code: function(key){
            if(!isObject(key))return false;
            if(!isExtensible(key))return frozenStore(this)['delete'](key);
            return $has(key, WEAK) && $has(key[WEAK], this._i) && delete key[WEAK][this._i];
          }
docs: 23.3.3.2 WeakMap.prototype.delete(key) 23.4.3.3 WeakSet.prototype.delete(value)