es6之模拟set

class Myset {
      constructor(iterator) {
        if (typeof iterator[Symbol.iterator] != "function") {
          throw new TypeError(" object is not iterable (cannot read property Symbol(Symbol.iterator))")
        }
        this._data = [];
        for (var item of iterator) {
          this.add(item);
        }
      }
      
      get size(){//没有set,因为该属性是只读的
        return this._data.length;
      }
      add(item) {
        if (this.has(item)) {
          return;
        }
        this._data.push(item)
      }

      delete(item){
        var index = this._data.findIndex(ele=>ele == item);
        if(index < 0){
          return false;
        }  
        this._data.splice(index,1);
        return true;
      }

      has(item) {
        if (this._data.indexOf(item) < 0) {
          return false;
        }
        return true;
      }

      *[Symbol.iterator](){ //能够用for of循环
        for( var item of this._data){
          yield item;
        }
      }

    }
    var myset = new Myset([1, 23, 4])