1 <script>
 2    var arr=[3,4,5,6];
 3    /*in 遍历下标*/
 4    for(var x in arr){
 5         console.log(x)
 6    }
 7    /*for遍历数组元素*/
 8    for(var y of arr){
 9        console.log(y)
10    }
11    /*遍历map*/
12     var map=new Map([["Tom",3],["jack",5],["join",8]]);
13     for(let z of map){
14         console.log(z)
15     }
16     /*遍历set*/
17     var set =new Set([4,5,6,7]);
18     for(let m of set){
19         console.log(m)
20     }
21 
22 </script>