if while for 都和java一样
方法一
let a=[1,2,3,4,5,6];
for(let value in a){
console.log(a[value])
}
方法二
let a=[1,2,3,4,5,6];
a.forEach(function (value) {
console.log(value);
})
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script>
‘use strict‘;
//es6
let map=new Map([[‘tom‘,99],[‘jack‘,99],[‘jie‘,10]]);
let value=map.get(‘tom‘);
map.set(‘admin‘,12);
console.log(value);
</script>
</head>
<body>
</body>
</html>
无序不重复集合
let set=new Set([1,2,3,4,4,4,4,4]);
console.log(set);
//可以add delete
set.add(8);
set.delete(8);
原文：https://www.cnblogs.com/OfflineBoy/p/14736236.html