jQuery API

.addClass()

Categories: Attributes | Manipulation > Class Attribute | CSS

.addClass( className ) Returns: jQuery

Description: Adds the specified class(es) to each of the set of matched elements.

  • version added: 1.0.addClass( className )

    classNameOne or more class names to be added to the class attribute of each matched element.

  • version added: 1.4.addClass( function(index, class) )

    function(index, class)A function returning one or more space-separated class names to be added. Receives the index position of the element in the set and the old class value as arguments.

It's important to note that this method does not replace a class. It simply adds the class, appending it to any which may already be assigned to the elements.

More than one class may be added at a time, separated by a space, to the set of matched elements, like so:

$('p').addClass('myClass yourClass');

This method is often used with .removeClass() to switch elements' classes from one to another, like so:

$('p').removeClass('myClass noClass').addClass('yourClass');

Here, the myClass and noClass classes are removed from all paragraphs, while yourClass is added.

As of jQuery 1.4, the .addClass() method allows us to set the class name by passing in a function.

$('ul li:last').addClass(function() {
  return 'item-' + $(this).index();
});

Given an unordered list with five <li> elements, this example adds the class "item-4" to the last <li>.

Examples:

Example: Adds the class 'selected' to the matched elements. 

<!DOCTYPE html>
<html>
<head>
  <style>

  p { margin: 8px; font-size:16px; }
  .selected { color:blue; }
  .highlight { background:yellow; }
  </style>
  <script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body>
	<p>Hello</p>
  <p>and</p>
  <p>Goodbye</p>
<script>$("p:last").addClass("selected");</script>
</body>
</html>

Demo:

Example: Adds the classes 'selected' and 'highlight' to the matched elements. 

<!DOCTYPE html>
<html>
<head>
  <style>

  p { margin: 8px; font-size:16px; }
  .selected { color:red; }
  .highlight { background:yellow; }
  </style>
  <script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body>
	<p>Hello</p>
  <p>and</p>
  <p>Goodbye</p>
<script>$("p:last").addClass("selected highlight");</script>
</body>
</html>

Demo:

Comments

  • Support requests, bug reports, and off-topic comments will be deleted without warning.

  • Please do post corrections or additional examples for .addClass() below. We aim to quickly move corrections into the documentation.
  • If you need help, post at the forums or in the #jquery IRC channel.
  • Report bugs on the bug tracker or the jQuery Forum.
  • Discussions about the API specifically should be addressed in the Developing jQuery Core forum.
  • Rodrigo
    Isn't there a "setClass" function to simply remove all element classes and set it a new one?
  • Rodrigo
    I just realize that I can use $(selector).attr('class','newClass');
  • Yep. You can also use $(selector).removeClass().addClass('newClass');
  • In 1.3 and forward, addClass won't add a class which is already present, to avoid adding redundant classes (e.g. it won't give you class="foo bar foo"). Was this true back in version 1.0? Just mildly curious.
  • It was true as far back as I can remember. Pretty sure it was true even as of 1.0.4.