js onmouseout事件,该怎么处理

<ul id="layer_city_001001001" onmouseout="ShowLayer.HideCity(this);"><li class="more"><input type="checkbox" value="001001001001" class="catalogChk"><a href="javascript:void(0);">市辖区</a></li><li class="more"><input type="checkbox" value="001001001002" class="catalogChk"><a href="javascript:void(0);">县</a></li></ul>

            ShowLayer.HideCity = function (city_id) {
                $(city_id).attr("style", $(city_id).attr("style") + ";" + "display:none");
            }