京东楼层切换

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
img{
display: block;
}
#menu{
32px;height:360px;
position:fixed;
top:200px;left:0px;
}
#menu ul li{
32px;height:32px;
list-style-type:none;
color:#8F8583;
text-align:center;
line-height: 32px;
border-bottom:1px dotted #ddd;
position:relative;
}
#menu ul li span{
display:block;32px;height:32px;
background:#C81623;
position:absolute;
top:0;left:0;
color:#fff;font-size:12px;
display: none;
}
#menu ul li:hover span{display:block; }
#menu ul li span.active{color:#C81623;background:#fff;display:block;}
#content{
1220px;
margin:0 auto;
}
#footer{1220px;height:600px;background:#FE7678;}
.container{margin:0 auto;}
</style>
</head>
<body>
<div id="menu">
<ul>
<li>1F<span>服饰</span></li>
<li>2F<span>美妆</span></li>
<li>3F<span>手机</span></li>
<li>4F<span>家电</span></li>
<li>5F<span>数码</span></li>
<li>6F<span>运动</span></li>
<li>7F<span>居家</span></li>
<li>8F<span>母婴</span></li>
<li>9F<span>食品</span></li>
<li>10F<span>图书</span></li>
<li>11F<span>服务</span></li>
</ul>
</div>


<div id="content">
<div class="louti" id="louti1"><img src="img/1.jpg" alt=""></div>
<div class="louti" id="louti2"><img src="img/2.jpg" alt=""></div>
<div class="louti" id="louti3"><img src="img/3.jpg" alt=""></div>
<div class="louti" id="louti4"><img src="img/1.jpg" alt=""></div>
<div class="louti" id="louti5"><img src="img/1.jpg" alt=""></div>
<div class="louti" id="louti6"><img src="img/1.jpg" alt=""></div>
<div class="louti" id="louti7"><img src="img/1.jpg" alt=""></div>
<div class="louti" id="louti8"><img src="img/1.jpg" alt=""></div>
<div class="louti" id="louti9"><img src="img/1.jpg" alt=""></div>
<div class="louti" id="louti10"><img src="img/1.jpg" alt=""></div>
<div class="louti" id="louti11"><img src="img/1.jpg" alt=""></div>
</div>


<div id="footer" class="container"></div>
<script src="js/jquery-1.11.3.js"></script>
<script type="text/javascript">
$(function(){
var _index=0;
$("#menu ul li").click(function(){
$(this).find("span").addClass("active").parent().siblings().find("span").removeClass("active");
_index=$(this).index()+1;
//通过拼接字符串获取元素，再取得相对于文档的高度
var _top=$("#louti"+_index).offset().top;
//scrollTop滚动到对应高度
$("body,html").animate({scrollTop:_top},500);
});
var nav=$("#menu"); //得到导航对象
var win=$(window); //得到窗口对象
var sc=$(document);//得到document文档对象。
win.scroll(function(){
//获取滚动元素对应的索引!!!重难点
var height = $(".louti").height();
var index=Math.floor(sc.scrollTop()/height);
$("#menu ul li span").eq(index).addClass("active").parent().siblings().find("span").removeClass("active");

});
});
</script>
</body>
</html>