an element exists in the visible DOM?

I have two `ArrayList` objects with three integers each. I want to find a way to return the common elements of the two lists. Has anybody an idea how I can achieve this? 

Common elements in two lists

Javascript: I have the DOM representation of a node (element or document) and I&#39;m looking for the string representation of it. E.g.,

    var el = document.createElement(&quot;p&quot;);
    el.appendChild(document.createTextNode(&quot;Test&quot;));

should yield:

    get_string(el) == &quot;&lt;p&gt;Test&lt;/p&gt;&quot;;

I have the strong feeling, that I&#39;m missing something trivially simple, but I just don&#39;t find a method that works in IE, FF, Safari and Opera. Therefore, outerHTML is no option.

Get the string representation of a DOM node

How can i find the next element by class.

i tried with `$(obj).next(&#39;.class&#39;);` but this returns classes only in `$(obj)` parent. 
I need to take the next element anywhere throughout the code by class name.
Because my code looks like 

    &lt;table&gt;
    &lt;tr&gt;&lt;td&gt;&lt;div class=&quot;class&quot;&gt;First&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
    &lt;tr&gt;&lt;td&gt;&lt;div class=&quot;class&quot;&gt;Second&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
    &lt;/table&gt;

Is this possible?

jquery, find next element by class

I have the following `Array = [&quot;Jason&quot;, &quot;Jason&quot;, &quot;Teresa&quot;, &quot;Judah&quot;, &quot;Michelle&quot;, &quot;Judah&quot;, &quot;Judah&quot;, &quot;Allison&quot;]`

How do I produce a count for each **identical element**? 

    Where:
    &quot;Jason&quot; = 2, &quot;Judah&quot; = 3, &quot;Allison&quot; = 1, &quot;Teresa&quot; = 1, &quot;Michelle&quot; = 1?

or **produce a hash** Where:

   Where:
    hash = { &quot;Jason&quot; =&gt; 2, &quot;Judah&quot; =&gt; 3, &quot;Allison&quot; =&gt; 1, &quot;Teresa&quot; =&gt; 1, &quot;Michelle&quot; =&gt; 1 }

How to count identical string elements in a Ruby array

I have been trying to add onclick event to new elements I added with JavaScript.

The problem is when I check document.body.innerHTML I can actually see the onclick=alert(&#39;blah&#39;) is added to the new element.

But when I click that element I don&#39;t see the alert box is working. In fact anything related to JavaScript is not working..

here is what I use to add new element:

    function add_img() { 
      var elemm = document.createElement(&#39;rvml:image&#39;); 
      elemm.src = &#39;blah.png&#39;;
      elemm.className = &#39;rvml&#39;;
      elemm.onclick = &quot;alert(&#39;blah&#39;)&quot;;
      document.body.appendChild(elemm);
      elemm.id = &quot;gogo&quot;;
      elemm.style.position=&#39;absolute&#39;;
      elemm.style.width=55;
      elemm.style.height=55;
      elemm.style.top=200;
      elemm.style.left=300;
      elemm.style.rotation=200; 
    }

Here is how I call this function:

    &lt;button onclick=add_img()&gt;add image&lt;/button&gt;

Now the image draws perfectly inside the browser. But when I click the image I don&#39;t get that alert.


Add onclick event to newly added element in JavaScript

What I&#39;m trying to do is to count all of the elements in the current page with the same class and then I&#39;m going to use it to be added onto a name for an input form. Basically I&#39;m allowing users to click on a `&lt;span&gt;` and then by doing so add another one for more of the same type of items. But I can&#39;t think of a way to count all of these simply with jQuery/JavaScript.

I was going to then name the item as something like `name=&quot;whatever(total+1)&quot;`, if anyone has a simple way to do this I&#39;d be extremely grateful as JavaScript isn&#39;t exactly my native tongue.

jQuery counting elements by class - what is the best way to implement this?

Is there any **difference** between these solutions?

