Array.prototype.map方法 

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 3  * @Date: 2021-11-03 22:06:54
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 9 
10 <!DOCTYPE html>
11 <html lang="en">
12 <head>
13     <meta charset="UTF-8">
14     <meta http-equiv="X-UA-Compatible" content="IE=edge">
15     <meta name="viewport" content="width=device-width, initial-scale=1.0">
16     <title>Document</title>
17 </head>
18 <body>
19     <script>
20         // map函数的直接使用
21         var arr = [1,2,3,4]
22         var array = arr.map((item,index) => {
23             return item * 2;
24         })
25         console.log(array);
26 
27         
28         // 写一个新的newMap函数
29         function newMap (arr,mapCallback) {
30             //检查参数是否正确
31             if (!Array.isArray(arr) || !arr.length || typeof mapCallback !== 'function'){
32                 return []
33             }else{
34                 let result = []
35                 for (let i = 0,len = arr.length;i < len;i++){
36                     result.push(mapCallback(arr[i],i,arr))
37                 } 
38                 return result
39             }
40         }
41         var res = newMap(arr,(item) => {
42             return item * 2
43         })
44         console.log(res);
45 
46     </script>
47 </body>
48 </html>

 

posted @ 2021-11-03 22:22  TM_cc  阅读(64)  评论(0)    收藏  举报