JS實現觀察者模式

觀察者模式 又稱 訂閱發佈模式

QQ Email 客戶端訂閱消息 從報社發佈消息，而後客戶d端接收。

代碼以下：

 1             //觀察者模式  又稱訂閱發佈模式
 2             function Newspaper() {
 3                 var list = new Set();
 4                 //訂閱
 5                 this.subscribe = function(c) {
 6                     list.add(c);
 7                 }
 8                 //取消訂閱
 9                 this.unsubscribe = function(c) {
10                     list.remove();
11                 }
12                 //發佈新聞
13                 this.publish = function(msg) {
14                     for(var i of list.keys()) {
15                         i.notice(msg);
16                     }
17                 }
18                 //每4s產生一條新聞
19                 this.start = function() {
20                     setInterval(function() {
21                         this.publish(Math.random());
22                     }.bind(this), 4000);
23                 }
24             }
25 
26             function Client() {
27                 this.notice = function(msg) {
28                     console.log(this.type + "內容：" + msg);
29                 }
30             }
31             var QQ = function() {
32                 this.type = "QQ";
33             };
34             QQ.prototype = new Client();
35             var Email = function() {
36                 this.type = "Email";
37             };
38             Email.prototype = new Client();
39 
40             var theme = new Newspaper();
41             theme.start();
42             theme.subscribe(new QQ("aaa"));
43             theme.subscribe(new Email("aaa@qq.com"));