Solution 1:

    

&lt;!-- begin snippet: js hide: false console: true babel: false --&gt;

&lt;!-- language: lang-js --&gt;

    function doSomething(id, value) {
      console.log(value);
      //...
    }

&lt;!-- language: lang-html --&gt;

    &lt;input id=&quot;theId&quot; value=&quot;test&quot; onclick=&quot;doSomething(this.id, this.value)&quot; /&gt;

&lt;!-- end snippet --&gt;

...and Solution 2:

    

&lt;!-- begin snippet: js hide: false console: true babel: false --&gt;

&lt;!-- language: lang-js --&gt;

    function doSomething(id) {
      var value = document.getElementById(id).value;
      console.log(value);
      //...
    }

&lt;!-- language: lang-html --&gt;

    &lt;input id=&quot;theId&quot; value=&quot;test&quot; onclick=&quot;doSomething(this.id)&quot; /&gt;

&lt;!-- end snippet --&gt;

    

Getting DOM element value using pure JavaScript

I&#39;m trying to find an element with `document.querySelector` which has *multiple data-attributes*:

    &lt;div class=&quot;text-right&quot; data-point-id=&quot;7febe088-4eca-493b-8455-385b39ad30e3&quot; data-period=&quot;current&quot;&gt;-&lt;/div&gt;

I thought about something like this:

    document.querySelector(&#39;[data-point-id=&quot;7febe088-4eca-493b-8455-385b39ad30e3&quot;] [data-period=&quot;current&quot;]&#39;)

But it does not work. &lt;br&gt;
However, it works well, if I put the second data-attribute in a child-element like:

    &lt;div class=&quot;text-right&quot; data-point-id=&quot;7febe088-4eca-493b-8455-385b39ad30e3&quot;&gt; &lt;span data-period=&quot;current&quot;&gt;-&lt;/span&gt; &lt;/div&gt;

So, is there an option to search for **both attributes at once**?&lt;br&gt;I&#39;ve tried several options but I don&#39;t get it.

document.querySelector multiple data-attributes in one element

Having a vector `x` and I have to add an element (`newElem`) .

Is there any difference between - 

    x(end+1) = newElem; 

and 

    x = [x newElem];

?



Octave/Matlab: Adding new elements to a vector

This seems like something that would have a quick answer, but I can&#39;t find one. Maybe I&#39;m searching the wrong terms? No libraries please, though I don&#39;t need cross-browser fallbacks, I&#39;m targeting all the latest versions on this project. 

I&#39;m getting some elements:

    element = document.querySelectorAll(&quot;.someselector&quot;);

This is working, but how do I now delete these elements? Do I have to loop through them and do the `element.parentNode.removeChild(element);` thing, or is there a simple function I&#39;m missing?

How to remove elements that were fetched using querySelectorAll?

I&#39;ve seen a lot of different styles (and few different methods) of creating elements in jQuery. I was curious about the **clearest** way to build them, and also if any particular method is objectively better than another for any reason. Below are some *examples* of the styles and methods that I&#39;ve seen.

    var title = &quot;Title&quot;;
    var content = &quot;Lorem ipsum&quot;;
    
    // escaping endlines for a multi-line string
    // (aligning the slashes is marginally prettier but can add a lot of whitespace)
    var $element1 = $(&quot;\
        &lt;div&gt;&lt;h1&gt;&quot; + title + &quot;&lt;/h1&gt;\
            &lt;div class=&#39;content&#39;&gt;  \
            &quot; + content + &quot;        \
            &lt;/div&gt;                 \
        &lt;/div&gt;                     \
    &quot;);
    
    // all in one
    // obviously deficient
    var $element2 = $(&quot;&lt;div&gt;&lt;h1&gt;&quot; + title + &quot;&lt;/h1&gt;&lt;div class=&#39;content&#39;&gt;&quot; + content + &quot;&lt;/div&gt;&lt;/div&gt;&quot;);
    
