code: function has(key) {
                                  if (!isObject(key)) return false;
                                  var data = getWeak(key);
                                  if (data === true) return uncaughtFrozenStore(this).has(key);
                                  return data && $has(data, this._i);
                              }
docs: 23.3.3.4 WeakMap.prototype.has(key) 23.4.3.4 WeakSet.prototype.has(value)