这个函数的定义不太明白，希望大牛指点

        /**

         * Given a set of nodes, it returns them as an array.  Used to find

         * siblings of an element

         * @param {Nodelist} nodes Node list to search

         * @param {Object=} element [optional] objects to find siblings off of

         * @return {Array} array of siblings

         * @api private

         */

         var nundefined;

        function siblings(nodes, element) {

            var elems = [];

            if (nodes == nundefined)

                return elems;



            for (; nodes; nodes = nodes.nextSibling) {

                if (nodes.nodeType === 1 && nodes !== element) {

                    elems.push(nodes);

                }

            }

            return elems;

        }