mass种子模块之domready

总结：由于IE6/7/8不支持DOMContentLoaded事件，虽然它支持onreadystatechange事件，但是readyState=complete几乎和onload事件一样，需要等页面中的外部资源加载完后才触发，想要尽快可采用doScroll检测法（仅在非iframe下有效）

var turbo = turbo || {};
var W3C = document.addEventListener ? true : false;
var doc = document, html = document.documentElement;
var readyList = [];
turbo.ready = function(fn) {
    //不管是哪个分支，只要触发过一次ready事件readyList就会为null
    if (readyList) {
        readyList.push(fn);
    } else {
        fn();
    }
};
function fireReady() {
    if (readyList && readyList.length) {
        for (var i = 0, len = readyList.length; i < len; i++) {
            var fn = readyList[i];
            fn();
        }
    }
    readyList = null;
}

function doScrollCheck() {
    try {
        html.doScroll('left');
        fireReady();
    } catch (e) {
        setTimeout(doScrollCheck, 50);
    }
}

var ready = W3C ? "DOMContentLoaded" : "readystatechange";
//由于firefox3.6不支持readyState，则在不支持readyState的时需手动赋值给它
if (!doc.readyState) {
    //如果doc.body已存在则说明domcontentloaded了，将doc.readySate设置为complete
    var readyState = doc.readySate = doc.body ? "complete" : "loading";
}

if (doc.readyState == 'complete') {
    fireReady();
} else {
    $.bind(doc, ready, function() {
        if (W3C || doc.readyState == 'complete') {
            fireReady();
            //firefox3.6,我觉得这里设不设置都行，因为这里已经用不到了doc.readyState了
            if (readyState) {
                doc.readyState = 'complete';
            }
        }
    })
    //ie下使用doScroll，尽量提前触发ready，此方法只在非iframe下的页面有效
    var top = false;
    try {
        top = doc.frameElement == null && doc.documentElement;
    } catch (e) {}
    if (top && top.doScroll) {
        doScrollCheck();
    }
}

有点看不懂mass里最后一段调用doScrollCheck的代码，故采用的jQuery的写法.