    // broken on concatenation
    var $element3 = $(&quot;&lt;div&gt;&lt;h1&gt;&quot; +
                    title + 
                    &quot;&lt;/h1&gt;&lt;div class=&#39;content&#39;&gt;&quot; +
                    content +
                    &quot;&lt;/div&gt;&lt;/div&gt;&quot;);
    
    // constructed piecewise
    // (I&#39;ve seen this with nested function calls instead of temp variables)
    var $element4 = $(&quot;&lt;div&gt;&lt;/div&gt;&quot;);
    var $title = $(&quot;&lt;h1&gt;&lt;/h1&gt;&quot;).html(title);
    var $content = $(&quot;&lt;div class=&#39;content&#39;&gt;&lt;/div&gt;&quot;).html(content);
    $element4.append($title, $content);
    
    $(&quot;body&quot;).append($element1, $element2, $element3, $element4);

Please feel free to demonstrate any other methods/styles you might use.

Clearest way to build html elements in jQuery

I have a jQuery element but I have to send it to a function that only accepts HTML elements.  How can I convert the jQuery element to an HTML element?

Convert jquery element to html element

Using jQuery, how can I get the input element that has the caret&#39;s (cursor&#39;s) focus?   

Or in other words, how to determine if an input has the caret&#39;s focus?



How to get the focused element with jQuery?

A while ago I was making some test in JavaScript, 
and played with a code to get the text of all elements with a certain class.
 
Now I was trying to make something like this but obtain all elements by a certain type, for example all elements `type=&quot;text&quot;`

Is there any way to do this in JavaScript or should I use jQuery?


	var xx = document.getElementsByClassName(&quot;class&quot;);
	for (i=0;i&lt;xx.length;i++){
		var str=xx[i].innerHTML;
                alert(str);
	}


Accessing elements by type in JavaScript

How I can get the number of elements in node of JSON data? 

**JSON:**

	{
	  &quot;result&quot;:[
		{
		  &quot;run&quot;:[
			{
			  &quot;action&quot;:&quot;stop&quot;
			},
			{
			  &quot;action&quot;:&quot;start&quot;
			},
			{
			  &quot;action&quot;:&quot;start&quot;
			}
		  ],
		  &quot;find&quot;:true
		}
	  ]
	}

I need to get the number of elements from node `data[&#39;result&#39;][0][&#39;run&#39;]`. It should be 3, but I can&#39;t find how to do it in Python.

How to count items in JSON data

I&#39;m trying this to get the `id` of each element in a `class` but instead it&#39;s alerting each name of the class separately, so for `class=&quot;test&quot;` it&#39;s alerting: `t`, `e`, `s`, `t`... Any advice on how to get the each element `id` that is part of the `class` is appreciated, as I can&#39;t seem to figure this out.. Thanks.

    $.each(&#39;test&#39;, function() { 
       alert(this)
    });

jQuery, get ID of each element in a class using .each?

What is the proper way to loop through literals of an enum in TypeScript?

(I am currently using TypeScript 1.8.1.)

I&#39;ve got the following enum:

    export enum MotifIntervention {
        Intrusion,
        Identification,
        AbsenceTest,
        Autre
    }

    export class InterventionDetails implements OnInit
    {
        constructor(private interService: InterventionService)
        {
            let i:number = 0;
            for (let motif in MotifIntervention) {
                console.log(motif);
            }
        }

The result displayed is a list

    0
    1
    2
    3
    Intrusion,
    Identification,
    AbsenceTest,
    Autre

I do want only four iterations in the loop as there are only four elements in the enum. I don&#39;t want to have 0 1 2 and 3 that seem to be index numbers of the enum.



How can I loop through enum values for display in radio buttons?

How can I reference the script element that loaded the javascript that is currently running?

Here&#39;s the situation. I have a &quot;master&quot; script being loaded high in the page, first thing under the HEAD tag.

