es6 - Promise

promise - 反复进行回调函数.

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 
 4 <head>
 5     <meta charset="UTF-8">
 6     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 7     <meta http-equiv="X-UA-Compatible" content="ie=edge">
 8     <title>Promise</title>
 9 </head>
10 
11 <body>
12     <script>
13         // ES5
14         function async(a, b, c) {
15             setTimeout(function() {
16                 c(a + b);
17             }, 200);
18         }
19 
20         // 反复回调 ... 再次
21         async(1, 2, function(result) {
22             console.log(result);
23             if (result > 2) {
24                 async(2, result, function(result) {
25                     console.log(result);
26                     if (result > 4) {
27                         async(2, result, function(result) {
28                             console.log('result');
29                         });
30                     }
31                 });
32             }
33 
34         });
35         console.log(2);
36 
37 
38         // ####################################################################################################
39 
40 
41         // ES6 - promise
42         function asyncPromise(a, b) {
43             return new Promise(function(resolve, reject) {
44                 setTimeout(function() {
45                     // 如果值不为number对象
46                     if (typeof a !== 'number' || typeof b !== 'number') {
47                         reject(new Error('no number'));
48                     }
49                     resolve(a + b);
50                 }, 200);
51             });
52         }
53         // 错误捕获 - 一旦开始捕获了,catch就不会再重新捕获
54         asyncPromise('a', 2)
55             .then(function(result) {
56                 if (result > 2) {
57                     return asyncPromise(result, 2);
58                 }
59             }, function(err) {
60                 console.log('one no number!');
61             })
62             .then(function(result) {
63                 if (result > 4) {
64                     console.log('result');
65                 }
66             }).catch(function(err) {
67                 console.log(err);
68             });
69     </script>
70 </body>
71 
72 </html>