html中自定义菜单随着滚动条滑动的代码实现

<script>

            $(function(){

                window.onscroll=function(){

                var top2=$(document).scrollTop();

                //var top1=document.body.scrollTop;

                console.log("top2:"+top2)

                $("#menu").css("position","relative").css("top",top2);

                }

            });

</script>