dojo/Deferred类和dojo/promise类的使用

前端开发作者： 2024-08-25 15:00:01

参考博客：https://blog.csdn.net/blog_szhao/article/details/50220181 　　　 https://dojotoolkit.org/documentation/tutorials/1.10/promises/ Deferred是一个绝妙又给力的东西，但是它其实是更棒的promis的实现，dojo/Deferred 模块是promise在

可以为三个状态中的一个：unfulfilled、resolved、 rejected
可以从unfulfilled转变到resolved或者rejected
实现了一个 then 方法来针对状态改变的通知注册回调
回调不能改变promise产生的值
promise的 then 方法返回一个新的promise，在保持原promise的值不变的情况下提供链式操作

 1 <!DOCTYPE HTML>
 2 <html lang="en">
 3 <head>
 4     <meta charset="utf-8">
 5     <title>Demo: dojo/Deferred</title>
 6     <link rel="stylesheet" href="style.css" media="screen">
 7 </head>
 8 <body>
 9 <h1>Demo: dojo/Deferred</h1>
10 <ul id="userlist"></ul>
11 <!-- load dojo and provide config via data attribute -->
12 <script src="//ajax.googleapis.com/ajax/libs/dojo/1.10.4/dojo/dojo.js" data-dojo-config="isDebug: 1,async: 1,parSEOnLoad: 1"></script>
13 <script>
14     require(["dojo/Deferred","dojo/request","dojo/_base/array","dojo/dom-construct","dojo/dom","dojo/domReady!"],15         function(Deferred,request,arrayUtil,domConstruct,dom) {
16             /*var deferred = new Deferred(),17                 userlist = dom.byId("userlist");
18 
19             deferred.then(function(res){
20                 arrayUtil.forEach(res,function(user){
21                     domConstruct.create("li",{
22                         id: user.id,23                         innerHTML: user.username + ": " + user.name
24                     },userlist);
25                 });
26             },function(err){
27                 domConstruct.create("li",{
28                     innerHTML: "Error: " + err
29                 },userlist);
30             });
31 
32             // Send an HTTP request
33             request.get("users.json",{
34                 handleAs: "json"}).then(
35                 function(response){
36                     // Resolve when content is received
37                     deferred.resolve(response);
38                 },39                 function(error){
40                     // Reject on error
41                     deferred.reject(error);
42                 }
43             );*/
44 
45             //由于dojo/Deferred模块是Dojo的promise接口的主要实现，所以上面这个例子可以这样写：
46             var deferred = request.get("users.json",{
47                 handleAs: "json"
48             });
49             deferred.then(function(res){
50                 var userlist = dom.byId("userlist");
51                 arrayUtil.forEach(res,function(user){
52                     domConstruct.create("li",{
53                         id: user.id,54                         innerHTML: user.username + ": " + user.name
55                     },userlist);
56                 });
57             },function(err){
58                 // This shouldn‘t occur,but it‘s defined just in case
59                 alert("An error occurred: " + err);
60             });
61         });
62 </script>
63 </body>
64 </html>