Node.isConnected - Web APIs 编辑

The isConnected read-only property of the Node interface returns a boolean indicating whether the node is connected (directly or indirectly) to the context object, for example the Document object in the case of the normal DOM, or the ShadowRoot in the case of a shadow DOM.

Syntax

var isItConnected = nodeObjectInstance.isConnected

Return value

A Boolean that is true if the node is connected to its relevant context object, and false if not.

Examples

Standard DOM

A standard DOM example:

let test = document.createElement('p');
console.log(test.isConnected); // Returns false
document.body.appendChild(test);
console.log(test.isConnected); // Returns true

Shadow DOM

A shadow DOM example:

// Create a shadow root
var shadow = this.attachShadow({mode: 'open'});

// Create some CSS to apply to the shadow dom
var style = document.createElement('style');
console.log(style.isConnected); // returns false

style.textContent = `
.wrapper {
  position: relative;
}

.info {
  font-size: 0.8rem;
  width: 200px;
  display: inline-block;
  border: 1px solid black;
  padding: 10px;
  background: white;
  border-radius: 10px;
  opacity: 0;
  transition: 0.6s all;
  positions: absolute;
  bottom: 20px;
  left: 10px;
  z-index: 3
}
`;

// Attach the created style element to the shadow dom

shadow.appendChild(style);
console.log(style.isConnected); // Returns true

Polyfill

Node.isConnected can be polyfilled with the following code for IE10 and EdgeHTML:

/*
 * Node.isConnected polyfill for IE and EdgeHTML
 * 2020-02-04
 *
 * By Eli Grey, https://eligrey.com
 * Public domain.
 * NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
 */

if (!('isConnected' in Node.prototype)) {
  Object.defineProperty(Node.prototype, 'isConnected', {
    get() {
      return (
        !this.ownerDocument ||
        !(
          this.ownerDocument.compareDocumentPosition(this) &
          this.DOCUMENT_POSITION_DISCONNECTED
        )
      );
    },
  });
}

Specifications

Browser compatibility

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