javascript whenReady

var whenReady=(function(){
    var funcs=[];
    var ready=false;
    function handler(e){
        if (ready) {
            return;
        }
        if (e.type==="readystatechange" && document.readyState!=="complete") {
            return;
        }
        for(var i=0;i<funcs.length;i++){
            funcs[i].call(document);
        }
        ready=true;
        funcs=null;
    }
    if (document.addEventListener) {
        document.addEventListener("DOMContentLoaded",handler,false);
        document.addEventListener("readystatechange",handler,false);
        window.addEventListener("load", handler, false)
    }else if(document.attachEvent){
        document.attachEvent("onreadystatechange",handler);
        window.attachEvent("onload",handler);
    }
    return function whenReady(f){
        if (ready) {
            f.call(document);
        }else{
            funcs.push(f);
        }
    }
}())