原始的DOM1事件处理机制，是不能绑定多个处理函数。如一个元素在onclick事件先绑定一个函数，用来alert其id，然后再在相同的事件绑定另一个函数，用来alert其style。对不起，第二个函数会覆盖掉第一个，只会alert其style。于是.addEventListener() 与 .attachEvent()被分别开发出来了。为了屏蔽各浏览器的差异，javascript界举办了一个慈善邀请赛，鼓励大家提交各自addEvent/removeEvent 方案，最后由John Resig大神获得。
function addEvent( obj, type, fn ) {
if ( obj.attachEvent ) {
obj["e"+type+fn] = fn;
obj[type+fn] = function(){obj["e"+type+fn]( window.event );}
obj.attachEvent("on"+type, obj[type+fn] );
} else
obj.addEventListener( type, fn, false );
}
function removeEvent( obj, type, fn ) {
if ( obj.detachEvent ) {
obj.detachEvent("on"+type, obj[type+fn] );
obj[type+fn] = null;
} else
obj.removeEventListener( type, fn, false );
}
但是最近我在同一个元素绑定多个onclick事件时，发现些问题。
IE8与其他标准浏览器会弹出1,2,3,4，换言之，先进先出。IE6非先进先出，也不是后进先出，而是2,4,3,1。但如果我们绑定更多函数，IE8的执行顺序就有问题了，IE6与IE7更不用说。谁有好的解决方法吗？
/**
* addEvent & removeEvent -- cross-browser event handling
* Copyright (C) 2006-2007 Dao Gottwald
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Contact information:
* Dao Gottwald <dao at design-noir.de>
*
* @version 1.2.1
*/
function addEvent(o, type, fn) {
o.addEventListener(type, fn, false);
}
function removeEvent(o, type, fn) {
o.removeEventListener(type, fn, false);
}
/*@cc_on if (!window.addEventListener) {
var addEvent = function (o, type, fn) {
if (!o._events) o._events = {};
var queue = o._events[type];
if (!queue) {
o._events[type] = [fn];
if (!o._events._callback)
o._events._callback = function (e) { Event._callListeners(e, o) };
o.attachEvent("on" + type, o._events._callback);
} else if (Event._fnIndex(o, type, fn) == -1)
queue.push(fn);
else return;
Event._mem.push([o, type, fn]);
};
var removeEvent = function (o, type, fn) {
var i = Event._fnIndex(o, type, fn);
if (i < 0) return;
var queue = o._events[type];
if (queue.calling) {
delete queue[i];
if (queue.removeListeners)
queue.removeListeners.push(i);
else
queue.removeListeners = [i];
} else
if (queue.length == 1)
Event._detach(o, type);
else
queue.splice(i, 1);
};
var Event = {
AT_TARGET: 2,
BUBBLING_PHASE: 3,
stopPropagation: function () { this.cancelBubble = true },
preventDefault: function () { this.returnValue = false },
_mem: [],
_callListeners: function (e, o) {
e.stopPropagation = this.stopPropagation;
e.preventDefault = this.preventDefault;
e.currentTarget = o;
e.target = e.srcElement;
e.eventPhase = e.currentTarget == e.target ? this.AT_TARGET : this.BUBBLING_PHASE;
switch (e.type) {
case "mouseover":
e.relatedTarget = e.fromElement;
break;
case "mouseout":
e.relatedTarget = e.toElement;
}
var queue = o._events[e.type];
queue.calling = true;
for (var i = 0, l = queue.length; i < l; i++)
if (queue[i])
if ("handleEvent" in queue[i])
queue[i].handleEvent(e);
else
queue[i].call(o,e);
queue.calling = null;
if (!queue.removeListeners)
return;
if (queue.length == queue.removeListeners.length) {
this._detach(o, e.type);
return;
}
queue.removeListeners = queue.removeListeners.sort(function(a,b){return a-b});
var i = queue.removeListeners.length;
while (i--)
queue.splice(queue.removeListeners[i], 1);
if (queue.length == 0)
this._detach(o, e.type);
else
queue.removeListeners = null;
},
_detach: function (o, type) {
o.detachEvent("on" + type, o._events._callback);
delete o._events[type];
},
_fnIndex: function (o, type, fn) {
var queue = o._events[type];
if (queue)
for (var i = 0, l = queue.length; i < l; i++)
if (queue[i] == fn)
return i;
return -1;
},
_cleanup: function () {
for (var m, i = 0; m = Event._mem[i]; i++)
if (m[1] != "unload" || m[2] == Event._cleanup)
removeEvent(m[0], m[1], m[2]);
}
};
addEvent(window, "unload", Event._cleanup);
} @*/
后来，又发现Dean Edwards也修正了IE事件顺序错乱问题
// addEvent/removeEvent written by Dean Edwards, 2005
// with input from Tino Zijdel
// http://dean.edwards.name/weblog/2005/10/add-event/
function addEvent(element, type, handler) {
if (!handler.$$guid) handler.$$guid = addEvent.guid++;
if (!element.events) element.events = {};
var handlers = element.events[type];
if (!handlers) {
handlers = element.events[type] = {};
if (element["on" + type]) {
handlers[0] = element["on" + type];
}
}
handlers[handler.$$guid] = handler;
element["on" + type] = handleEvent;
};
addEvent.guid = 1;
function removeEvent(element, type, handler) {
if (element.events && element.events[type]) {
delete element.events[type][handler.$$guid];
}
};
function handleEvent(event) {
var returnValue = true;
event = event || fixEvent(window.event);
var handlers = this.events[event.type];
for (var i in handlers) {
this.$$handleEvent = handlers[i];
if (this.$$handleEvent(event) === false) {
returnValue = false;
}
}
return returnValue;
};
function fixEvent(event) {
event.preventDefault = fixEvent.preventDefault;
event.stopPropagation = fixEvent.stopPropagation;
return event;
};
fixEvent.preventDefault = function() {
this.returnValue = false;
};
fixEvent.stopPropagation = function() {
this.cancelBubble = true;
};
function addEvent(element, type, handler) {
if (!handler.$$guid) handler.$$guid = addEvent.guid++;
if (!element.events) element.events = {};//一个巨大的哈希，
var handlers = element.events[type];
if (!handlers) {
handlers = element.events[type] = {};//哈希的每一个键都是哈希
if (element["on" + type]) {
handlers[0] = element["on" + type];
}
}
handlers[handler.$$guid] = handler;
element["on" + type] = function(event) {
var returnValue = true;
event = event || window.event;
var handlers = this.events[event.type];
for (var i in handlers) {
this.$$handleEvent = handlers[i];
if (this.$$handleEvent(event) === false) {
returnValue = false;
}
}
return returnValue;
};
};
addEvent.guid = 1;