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is (attribute)

The is global attribute allows you to specify that a standard HTML element should behave like a defined custom built-in element (see Using custom elements for more details).

This attribute can only be used if the specified custom element name has been successfully defined in the current document, and extends the element type it is being applied to.

Examples

The following code is taken from our word-count-web-component example (see it live also).

// Create a class for the element
class WordCount extends HTMLParagraphElement {
  constructor() {
    // Always call super first in constructor
    super();

    // Constructor contents ommitted for brevity
    ...

  }
}

// Define the new element
customElements.define('word-count', WordCount, { extends: 'p' });
<p is="word-count"></p>

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'is' in that specification.
Living Standard

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
is 67 79 63
63
59 — 63
Disabled
Disabled From version 59 until version 63 (exclusive): this feature is behind the dom.webcomponents.customelements.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.
? — 59
Disabled
Disabled Until version 59 (exclusive): this feature is behind the dom.webcomponents.enabled preference (needs to be set to true) and the dom.webcomponents.customelements.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.
No 55 No
Mobile
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
is 67 67 63
63
59 — 63
Disabled
Disabled From version 59 until version 63 (exclusive): this feature is behind the dom.webcomponents.customelements.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.
? — 59
Disabled
Disabled Until version 59 (exclusive): this feature is behind the dom.webcomponents.enabled preference (needs to be set to true) and the dom.webcomponents.customelements.enabled preference (needs to be set to true). To change preferences in Firefox, visit about:config.
48 No 9.0

See also

© 2005–2020 Mozilla and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/is