Get elements by classname cross browser

gistfile1.js

function byClass(matchClass){
    if (!document.getElementsByClassName){
        var elements = document.getElementsByTagName('*'),
            i=0,
            nodeList = [],
            reg = new RegExp('(^|\\s)' + matchClass + '(\\s|$)')
       
        for (i=0; i < elements.length;i++)
        {
            if(elements[i].className.match(reg) !== null){
                 nodeList.push(elements[i]);
            }
        }
        return nodeList;
    }else{
        return document.getElementsByClassName(matchClass);
    }
}