12.set数据结构

1、Set定义

Set数据结构类似于数组，但它成员是唯一不重复的，常用Set定义：

    <script>
        const arrays = [1,2,3,4,5,6,7];
        arrays.push(8);
        arrays.push(1);
        const set = new Set();  
        arrays.forEach(item=>{
            set.add(item);
        });
        const set2 = new Set(arrays);
        console.log(set2);
        const set3 = new Set([1,2,3,4,5,6,7,8]);
        console.log(set3);
        const setStr = new Set("abcdefg");
        console.log(setStr);
    </script>

2、Set属性

    <script>
        const setStr = new Set("aabbccddeeffgg");
        console.log(setStr.size);       //size返回成员总数
    </script>

3、Set方法

    <script>
        const setStr = new Set("aabbccddeeffgg");
        setStr.add("aaa");              //添加元素
        setStr.delete("a");             //删除元素
        console.log(setStr.has("b"));   //是否包含某个元素
        setStr.clear();                 //清除元素
        console.log(setStr);
    </script>

4、Set扩展

    <script>
        const set3 = new Set([1, 2, 3, 4, 5, 6, 7, 8]);
        console.log(set3);
        console.log(...set3);
        console.log([...set3]);
    </script>

5、set对字符串去重

    <script>
        const setStr = new Set("aabbccddeeffgg");
        var str = [...setStr].join("");
        console.log(str);
    </script>