test14.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div id="mydiv"></div>
<p></p>
<script>
//    Set和Map数据结构
/***Set的成员是唯一的*****/
    const s = new Set();
    var ary = [1,23,3,12,32,42,1,23];
    ary.forEach(x=>s.add(x));
    for(let i of s){
        console.log(i);
    }
//    数组去重的新方法
    console.log([...new Set(ary)]);
//    alert(s.size)
    let a =new Set([1,2,4,6,7]);
    let b =new Set([2,5,6,7,12,42]);
    let ab = new Set([...a,...b]);
    function  showXX(A) {
        return b.has(A);
    }
    let a_b = new Set([...a].filter(showXX));
    console.log(ab);
    console.log(a_b);
//    Map结构
    const mydiv = document.getElementById("mydiv");
//    const data = {};
//    data[mydiv] = "mydiv";
//    alert(data[mydiv])
    var data = new Map();
//    set(key,value),设置键名对应的的键值为value，然后返回整个map结构，所以可以链式操作
    data.set(mydiv,"mydiv")
        .set(1,"a")
        .set(2,"b")
        .set(3,"c")
    console.log(data);
//    data[mydiv] = "mydiv";
    var x = data.get(mydiv);
    var y = new Object({
        name:"1",
        sex:"2"
    });
    console.log(x);
    console.log([...data.values()])

//总之，WeakMap的专用场合就是，它的键所对应的对象，可能会在将来消失。WeakMap结构有助于防止内存泄漏。
    const weakMap = new WeakMap();
    weakMap.set(y,2);
    console.log(weakMap);

</script>
</body>
</html>