removeClass,addClass,getByClass

function addClass(obj, sClass){
    var re=new RegExp(‘\\b‘+sClass+‘\\b‘);
    
    if(obj.className.search(re)==-1){
        if(obj.className)
        {
            obj.className+=‘ ‘+sClass;
        }else{
            obj.className=sClass;
        }
    }
}

function removeClass(obj, sClass){
    var re=new RegExp(‘\\b‘+sClass+‘\\b‘, ‘g‘);
    
    obj.className=obj.className.replace(re, ‘‘).replace(/^\s+|\s+$/g, ‘‘).split(/\s+/).join(‘ ‘);
    
    if(!obj.className){
        obj.removeAttribute(‘class‘);
    }
}

function getByClass(oParent, sClass){
    if(oParent.getElementsByClassName){
        return oParent.getElementsByClassName(sClass);
    }else{
        var aEle=oParent.getElementsByTagName(‘*‘);
        var re=new RegExp(‘\\b‘+sClass+‘\\b‘);
        var result=[];
        
        for(var i=0;i<aEle.length;i++){
            if(aEle[i].className.search(re)!=-1){
                result.push(aEle[i]);
            }
        }
        return result;
    }
}