JS_常用方法_dowhileExist , addLoadEvent

var dowhileExist = function(objID,fn){
var obj = document.getElementById(objID);
(obj&&fn) && fn(obj);
}

function addLoadEvent(func){
var oldonload = window.onload;
if(typeof window.onload != 'function'){
window.onload = func;
}
else {
window.onload = function(){
oldonload();
func();
}
}
}