map &forEach 

var array1 = [1,4,9,16];
const map1 = array1.map(x => x *2);
console.log(map1);
打印结果为：

Array [2,8,18,32]
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<body>

<button onclick="numbers.forEach(myFunction)">点我</button>

<p>计算后的值: <span id="demo"></span></p>

<script>
var numbers = [1, 2,3, 4];

function myFunction(item,index,arr) {
    console.log(arr);
    arr[index] = item*2;
    demo.innerHTML = numbers;
}
</script>

</body>
</html>

 

posted @ 2020-03-02 17:30  Jinsuo  阅读(90)  评论(0)  编辑  收藏  举报