code: function WeakMap_constructor(iterable) { // @arg Iterator|Array = null
      this._index = [];
      this._value = [];
  
      var that = this;
  
      if (Array.isArray(iterable)) {
          iterable.forEach(function(value) {
              that["set"](value[0], value[1]);
          });
      } else if (iterable && iterable["next"]) {
          var result = null;
  
          while ( (result = iterable["next"]()) ) {
              if (result["done"]) {
                  break;
              }
              this["set"](result["value"][0], result["value"][1]);
          }
      }
  }
docs: === WeakMap =============================================