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    <script>
      /**
       * set 类似于es6新增的特性 类似于数组
       * set 可以使用for of 和 扩展运算符
       * size 返回集合中的元素个数
       * add() 向集合中添加元素 并返回添加的集合
       * delete() 删除元素 返回布尔值
       * has() 判断当前集合中是否包含当前元素  并返回布尔值
       * clear() 清空当前集合 返回的是undefined
       */
      let s = new Set();
      console.log(s);
      let s1 = new Set([1, 2, 3, 4, 5, 6, 7]);
      console.log(s1, "s1");
      console.log(s1.size);
      //console.log(s1.add(13));
      s1.add(13);
      console.log(s1);
      console.log(s1.delete(15));
      s1.delete(15);
      console.log(s1);
      console.log(s1.has(14));
      console.log(s1);
      console.log(s1.clear());
      s1.clear();
      console.log(s1);

      var arr = [12,23,34,45,56,78];
      var s2 = new Set(arr);
      console.log(s2,'s2');
      var s3 = Array.from(s2);
      console.log(s3,'s3');

      //去重
      var list = [12,23,3245,32,23,66,57,78,76,57,3245];
      function reducer(arr) {
        var a1 = new Set(arr);
        return Array.from(a1);
      }
      console.log(reducer(list))
    </script>
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