仿造京东、BILIBILI右侧定位导航Jquery效果

<html xmlns="http://www.w3.org/1999/xhtml"><head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>DEMO</title>
<style type="text/css">

body {
    font: 12px/150% Arial,Verdana,"宋体";
    color: #666;
}
.root61 #backpanel-floor .backpanel-inner {
}
#backpanel-floor .backpanel-inner {
    margin-bottom: 90px;
}
.root61 .backpanel .backpanel-inner {
    margin-left: 605px;
}
.backpanel .backpanel-inner {
    position: fixed;
    z-index: 1001;
    margin-left: 457px;
    left: 50%;
    bottom: 0px;
    padding-bottom: 10px;
}
 
#backpanel-floor .floor-fore0 {
    background-position: 0px 0px;
}
#backpanel-floor .floor-fore1 {
    background-position: 0px -55px;
}
#backpanel-floor .floor-fore2 {
    background-position: 0px -110px;
}
#backpanel-floor .floor-fore3 {
    background-position: 0px -165px;
}
#backpanel-floor .floor-fore4 {
    background-position: 0px -220px;
}
#backpanel-floor .floor-fore5 {
    background-position: 0px -275px;
}
#backpanel-floor .floor-fore6 {
    background-position: 0px -330px;
}
#backpanel-floor .floor-fore7 {
    background-position: 0px -385px;
}
.backpanel .bp-item {
    width: 38px;
    height: 38px;
    background: none repeat scroll 0% 0% #CCC;
    margin-top: 5px;
}
#backpanel-floor .bp-item .floor-links {
    border: 1px solid #DEDEDE;
    height: 31px;
}
#backpanel-floor .floor-fore0 {
    background-position: 0px 0px;
}
.backpanel .bp-item a {
    display: block;
    background-image: url('http://misc.360buyimg.com/product/skin/2013/i/backpanel20140708.png');
    background-color: #AAA;
    background-repeat: no-repeat;
    padding: 5px 0px 0px 7px;
    color: #FFF;
    height: 33px;
    line-height: 1000px;
    overflow: hidden;
}
a {
    color: #666;
    text-decoration: none;
}
#backpanel-floor .floor-links:hover, #backpanel-floor .curr a.floor-links, #backpanel-floor .curr .floor-links:hover {
    background-image: none;
    background-color: #FDEEEE;
    color: #ED5759;
    border: 1px solid #ED5759;
    line-height: 13px;
}
#backpanel-floor .bp-item .floor-links {
    border: 1px solid #DEDEDE;
    height: 31px;
}
#backpanel-floor .floor-fore0 {
    background-position: 0px 0px;
}
.backpanel .bp-item a:hover {
    line-height: 14px;
    color: #FFF;
    background-image: none;
}
.bp-item a:hover, .bp-item a:visited {
    text-decoration: none;
}
.backpanel .bp-item a {
    display: block;
    background-image: url('http://misc.360buyimg.com/product/skin/2013/i/backpanel20140708.png');
    background-color: #AAA;
    background-repeat: no-repeat;
    padding: 5px 0px 0px 7px;
    color: #FFF;
    height: 33px;
    line-height: 1000px;
    overflow: hidden;
}
a:hover {
    color: #E4393C;
    text-decoration: underline;
}
:focus {
    outline: 0px none;
}
a {
    color: #666;
    text-decoration: none;
}

</style>
<script src="http://code.jquery.com/jquery-1.8.0.min.js"></script>
<script>

var step = 153; // 表示每一层153px
$(function(){
    $(document).scroll(function(){
        var top = $(document).scrollTop();
        if(top > 0){
            $("#backpanel-floor").fadeIn(200);
        } else {
            $("#backpanel-floor").fadeOut(200);
        }
        var idx = parseInt(top/step);
 
        $(".backpanel-inner .bp-item").eq(idx).addClass("curr").siblings().removeClass("curr");
    });
 
    $(".backpanel-inner .bp-item").click(function(){
        var idx = $(this).index();
        $(this).addClass("curr").siblings().removeClass("curr");
        $(document).scrollTop(idx*step+1);
    });
});

</script>
 
</head>
  
 <body style="height:2000px" class="root61"> 
  <div style="display: none;" id="backpanel-floor" class="w backpanel hide">
   <div class="backpanel-inner">
    <div class=" bp-item bp-item-floor-links floor-fore0" data-top="0"> 
     <a href="#none" class="floor-links floor-fore0 curr" target="_self">家电通讯</a>
     <s></s>
    </div>
    <div class=" bp-item bp-item-floor-links floor-fore1" data-top="0"> 
     <a href="#none" class="floor-links floor-fore1" target="_self">电脑数码</a>
     <s></s>
    </div>
    <div class=" bp-item bp-item-floor-links floor-fore2" data-top="0"> 
     <a href="#none" class="floor-links floor-fore2 curr" target="_self">服饰鞋包</a>
     <s></s>
    </div>
    <div class=" bp-item bp-item-floor-links floor-fore3" data-top="0"> 
     <a href="#none" class="floor-links floor-fore3" target="_self">美容珠宝</a>
     <s></s>
    </div>
    <div class=" bp-item bp-item-floor-links floor-fore4" data-top="0"> 
     <a href="#none" class="floor-links floor-fore4" target="_self">居家生活</a>
     <s></s>
    </div>
    <div class=" bp-item bp-item-floor-links floor-fore5" data-top="0"> 
     <a href="#none" class="floor-links floor-fore5" target="_self">母婴玩具</a>
     <s></s>
    </div>
    <div class=" bp-item bp-item-floor-links floor-fore6" data-top="0"> 
     <a href="#none" class="floor-links floor-fore6" target="_self">食品保健</a>
     <s></s>
    </div>
    <div class=" bp-item bp-item-floor-links floor-fore7" data-top="0"> 
     <a href="#none" class="floor-links floor-fore7" target="_self">图书音像</a>
     <s></s>
    </div>
   </div>
  </div> 
 </body>
 
</html>