javascript 跨浏览器的事件系统

在ie7发布之前，Dean的addEvent/removeEvent可以称的上是完美了。IE7发布后，引入新的内存泄漏(这个我不是很确定，忘各位前辈们指教。)，决心实现一套相对完美的事件系统。

1、正确的this指向。
2、统一了不同浏览器的事件源调用方式。

/**
 * @fileoverview javascript事件系统
 * @author wangxiang | [email]wxnet2013@gmail.com[/email]
 */
var elements = {};
var eventFns = {};
function addEvent(ele, evt, fn) {
 if (ele.addEventListener) {
  addEvent = function(ele, evt, fn) {
   ele.addEventListener(evt, fn, false);
  };
 } else {
  addEvent = function(ele, evt, fn) {
   var uid = "";
   var eleid = ele.evtid;
   var list = [];
   if (!eleid) {
    uid = 'element_uid_' + Math.floor(Math.random() * 2147483648).toString(36);
    ele.evtid = uid;
    elements[uid] = ele;
    eventFns[uid] = eventFns[uid] || {};
    eventFns[uid]["" + evt] = [];

    // 将之前注册过的事件，添加到事件系统中
    if (ele["on" + evt]) {
     eventFns[uid]["" + evt][0] = ele["on" + evt];
    }

    eventFns[uid]["" + evt].push(fn);
    ele["on" + evt] = function(event) {
     list = eventFns[uid]["" + evt];
     event = event || fixEvent(((this.ownerDocument || this.document || this).parentWindow || window).event);
     for (var i = 0, len = list.length; i < len; i++) {
      list[i].call(this, event);
     }
    };
   } else {
    //其它事件
    if (!eventFns[eleid]["" + evt]) {
     list = eventFns[eleid]["" + evt] = [];
     // 将之前注册过的事件，添加到事件系统中
     if (ele["on" + evt]) {
      eventFns[eleid]["" + evt][0] = ele["on" + evt];
     }
     ele["on" + evt] = function(event) {
      event = event || fixEvent(((this.ownerDocument || this.document || this).parentWindow || window).event);
      for (var i = 0, len = list.length; i < len; i++) {
       list[i].call(this, event);
      }
     };
    }
    eventFns[eleid]["" + evt].push(fn);
   }
  }
 }
 return addEvent(ele, evt, fn);
}

function removeEvent(ele, evt, fn) {
 if (ele.removeEventListener) {
  removeEvent = function(ele, evt, fn) {
   ele.removeEventListener(evt, fn, false);
  }
 } else {
  removeEvent = function(ele, evt, fn) {
   var eleid = ele.evtid;
   if (!eleid) return;
   var list = eventFns[eleid]["" + evt];
   for (var i = 0, len = list.length; i < len; i++) {
    if (fn === list[i]) {
     list.splice(i, 1);
    }
   }
  };
 }
 return removeEvent(ele, evt, fn);
}

// fixEvent written by Dean Edwards, 2005
//http://dean.edwards.name/my/events.js
function fixEvent(event) {
 // add W3C standard event methods
 event.preventDefault = fixEvent.preventDefault;
 event.stopPropagation = fixEvent.stopPropagation;

 //73到110行，取自jquery事件系统
 // Fix target property, if necessary
 if (!event.target) {
  event.target = event.srcElement || document; // Fixes #1925 where srcElement might not be defined either
 }

 // check if target is a textnode (safari)
 if (event.target.nodeType === 3) {
  event.target = event.target.parentNode;
 }

 // Add relatedTarget, if necessary
 if (!event.relatedTarget && event.fromElement) {
  event.relatedTarget = event.fromElement === event.target ? event.toElement: event.fromElement;
 }

 // Calculate pageX/Y if missing and clientX/Y available
 if (event.pageX == null && event.clientX != null) {
  var doc = document.documentElement,
  body = document.body;
  event.pageX = event.clientX + (doc && doc.scrollLeft || body && body.scrollLeft || 0) - (doc && doc.clientLeft || body && body.clientLeft || 0);
  event.pageY = event.clientY + (doc && doc.scrollTop || body && body.scrollTop || 0) - (doc && doc.clientTop || body && body.clientTop || 0);
 }

 // Add which for key events
 if (!event.which && ((event.charCode || event.charCode === 0) ? event.charCode: event.keyCode)) {
  event.which = event.charCode || event.keyCode;
 }

 // Add metaKey to non-Mac browsers (use ctrl for PC's and Meta for Macs)
 if (!event.metaKey && event.ctrlKey) {
  event.metaKey = event.ctrlKey;
 }

 /*
 // Add which for click: 1 === left; 2 === middle; 3 === right
 // Note: button is not normalized, so don't use it
 if (!event.which && event.button !== undefined) {
  event.which = (event.button & 1 ? 1: (event.button & 2 ? 3: (event.button & 4 ? 2: 0)));
 }
*/
 return event;
};
fixEvent.preventDefault = function() {
 this.returnValue = false;
};
fixEvent.stopPropagation = function() {
 this.cancelBubble = true;
};

参考了Dean Edwards的addEvent和jquery的fix机制，目前实现了addEvent/removeEvent的基本功能。