我最近在做一个项目的时候，需要写一个javascript的类来对一个ActiveX控件进行封装。而ActiveX控件有它自己的事件以及事件参数，我先后用了“attachEvent”和“$addHandler”来订阅事件，但都有不同的问题，“attachEvent”订阅的事件能正常得到参数，但“this”不再是当前类的实例。而用“$addHandler”订阅的事件能“this”能正确的返回当前类的实例，但ActiveX控件传过来的参数丢失了，而只有一个“Sys.UI.DomEvent”实例的参数。
为了满足需求我就把“$addHandler”方法做了如下的修改，让其能实现“this”和ActiveX控件的事件参数都能正确的得到，并且也保留了“Sys.UI.DomEvent”这个实例的参数。
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var $addHandler = Sys.UI.DomEvent.addHandler = function Sys$UI$DomEvent$addHandler(element, eventName, handler) {
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/// <summary locid="M:J#Sys.UI.DomEvent.addHandler" />
4 /// <param name="element"></param>
5 /// <param name="eventName" type="String"></param>
6 /// <param name="handler" type="Function"></param>
7 // var e = Function._validateParams(arguments, [
8 // { name: "element" },
9 // { name: "eventName", type: String },
10 // { name: "handler", type: Function }
11 // ]);
12 // if (e) throw e;
13 // Sys.UI.DomEvent._ensureDomNode(element);
14 if (eventName === "error") throw Error.invalidOperation(Sys.Res.addHandlerCantBeUsedForError);
15
if (!element._events) {
16 element._events = {};
17
}
18 var eventCache = element._events[eventName];
19 if (!eventCache) {
20 element._events[eventName] = eventCache = [];
21 }
22 var browserHandler;
23 if (element.addEventListener) {
24 browserHandler = function(e) {
25 var ev = null;
26 try {
27 ev = new Sys.UI.DomEvent(e);
28 } catch (ex) { }
29 var al = "handler.call(element, ev";
30 for (var i = 0; i < arguments.length; i++) {
31 al += ", arguments[" + i + "]";
32 }
33 al += ")";
34 return eval(al);
35 //return handler.call(element, ev, arguments);
36 }
37 element.addEventListener(eventName, browserHandler, false);
38 }
39 else if (element.attachEvent) {
40 browserHandler = function() {
41 var e = {};
42 try { e = Sys.UI.DomElement._getWindow(element).event } catch (ex) { }
43 var ev = null;
44 try {
45 ev = new Sys.UI.DomEvent(e);
46 } catch (ex) { }
47 var al = "handler.call(element, ev";
48 for (var i = 0; i < arguments.length; i++) {
49 al += ", arguments[" + i + "]";
50 }
51 al += ")";
52 return eval(al);
53 //return handler.call(element, ev, arguments);
54 }
55 element.attachEvent('on' + eventName, browserHandler);
56 }
57 eventCache[eventCache.length] = { handler: handler, browserHandler: browserHandler };
58
}
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var $addHandler = Sys.UI.DomEvent.addHandler = function Sys$UI$DomEvent$addHandler(element, eventName, handler) {
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/// <summary locid="M:J#Sys.UI.DomEvent.addHandler" />4
/// <param name="element"></param>5
/// <param name="eventName" type="String"></param>6
/// <param name="handler" type="Function"></param>7
// var e = Function._validateParams(arguments, [8
// { name: "element" },9
// { name: "eventName", type: String },10
// { name: "handler", type: Function }11
// ]);12
// if (e) throw e;13
// Sys.UI.DomEvent._ensureDomNode(element);14
if (eventName === "error") throw Error.invalidOperation(Sys.Res.addHandlerCantBeUsedForError);15
if (!element._events) {
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element._events = {};17
}18
var eventCache = element._events[eventName];19
if (!eventCache) {20
element._events[eventName] = eventCache = [];21
}22
var browserHandler;23
if (element.addEventListener) {24
browserHandler = function(e) {25
var ev = null;26
try {27
ev = new Sys.UI.DomEvent(e);28
} catch (ex) { }29
var al = "handler.call(element, ev";30
for (var i = 0; i < arguments.length; i++) {31
al += ", arguments[" + i + "]";32
}33
al += ")";34
return eval(al);35
//return handler.call(element, ev, arguments);36
}37
element.addEventListener(eventName, browserHandler, false);38
}39
else if (element.attachEvent) {40
browserHandler = function() {41
var e = {};42
try { e = Sys.UI.DomElement._getWindow(element).event } catch (ex) { }43
var ev = null;44
try {45
ev = new Sys.UI.DomEvent(e);46
} catch (ex) { }47
var al = "handler.call(element, ev";48
for (var i = 0; i < arguments.length; i++) {49
al += ", arguments[" + i + "]";50
}51
al += ")";52
return eval(al);53
//return handler.call(element, ev, arguments);54
}55
element.attachEvent('on' + eventName, browserHandler);56
}57
eventCache[eventCache.length] = { handler: handler, browserHandler: browserHandler };58
}
