Node.isConnected polyfill for EdgeHTML

node.isConnected-polyfill.js

/*
 * Node.isConnected polyfill for EdgeHTML
 * 2021-04-12
 *
 * 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
        )
      );
    },
  });
}

Isn't contains basically the opposite of isConnected?

This should be much simpler to polyfill - just grab the ownerDocument (which is available as soon as you call document.createElement - documents can own nodes before they actually get inserted) and see if it contains the element:

Object.defineProperty(Node.prototype, "isConnected", {
  get() {
    return this.ownerDocument.contains(this);
  }
});

Seems to work well enough? 🙂

@mindplay-dk Sorry, I missed your question. I think compareDocumentPosition() may be more efficient than contains(). I made this polyfill originally to be used in a performance-sensitive code path.

Also, ownerDocument can be null for some Nodes, e.g. document.ownerDocument === null (document is a Node), so your implementation would break in that case.

Wouldn't a connected element always have a parentNode? (unless of course it's a root element)

Wouldn't a connected element always have a parentNode? (unless of course it's a root element)

Depends on your definition of "connected". If it's a childnode within a subtree that's not connected, it does have a parentNode - but it's still not "connected" within the Document.