用纯原生js实现jquery的ready函数(两种实现)

var dom = new function() {
var dom = [];
dom.isReady = false;
dom.isFunction = function(obj) {
return Object.prototype.toString.call(obj) === "[object Function]";
}

//先会执行下面的分支函数，然后执行dom.initReady()函数，因为要等到DOM建完后才会执行
dom.Ready = function(fn) {
dom.initReady();//如果没有建成DOM树，则走第二步，存储起来一起杀
if(dom.isFunction(fn)) {
if(dom.isReady) {
fn();//如果已经建成DOM，则来一个杀一个
} else {
dom.push(fn);//存储加载事件
}
}
}
dom.fireReady = function() {
if (dom.isReady)  return;
dom.isReady = true;
for(var i=0, n=dom.length; i<n; i++) {
dom[i]();
}
dom.length = 0;//清空事件
}
dom.initReady = function() {
if (document.addEventListener) {
document.addEventListener( "DOMContentLoaded", function() {
document.removeEventListener( "DOMContentLoaded", arguments.callee, false );//清除加载函数
dom.fireReady();
}, false );
} else {
if (document.getElementById) {
document.write("<script id=\"ie-domReady\" defer='defer'src=\"//:\"><\/script>");
document.getElementById("ie-domReady").onreadystatechange = function() {
if (this.readyState === "complete") {
dom.fireReady();
this.onreadystatechange = null;
this.parentNode.removeChild(this)
}
};
}
}
}
return dom;
}

//浏览器检测
(function () {
window.sys = {};
var ua = navigator.userAgent.toLowerCase();
var s;
(s = ua.match(/msie ([\d.]+)/)) ? sys.ie = s[1] :
(s = ua.match(/firefox\/([\d.]+)/)) ? sys.firefox = s[1] :
(s = ua.match(/chrome\/([\d.]+)/)) ? sys.chrome = s[1] :
(s = ua.match(/opera\/.*version\/([\d.]+)/)) ? sys.opera = s[1] :
(s = ua.match(/version\/([\d.]+).*safari/)) ? sys.safari = s[1] : 0;

if (/webkit/.test(ua)) sys.webkit = ua.match(/webkit\/([\d.]+)/)[1];
})();

//DOM加载
function Ready(fn) {
var isReady = false;
var timer = null;
function doReady() {
if (timer) clearInterval(timer);
if (isReady) return;
isReady = true;
fn();
}

if ((sys.opera && sys.opera < 9) || (sys.firefox && sys.firefox < 3) || (sys.webkit && sys.webkit < 525)) {
timer = setInterval(function () {
if (document && document.getElementById && document.getElementsByTagName && document.body) {
doReady();
}
}, 1);
} else if (document.addEventListener) {//W3C
addEvent(document, 'DOMContentLoaded', function () {
fn();
removeEvent(document, 'DOMContentLoaded', arguments.callee);
});
} else if (sys.ie && sys.ie < 9){
var timer = null;
timer = setInterval(function () {
try {
document.documentElement.doScroll('left');
doReady();
} catch (e) {};
}, 1);
}
}

//跨浏览器添加事件绑定
function addEvent(obj, type, fn) {
if (typeof obj.addEventListener != 'undefined') {
obj.addEventListener(type, fn, false);
} else {
//创建一个存放事件的哈希表(散列表)
if (!obj.events) obj.events = {};
//第一次执行时执行
if (!obj.events[type]) {
//创建一个存放事件处理函数的数组
obj.events[type] = [];
//把第一次的事件处理函数先储存到第一个位置上
if (obj['on' + type]) obj.events[type][0] = fn;
} else {
//同一个注册函数进行屏蔽，不添加到计数器中
if (addEvent.equal(obj.events[type], fn)) return false;
}
//从第二次开始我们用事件计数器来存储
obj.events[type][addEvent.ID++] = fn;
//执行事件处理函数
obj['on' + type] = addEvent.exec;
}
}

//为每个事件分配一个计数器
addEvent.ID = 1;

//执行事件处理函数
addEvent.exec = function (event) {
var e = event || addEvent.fixEvent(window.event);
var es = this.events[e.type];
for (var i in es) {
es[i].call(this, e);
}
};

//同一个注册函数进行屏蔽
addEvent.equal = function (es, fn) {
for (var i in es) {
if (es[i] == fn) return true;
}
return false;
}

//把IE常用的Event对象配对到W3C中去
addEvent.fixEvent = function (event) {
event.preventDefault = addEvent.fixEvent.preventDefault;
event.stopPropagation = addEvent.fixEvent.stopPropagation;
event.target = event.srcElement;
return event;
};

//IE阻止默认行为
addEvent.fixEvent.preventDefault = function () {
this.returnValue = false;
};

//IE取消冒泡
addEvent.fixEvent.stopPropagation = function () {
this.cancelBubble = true;
};

//跨浏览器删除事件
function removeEvent(obj, type, fn) {
if (typeof obj.removeEventListener != 'undefined') {
obj.removeEventListener(type, fn, false);
} else {
if (obj.events) {
for (var i in obj.events[type]) {
if (obj.events[type][i] == fn) {
delete obj.events[type][i];
}
}
}
}
}