判断添加删除元素的class

window.onload = function() {
    function hasClass(element, className) {
        return !! element.className.match(new RegExp('(\\s|^)' + clssName + '(\\s|$)'));
    }
    function addClass(element, className) {
        if (!hasClass(element, className)) {
            element.className += " " + className;
        }
    }
    function removeClass(element, className) {
        if (hasClass(element, className)) {
            element.className = element.className.replace(new RegExp('(\\s|^)' + clssName + '(\\s|$)'), '');
        }
    }
}