es6(10)--Set,Map(1)

 //Set
 {
     let list=new Set();
     list.add(5);//添加
     list.add(7);
     //属性size就是长度
     console.log('size',list.size);//
 }
 {
     let arr = [1,2,3,4,5];
     let list = new Set(arr);
     console.log(list.size);//
 }
 {
     //去重
     let list = new Set();
     list.add(1);
     list.add(2);
     list.add(1);
     console.log('size',list);//1,2,没有最后的1

     let arr=[1,2,3,1,2];
     let list2=new Set(arr);
     console.log('unique',list2);//1,2,3,没有后面的1,2
 }
 {
     let arr=['add','delete','clear','has'];
     let list=new Set(arr);
     console.log('has',list.has('add'));//查看是否存在
     console.log('delete',list.delete('add'),list);//删除
     console.log('clear',list.clear('add'),list);//清空
 }
 //遍历
 {
     let arr=['add','delete','clear','has'];
     let list=new Set(arr);

     for(let key of list.keys()){
         console.log('key',key);
     }
     for(let value of list.values()){
         console.log('keys',value);
     }
     for(let [key,value] of list.entries()){
         console.log('entries',key,value);
     }
     list.forEach(function(item){
         console.log(item)
     })
 }
 //WeakSet:元素只能是对象，不能是数值，不能遍历，没有clear方法，没有set属性
 {
     let weakList=new WeakSet();
     let arg={};
     weakList.add(arg);
     //weakList.add(2);不能是数值
     console.log('weakList',weakList);
 }
 //Map,遍历和set一样
 {
     let map= new Map();
     let arr=['123'];
     map.set(arr,456);//添加元素（key,value）
     console.log('map',map,map.get(arr));//get(key)获取值
 }
 {
     let map= new Map([['a',123],['b',456]])
     console.log(map,map.size)
     console.log(map.delete('a'),map)
     console.log(map.clear(),map)
 }
 //同WeakSet
 {
     let weakmap=new WeakMap();
 }