    &lt;!DOCTYPE html PUBLIC &quot;-//W3C//DTD XHTML 1.0 Transitional//EN&quot; 
    &quot;http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd&quot;&gt;
    &lt;html xmlns=&quot;http://www.w3.org/1999/xhtml&quot; xml:lang=&quot;en&quot; lang=&quot;en&quot;&gt;
    &lt;head&gt;
    &lt;script type=&quot;text/javascript&quot; src=&quot;scripts.js&quot;&gt;&lt;/script&gt;

There is a script in &quot;scripts.js&quot; which needs to be able to do on-demand loading of other scripts. The normal method doesn&#39;t quite work for me because I need to add new scripts without referencing the HEAD tag, because the HEAD element hasn&#39;t finished rendering:

    document.getElementsByTagName(&#39;head&#39;)[0].appendChild(v);

What I want to do is reference the script element that loaded the current script so that I can then append my new dynamically loaded script tags into the DOM after it.

    &lt;script type=&quot;text/javascript&quot; src=&quot;scripts.js&quot;&gt;&lt;/script&gt;
    loaded by scripts.js--&gt;&lt;script type=&quot;text/javascript&quot; src=&quot;new_script1.js&quot;&gt;&lt;/script&gt;
    loaded by scripts.js --&gt;&lt;script type=&quot;text/javascript&quot; src=&quot;new_script2.js&quot;&gt;&lt;/script&gt;




How may I reference the script tag that loaded the currently-executing script?

I&#39;m wondering what is the fastest way in JavaScript to move an element from the beginning of an `Array` to the end. For example if we have

`[8,1,2,3,4,5,6,7]`

And we want: `[1,2,3,4,5,6,7,8]`

I want to move the first element to the end. I was thinking about switching element 0 with element 1, after that switching element 1 with element 2 and so on until the 8 is at the and (basically how bubblesort works). I was wondering if there is a faster way to bring the first element to the end.

I will be using small Arrays (around 10 elements), and I want to avoid `shift()` since it&#39;s pretty slow.


This is what I have now on chrome it&#39;s 45% faster than normal shift+push: http://jsperf.com/shift-myfunc

The arrays will have objects in them for a game.

Fastest way to move first element to the end of an Array

What is the difference between using [the `delete` operator][1] on the array element as opposed to using [the `Array.splice` method][2]? 

For example:

    myArray = [&#39;a&#39;, &#39;b&#39;, &#39;c&#39;, &#39;d&#39;];

    delete myArray[1];
    //  or
    myArray.splice (1, 1);

Why even have the splice method if I can delete array elements like I can with objects?

  [1]: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Operators/delete
  [2]: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/splice


Deleting array elements in JavaScript - delete vs splice

How can I get the element before the last element from an array in PHP5 ?

PHP - How to get the element before the last element from an array?

Is it possible, using jQuery, to find out the type of an element with jQuery? For example, is the element a div, span, select, or input?

For example, if I am trying to load values into a drop-down list with jQuery, but the same script can generate code into a set of radio buttons, could I create something like:

    $(&#39;.trigger&#39;).live(&#39;click&#39;, function () {
       var elementType = $(this).prev().attr(WHAT IS IT);
    });

Given a drop-down list with a button next to it with the **trigger** class, my `elementType` variable should return `select` upon the button being pressed.

Get element type with jQuery

I am trying to find a span element who has an id in a particular pattern. Its main use is to find certain elements rendered by an asp.net (aspx) page which is derived from a master page.

jquery: find element whose id has a particular pattern

i am getting the following error while loading my index page in FF3.0. Sorry, i am unable to paste the script here as it is 2030 lines of code.

&gt; element.dispatchEvent is not a function

On expansion it gives me below things,

&gt; fire()()prototype.js?1 (line 3972)
&gt; 
&gt; _methodized()()prototype.js?1 (line 246)
&gt; 
&gt; fireContentLoadedEvent()prototype.js?1 (line 4006)
&gt; 
&gt; [Break on this error] element.dispatchEvent(event);

`element.dispatchEvent(event);` is in line 3972 of prototype.js. I am including prototype.js along with 10s of other js files in my index page.

Has anybody came across this kind of error? Please somebody explain me why this error is showing up.

All Element Solutions on Gang of Coders

Total of 36 Element Solutions