jQuery学习-事件之绑定事件（四）

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！