自定义事件

 1 //自定义事件
 2  function EventTarget() {
 3      this.handlers = {};
 4  }
 5  EventTarget.prototype = {
 6      constructor: EventTarget,
 7      //注册
 8      addHandler: function(type, handler) {
 9          if (typeof this.handlers[type] == "undefined") {
10              this.handlers[type] = [];
11          }
12          this.handlers[type].push(handler);
13      },
14      //触发
15      fire: function(event) {
16          if (!event.target) {
17              event.target = this;
18          }
19          if (this.handlers[event.type] instanceof Array) {
20              var handlers = this.handlers[event.type];
21              for (var i = 0, len = handlers.length; i < len; i++) {
22                  handlers[i](event);
23              }
24          }
25      },
26      //注销
27      removeHandler: function(type, handler) {
28          if (this.handlers[type] instanceof Array) {
29              var handlers = this.handlers[type];
30              for (var i = 0, len = handlers.length; i < len; i++) {
31                  if (handlers[i] === handler) {
32                      break;
33                  }
34              }
35              handlers.splice(i, 1);
36          }
37      }
38  };

 1 //使用方法
 2  function handleMessage(event) {
 3      alert("Message received: " + event.message);
 4  }
 5  //创建一个新对象
 6  var target = new EventTarget();
 7  //添加一个事件处理程序
 8  target.addHandler("message", handleMessage);
 9  //触发事件
10  target.fire({
11      type: "message",
12      message: "Hello world!"
13  });
14  //删除事件处理程序
15  target.removeHandler("message", handleMessage);
16  //再次，应没有处理程序
17  target.fire({
18      type: "message",
19      message: "Hello world!"
20  });