今天我们来学习jQuery.Event对象。jQuery为了添加自己的处理机制，及可以传递用户自定义数据，于是Event对象就出世了。
1 jQuery.Event = function( src, props ) {
2 //instanceof 用于判断一个变量是否某个对象的实例
3 if ( !(this instanceof jQuery.Event) ) {
4 return new jQuery.Event( src, props );
5 }
6
7 // Event object
8 if ( src && src.type ) {
9 /*
10 如果是event对象
11 * */
12 this.originalEvent = src;//将原生的event对象存于Event中
13 this.type = src.type;//事件类型
14
15 // Events bubbling up the document may have been marked as prevented
16 // by a handler lower down the tree; reflect the correct value.
17 /*
18 修正isDefaultPrevented方法
19 * */
20 this.isDefaultPrevented = src.defaultPrevented ||
21 src.defaultPrevented === undefined &&
22 // Support: IE < 9, Android < 4.0
23 src.returnValue === false ?
24 returnTrue :
25 returnFalse;
26
27 // Event type
28 } else {
29 //如果event是事件名称
30 this.type = src;
31 }
32
33 // Put explicitly provided properties onto the event object
34 //添加自定义属性
35 if ( props ) {
36 jQuery.extend( this, props );
37 }
38
39 // Create a timestamp if incoming event doesn't have one
40 this.timeStamp = src && src.timeStamp || jQuery.now();//添加时间戳
41
42 // Mark it as fixed
43 this[ jQuery.expando ] = true;//标识event已被处理过
44 };
45
46 jQuery.Event.prototype = {
47 isDefaultPrevented: returnFalse,
48 isPropagationStopped: returnFalse,
49 isImmediatePropagationStopped: returnFalse,
50
51 preventDefault: function() {
52 /*
53 修正【阻止默认事件】
54 * */
55 var e = this.originalEvent;//取出原生evnet
56
57 this.isDefaultPrevented = returnTrue;
58 if ( !e ) {
59 return;
60 }
61
62 // If preventDefault exists, run it on the original event
63 if ( e.preventDefault ) {
64 e.preventDefault();
65
66 // Support: IE
67 // Otherwise set the returnValue property of the original event to false
68 } else {
69 e.returnValue = false;
70 }
71 },
72 stopPropagation: function() {
73 /*
74 修正【停止冒泡】
75 * */
76 var e = this.originalEvent;//取出原生evnet
77
78 this.isPropagationStopped = returnTrue;
79 if ( !e ) {
80 return;
81 }
82 // If stopPropagation exists, run it on the original event
83 if ( e.stopPropagation ) {
84 e.stopPropagation();
85 }
86
87 // Support: IE
88 // Set the cancelBubble property of the original event to true
89 e.cancelBubble = true;
90 },
91 stopImmediatePropagation: function() {
92 /*
93 修正【stopImmdiatePropagation】
94 stopImmediatePropagation 的功能比stopPropagation 多一些，
95 除了可以阻止事件冒泡之外，还可以把这个元素绑定的同类型事件也阻止了。
96 * */
97 var e = this.originalEvent;
98
99 this.isImmediatePropagationStopped = returnTrue;
if ( e && e.stopImmediatePropagation ) {
e.stopImmediatePropagation();
}
this.stopPropagation();
}
107 };
Event方法主要是对兼容性做了处理看注释应该就明白了！