Node.getRootNode() - Web APIs 编辑

The getRootNode() method of the Node interface returns the context object's root, which optionally includes the shadow root if it is available.

Syntax

var root = node.getRootNode(options);

Parameters

options Optional

An object that sets options for getting the root node. The available options are:

• composed: A Boolean that indicates whether the shadow root should be returned (false, the default), or a root node beyond shadow root (true).

Returns

An object inheriting from Node. This will differ in exact form depending on where you called getRootNode(); for example:

• Calling it on an element inside a standard web page will return an HTMLDocument object representing the entire page.
• Calling it on an element inside a shadow DOM will return the associated ShadowRoot.

Examples

The first simple example returns a reference to the HTML/document node:

rootNode = node.getRootNode();

This more complex example shows the difference between returning a normal root, and a root incuding the shadow root. (See the full source code):

<!-- source: https://github.com/jserz/js_piece/blob/master/DOM/Node/getRootNode()/demo/getRootNode.html -->
<div class="js-parent">
  <div class="js-child"></div>
</div>
<div class="js-shadowHost"></div>
<script>
  // works on Chrome 54+, Opera 41+

  var parent = document.querySelector('.js-parent'),
      child = document.querySelector('.js-child'),
      shadowHost = document.querySelector('.js-shadowHost');

  console.log(parent.getRootNode().nodeName); // #document
  console.log(child.getRootNode().nodeName); // #document

  // create a ShadowRoot
  var shadowRoot = shadowHost.attachShadow({mode:'open'});
  shadowRoot.innerHTML = '<style>div{background:#2bb8aa;}</style>'
      + '<div class="js-shadowChild">content</div>';
  var shadowChild = shadowRoot.querySelector('.js-shadowChild');

  // The default value of composed is false
  console.log(shadowChild.getRootNode() === shadowRoot); // true
  console.log(shadowChild.getRootNode({composed:false}) === shadowRoot); // true
  console.log(shadowChild.getRootNode({composed:true}).nodeName); // #document
</script>

Specifications

Browser compatibility

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