原生javascript操作class-元素查找-元素是否存在-添加class-移除class

//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;
    }