This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.
clear() method used to remove all elements from a
WeakSet object, but is no longer part of ECMAScript and its
var ws = new WeakSet(); ws.add(window); ws.has(window); // true ws.clear(); ws.has(window); // false
Not part of any standard.
BCD tables only load in the browser