//判断元素是否有class function hasClass(ele, cls) {         return ele.className.match(new RegExp('(\\s|^)'+cls+'(\\s|$)'));    } //元素增加class    function addClass(ele, cls) {         if (!hasClass(ele, cls)) ele.className += " "+cls;    } //元素移除class    function removeClass(ele, cls) {        if (hasClass(ele, cls)) {            var reg = new RegExp('(\\s|^)'+cls+'(\\s|$)');            ele.className = ele.className.replace(reg, ' ');        }    }    /* className, rootId(限制范围id名), tagName(标签名称)*/    function getElementsByClassName(cls, rid, tag) {        root = rid && document.getElementById(rid) || document;        if (root.getElementsByClassName) {            return root.getElementsByClassName(cls);        }        tag = tag || '*';        var elems = root.getElementsByTagName(tag);        var ret = [];        for (var i = 0, len = elems.length; i < len; i++) {            var elem = elems[i];            if ((' ' + elem.className + ' ').indexOf(' ' + cls + ' ') > -1) {                ret.push(elem);            }        }        return ret;    }