DOMTokenList

The DOMTokenList interface represents a set of space-separated tokens. Such a set is returned by Element.classList, HTMLLinkElement.relList, HTMLAnchorElement.relList or HTMLAreaElement.relList. It is indexed beginning with 0 as with JavaScript Array objects. DOMTokenList is always case-sensitive.

Properties

DOMTokenList.length Read only

Is an integer representing the number of objects stored in the object.

DOMTokenList.value Read only

Returns the value of the list as a DOMString.

Methods

DOMTokenList.item()

Returns an item in the list by its index (returns undefined if the number is greater than or equal to the length of the list).

DOMTokenList.contains()

Returns true if the list contains the given token, otherwise false.

DOMTokenList.add()

Adds the given token to the list.

DOMTokenList.remove()

Removes the specified token from the list.

DOMTokenList.replace()

Replaces an existing token with a new token.

DOMTokenList.supports()

Returns true if a given token is in the associated attribute's supported tokens.

DOMTokenList.toggle()

Removes a given token from the list and returns false. If token doesn't exist it's added and the function returns true.

DOMTokenList.entries()

Returns an iterator allowing you to go through all key/value pairs contained in this object.

DOMTokenList.forEach()

Executes a provided function once per DOMTokenList element.

DOMTokenList.keys()

Returns an iterator allowing you to go through all keys of the key/value pairs contained in this object.

DOMTokenList.values()

Returns an iterator allowing you to go through all values of the key/value pairs contained in this object.

Examples

In the following simple example we retrieve the list of classes set on a <p> element as a DOMTokenList using Element.classList, add a class using DOMTokenList.add(), and then update the Node.textContent of the <p> to equal the DOMTokenList.

First, the HTML:

<p class="a b c"></p>

Now the JavaScript:

var para = document.querySelector("p");
var classes = para.classList;
para.classList.add("d");
para.textContent = 'paragraph classList is "' + classes + '"';

The output looks like this:

Trimming of whitespace and removal of duplicates

Methods that modify the DOMTokenList (such as DOMTokenList.add()) automatically trim any excess whitespace and remove duplicate values from the list. For example:

<span class="    d   d e f"></span>

var span = document.querySelector("span");
var classes = span.classList;
span.classList.add("x");
span.textContent = 'span classList is "' + classes + '"';

The output looks like this:

Specifications

Browser compatibility

[1] IE only trims whitespace — it doesn't remove duplicates.

See Also

• DOMSettableTokenList (object that extends DOMTokenList with settable .value property)