ES6中Set和WeakSet

Set(放数组,不能重复)

会自动去重,有4个元素,但是打印出来只有三个
let setArr=new Set(['zhang','huan','eternity','zhang']);
console.log(setArr);//{"zhang", "huan", "eternity"}

//添加元素
setArr.add('zhanghuan');
console.log(setArr);//{"zhang", "huan", "eternity", "zhanghuan"}

//查找元素
setArr.has('zhang');
console.log(setArr.has('zhang'));//true

//删除元素
setArr.delete('huan');//true
console.log(setArr);//{"zhang", "eternity", "zhanghuan"}

//循环打印
for(let item of setArr){
    console.log(item);
}

setArr.forEach(item=>console.log(item));

//长度(属性,不是方法)
setArr.size;

WeakSet(可以放对象,也是不能重复)

let weakObj=new WeakSet();//不能直接放对象,需要添加
let obj={'a':'eternity','b':'zhang'};
weakObj.add(obj);
console.log(weakObj);
let obj1={'a':'eternity','b':'zhang'};
weakObj.add(obj1);
console.log(weakObj);//此时有两个值,因为obj和obj1的内存地址不一样