事件兼容及对内存的影响

 1 var EventUtil={
 2        addHandler:function(element,type,handler){    //为元素添加事件处理程序
 3            if(typeof element.addEventListener=="function"){
 4                element.addEventListener(type,handler,false);   //DOM2
 5            }else if(typeof element.attachEvent=="function"){
 6                element.attachEvent("on"+type,handler);   //IE
 7            }else{
 8               element["on"+type]=handler;    //所有的浏览器都支持
 9            }
10        },
11 
12        getEvent:function(event){    //获取包含事件信息的event对象
13            return event?event:window.event;
14        },
15 
16        getTarget:function(event){       //获取事件的目标target
17            return event.target||event.srcElement;
18        },
19        getRelatedTarget:function(event){   //获取相关元素,针对mouseover与mouseout事件
20            if(event.relatedTarget){
21                return event.relatedTarget;
22            }else if(event.fromElement){
23                return event.fromElement;
24            }else if(event.toElement){
25                return event.toElement;
26            }else{
27                return null;
28            }
29        },    
30        getButton:function(event){    //获取鼠标的按钮，针对mousedown和mouseup事件
31            if(document.implementation.hasFeature("MouseEvents","2.0")){
32                return event.button;
33            }else{
34                switch(event.button){
35                    case 0:
36                    case 1:
37                    case 3:
38                    case 5:
39                    case 7:
40                        return 0; //主鼠标
41                    case 4:
42                        return 1; //中间鼠标
43                    case 2:
44                    case 6:
45                         return 2;  //次鼠标
46                }
47            }
48        },
49         getWheelDelta:function(event){  //鼠标滚动事件
50            if(event.wheelDelta){
51                return event.wheelDelta;
52            }else{
53                return -40*event.detail;
54            }
55        },
56        getCharCode:function(event){   //获取字符编码,针对keypress事件
57            if(typeof event.charCode=="Number"){
58                return event.charCode;
59            }else{
60                return event.keyCode;
61            }
62        },
63        preventDefault:function(event){  //阻止事件的默认行为
64            if(event.preventDefault){
65                event.preventDefault();
66            }else{
67                event.returnValue=false;
68            }
69        },
70        stopPropagation:function(event){  //阻止事件流
71            if(event.stopPropagation){
72                event.stopPropagation();
73            }else{
74                event.cancelBubble=true;
75            }
76        },
77        removeHandler:function(element,type,handler){  //删除事件
78            if(typeof element.removeEventListener=="function"){
79                element.removeEventListener(type,handler,false);
80            }else if(typeof element.detachEvent=="function"){
81                element.detachElement("on"+type,handler);
82            }else{
83                element["on"+type]=null;
84            }
85        }
86    };