The Element.attachShadow()
method attaches a shadow DOM tree to the specified element and returns a reference to its ShadowRoot
.
Elements you can attach a shadow to
Note that you can't attach a shadow root to every type of element. There are some that can't have a shadow DOM for security reasons (for example <a>
), and more besides. The following is a list of elements you can attach a shadow root to:
- Any autonomous custom element with a valid name
<article>
<aside>
<blockquote>
<body>
<div>
<footer>
<h1>
<h2>
<h3>
<h4>
<h5>
<h6>
<header>
<main>
<nav>
<p>
<section>
<span>
Syntax
var shadowroot = element.attachShadow(shadowRootInit);
Parameters
shadowRootInit
- A
ShadowRootInit
dictionary, which can contain the following fields:mode
A string specifying the encapsulation mode for the shadow DOM tree. This can be one of:
open
: Elements of the shadow root are accessible from JavaScript outside the root, for example usingElement.shadowRoot
:element.shadowRoot; // Returns a ShadowRoot obj
closed
: Denies access to the node(s) of a closed shadow root from JavaScript outside it:element.shadowRoot; // Returns null
delegatesFocus
- A boolean that, when set to
true
, specifies behavior that mitigates custom element issues around focusability. When a non-focusable part of the shadow DOM is clicked, the first focusable part is given focus, and the shadow host is given any available:focus
styling.
Return value
Returns a ShadowRoot
object.
Exceptions
Exception | Explanation |
---|---|
InvalidStateError
|
The element you are trying to attach to is already a shadow host. |
NotSupportedError
|
You are trying to attach a shadow root to an element outside the HTML namespace, or the element cannot have a shadow attached to it (see above). |
Examples
The following example is taken from our word-count-web-component demo ([[../../../../../../../mdn.github.io/web-components-examples/word-count-web-component/index|see it live also]]). You can see that we use attachShadow()
in the middle of the code to create a shadow root, which we then attach our custom element's contents to.
// Create a class for the element
class WordCount extends HTMLParagraphElement {
constructor() {
// Always call super first in constructor
super();
// count words in element's parent element
var wcParent = this.parentNode;
function countWords(node){
var text = node.innerText || node.textContent
return text.trim().split(/\s+/g).length;
}
var count = 'Words: ' + countWords(wcParent);
// Create a shadow root
var shadow = this.attachShadow({mode: 'open'});
// Create text node and add word count to it
var text = document.createElement('span');
text.textContent = count;
// Append it to the shadow root
shadow.appendChild(text);
// Update count when element content changes
setInterval(function() {
var count = 'Words: ' + countWords(wcParent);
text.textContent = count;
}, 200)
}
}
// Define the new element
customElements.define('word-count', WordCount, { extends: 'p' });
Specifications
Specification | Status | Comment |
---|---|---|
DOMThe definition of 'attachShadow()' in that specification. | Living Standard |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Update compatibility data on GitHub
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
attachShadow
|
Chrome
Full support 53 |
Edge
Full support 79 |
Firefox Full support 63 Full support 63 No support 59 — 63 Disabled' From version 59 until version 63 (exclusive): this feature is behind the |
IE
No support No |
Opera
Full support 40 |
Safari
Full support 10 |
WebView Android
Full support 53 |
Chrome Android
Full support 53 |
Firefox Android Full support 63 Full support 63 No support 59 — 63 Disabled' From version 59 until version 63 (exclusive): this feature is behind the |
Opera Android
Full support 41 |
Safari iOS
Full support 10 |
Samsung Internet Android
Full support 6.0 |
|
Chrome
Full support Yes |
Edge
Full support 79 |
Firefox
No support No |
IE
No support No |
Opera
? |
Safari
? |
WebView Android
Full support Yes |
Chrome Android
Full support Yes |
Firefox Android
No support No |
Opera Android
? |
Safari iOS
? |
Samsung Internet Android
Full support Yes |
Legend
- Full support
- Full support
- No support
- No support
- Compatibility unknown
- Compatibility unknown
- Experimental. Expect behavior to change in the future.'
- Experimental. Expect behavior to change in the future.
- Non-standard. Expect poor cross-browser support.'
- Non-standard. Expect poor cross-browser support.
- User must explicitly enable this feature.'
- User must explicitly enable this feature.
Element.attachShadow() by Mozilla Contributors is licensed under CC-BY-SA 2.5.