The Element method getElementsByClassName() returns a live HTMLCollection which contains every descendant element which has the specified class name or names.

The method getElementsByClassName() on the Document interface works essentially the same way, except it acts on the entire document, starting at the document root.

Syntax

var elements = element.getElementsByClassName(names);

Parameters

names
A DOMString containing one or more class names to match on, separated by whitespace.

Return value

An HTMLCollection providing a live-updating list of every element which is a member of every class in names.

Usage notes

As always, the returned collection is live, meaning that it always reflects the current state of the DOM tree rooted at the element on which the function was called. As new elements that match names are added to the subtree, they immediately appear in the collection. Similarly, if an existing element that doesn't match names has its set of classes adjusted so that it matches, it immediately appears in the collection.

The opposite is also true; as elements no longer match the set of names, they are immediately removed from the collection.

In quirks mode, the class names are compared in a case-insensitive fashion. Otherwise, they're case sensitive.

Examples

Matching a single class

To look for elements that include among their classes a single specified class, we just provide that class name when calling getElementsByClassName():

element.getElementsByClassName('test');

This example finds all elements that have a class of test, which are also a descendant of the element that has the id of main:

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

Matching multiple classes

To find elements whose class lists include both the red and test classes:

element.getElementsByClassName('red test');

Examining the results

You can use either the item() method on the returned HTMLCollection or standard array syntax to examine individual elements in the collection. However the following code will not work as one might expect because "matches" will change as soon as any "colorbox" class is removed.

var matches = element.getElementsByClassName('colorbox');

for (var i=0; i<matches.length; i++) {
  matches[i].classList.remove('colorbox');
  matches.item(i).classList.add('hueframe');
}

Instead, use another method, such as:

var matches = element.getElementsByClassName('colorbox');

while (matches.length > 0) {
  matches.item(0).classList.add('hueframe');
  matches[0].classList.remove('colorbox');
}

This code finds descendant elements with the "colorbox" class, adds the class "hueframe", by calling item(0), then removes "colorbox" (using array notation). Another element (if any are left) will then become item(0).

Filtering the results using array methods

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';
});

Specifications

Specification Status Comment
DOM
The definition of 'Element.getElementsByClassName()' in that specification.
Living Standard Initial definition

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic supportChrome Full support YesEdge ? Firefox Full support Yes
Notes
Full support Yes
Notes
Notes Prior to Firefox 19, this method was returning a NodeList; it was then changed to reflect the change in the spec.
IE Full support 9Opera Full support YesSafari Full support Yes
Notes
Full support Yes
Notes
Notes Safari on iOS 8 and OS X 10.10 returns a NodeList.
WebView Android ? Chrome Android ? Edge Mobile ? Firefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android ?

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown
See implementation notes.
See implementation notes.

Document Tags and Contributors

Last updated by: fscholz,