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DOMTokenList

The DOMTokenList interface represents a set of space-separated tokens. Such a set is returned by Element.classList, HTMLLinkElement.relList, HTMLAnchorElement.relList, HTMLAreaElement.relList, HTMLIframeElement.sandbox, or HTMLOutputElement.htmlFor. 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: 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 + '"';