谁能解释下这段JS代码功能？

问题:

//这段JS功能？
(function () {
    var ie = !!(window.attachEvent && !window.opera);
    var wk = /webkit\/(\d+)/i.test(navigator.userAgent) && (RegExp.$1 < 525);
    var fn = [];
    var run = function () {
        for (var i = 0; i < fn.length; i++) fn[i]();
    };
    var d = document;
    d.ready = function (f) {
        if (!ie && !wk && d.addEventListener) {
            return d.addEventListener('DOMContentLoaded', f, false);
        }
        if (fn.push(f) > 1) return;
        if (ie) {
            (function () {
                try {
                    d.documentElement.doScroll('left');
                    run();
                }
                catch (err) {
                    setTimeout(arguments.callee, 0);
                }
            })();
        } else if (wk) {
            var t = setInterval(function () {
                if (/^(loaded|complete)$/.test(d.readyState))
                    clearInterval(t), run();
            }, 0);
        }
    };
})();

回答1:

文档加载成功事件的实现代码

回答2:

ready方法的兼容性封装