gistfile1.js

    function hasClass(node, className){
        var classes = node.getAttribute('class');
        if( classes === '' || undefined ){
            return false;
        }else{
            classes = classes.split(/\s/);
            for(var i=0; i < classes.length; i++){
                if(classes[i] === className){
                    return true;
                } 
            }
            return false;
        }
    }
    
    function addClass(node, className){
        var oldClass = node.getAttribute('class');
        if(oldClass === '' || undefined){
            node.setAttribute('class', className);
        }else{
            node.setAttribute('class', oldClass + ' ' + className);
        }
        return true;
    }
    
    function removeClass(node, className){
        var classes = node.getAttribute('class');
        var noClass = function(){
            console.log('Такой класс отсутствует, нечего удалять.');
            return false;
        }
        if( classes === '' || undefined ){
            noClass();
        }else{
            classes = classes.split(/\s/);
            var index = classes.indexOf(className);
            if(index === -1){
                noClass();
            }else{
                classes.splice(index, 1);
                classes = classes.join(' ');
                node.setAttribute('class', classes);
                return true;
            }
        }
    }