DOMUtils.js

    function $tag(tag, n){return document.getElementsByTagName(tag)[n]}  
    function $id(id){return document.getElementById(id)}
    function $cl(cl, n){return document.getElementsByClassName(cl)[n]}  
    function hasClass(className, targetClass){
        return (className).match(new RegExp(new RegExp('.*(\\b' + targetClass + '\\b).*')))
    }