1 //Set 2 { 3     let list=new Set(); 4     list.add(5);//添加 5     list.add(7); 6     //属性size就是长度 7     console.log('size',list.size);//2 8 } 9 {10     let arr = [1,2,3,4,5];11     let list = new Set(arr);12     console.log(list.size);//513 }14 {15     //去重16     let list = new Set();17     list.add(1);18     list.add(2);19     list.add(1);20     console.log('size',list);//1,2,没有最后的121 22     let arr=[1,2,3,1,2];23     let list2=new Set(arr);24     console.log('unique',list2);//1,2,3,没有后面的1,225 }26 {27     let arr=['add','delete','clear','has'];28     let list=new Set(arr);29     console.log('has',list.has('add'));//查看是否存在30     console.log('delete',list.delete('add'),list);//删除31     console.log('clear',list.clear('add'),list);//清空32 }33 //遍历34 {35     let arr=['add','delete','clear','has'];36     let list=new Set(arr);37 38     for(let key of list.keys()){39         console.log('key',key);40     }41     for(let value of list.values()){42         console.log('keys',value);43     }44     for(let [key,value] of list.entries()){45         console.log('entries',key,value);46     }47     list.forEach(function(item){48         console.log(item)49     })50 }51 //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52 {53     let weakList=new WeakSet();54     let arg={};55     weakList.add(arg);56     //weakList.add(2);不能是数值57     console.log('weakList',weakList);58 }59 //Map,遍历和set一样60 {61     let map= new Map();62     let arr=['123'];63     map.set(arr,456);//添加元素（key,value）64     console.log('map',map,map.get(arr));//get(key)获取值65 }66 {67     let map= new Map([['a',123],['b',456]])68     console.log(map,map.size)69     console.log(map.delete('a'),map)70     console.log(map.clear(),map)71 }72 //同WeakSet73 {74     let weakmap=new WeakMap();75 }