html 自定义菜单随着滚动条滑动

1.给一个div

	<style>
			#menu{
				position: relative;top: 0px;
			}
	</style>
<div id="menu"> </div>

2.事件菜单，点击

<script>
		function showHide(num){
			if(num==1){
				$('html, body').animate({scrollTop: $('#biaoji1').offset().top},"slow")//"slow"
			}else if(num==2){
				$('html, body').animate({scrollTop: $('#biaoji2').offset().top},"slow")
			}else if(num==3){
				$('html, body').animate({scrollTop: $('#biaoji3').offset().top},"slow")
			}
		}
	</script>

3.滚动鼠标

<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>