observer pattern in javascript

1 <script type="text/javascript">
2     window.onload=function(){
3         var b=new B();
4
5         var a = new A();
6         a.i = "the 1st object will be show"
7         b.attObj(a);//object a be attach
8
9         var a1 = new A();
10         a1.i = "the 2nd object will be show"
11         b.attObj(a1);//object b be attach
12
13         //invoke method of object b
14         b.m1();
15     }
16     function A(){  //class A be defined
17         this.i=1;
18         var _this=this;
19         this.m1=function(){
20              alert(this.i);
21         }
22     }
23
24     function B(){
25         this.extObj = [];
26         this.attObj = function(obj){
27             this.extObj.push(obj);
28         }
29         this.m1=function(){
30             //when all operation of object B be finished,all <span class="dict18">subscriber will be notify</span>.
31             for(var i=0;i<this.extObj.length;i++){
32                 this.extObj[i].m1();
33             }
34         }
35     }
36
37     </script>