$(function () {

            //根據對(dui)象得到它所要用(yong)的(de)ＣＳＳ名稱
            var getClass = function (obj) {
                var className;

                switch ($(obj).closest("ul").attr("id")) {
                    case "a1":
                        className = "a1";
                        break;
                    case "a2":
                        className = "a2";
                        break;
                    default:
                        console.log("error type");
                        break;
                }
                return className;
            };

            //滑動(dong)變色操(cao)作
            $("#a1,#a2").find("li").hover(function () {
                $(this).addClass(getClass(this));

            }, function () {
                $(this).removeClass(getClass(this));
            });
        });

 <ul id="a1">
        <li>one</li>
        <li>two</li>
    </ul>
    <ul id="a2">
        <li>1</li>
        <li>2</li>
　</ul>