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document.getElementsByClassName

Returns an array-like object of all child elements which have all of the given class names. When called on the document object, the complete document is searched, including the root node. You may also call getElementsByClassName() on any element; it will return only elements which are descendants of the specified root element with the given class names.

Syntax

var elements = document.getElementsByClassName(names); // or:
var elements = rootElement.getElementsByClassName(names);
  • elements is a live HTMLCollection of found elements.
  • names is a string representing the list of class names to match; class names are separated by whitespace
  • getElementsByClassName can be called on any element, not only on the document. The element on which it is called will be used as the root of the search.

Examples

Get all elements that have a class of 'test'

document.getElementsByClassName('test');

Get all elements that have both the 'red' and 'test' classes

document.getElementsByClassName('red test');

Get all elements that have a class of 'test', inside of an element that has the ID of 'main'

document.getElementById('main').getElementsByClassName('test');

We can also use methods of Array.prototype on any HTMLCollection by passing the HTMLCollection as the method's this value. Here we'll find all div elements that have a class of 'test':

var testElements = document.getElementsByClassName('test');
var testDivs = Array.prototype.filter.call(testElements, function(testElement){
    return testElement.nodeName === 'DIV';
});

Get class is test elements

This is the most commonly used method of operation

<!doctype html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <div id="parent-id">
        <p>hello word1</p>
        <p class="test">hello word2</p>
        <p >hello word3</p>
        <p>hello word4</p>
    </div>
    <script>
        var parentDOM = document.getElementById("parent-id");
        
        var test=parentDOM.getElementsByClassName("test");//test is not target element
        console.log(test);//HTMLCollection[1]

        var testTarget=parentDOM.getElementsByClassName("test")[0];//year , this element is target
        console.log(testTarget);//<p class="test">hello word2</p>
    </script>
</body>
</html>

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) 3.0 9.0 (Yes) (Yes)
Feature Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support ? (Yes) ? ? ? ?

Specification

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/document/getElementsByClassName