https://wiki-to-yes.org/public/generated/js/vendor_dist/@popperjs/core/dist/esm/dom-utils/contains.js

1import { isShadowRoot } from "./instanceOf.js";
2export default function contains(parent, child) {
3  var rootNode = child.getRootNode && child.getRootNode(); // First, attempt with faster native method
4
5  if (parent.contains(child)) {
6    return true;
7  } // then fallback to custom implementation with Shadow DOM support
8  else if (rootNode && isShadowRoot(rootNode)) {
9      var next = child;
10
11      do {
12        if (next && parent.isSameNode(next)) {
13          return true;
14        } // $FlowFixMe[prop-missing]: need a better way to handle this...
15
16
17        next = next.parentNode || next.host;
18      } while (next);
19    } // Give up, the result is false
20
21
22  return false;
23}