jquer实现图片切换
 
         
            
 
                
 
                
 
                
 
                
                 
 
        

CSS代码（tupianqiehuan.css）：  

*{margin:0;padding:0;} 
body{font-size:12px;color:#222;font-family:Verdana,Arial,Helvetica,sans-serif;background:#f0f0f0;} 
.clearfix:after{content: ".";display: block;height: 0;clear: both;visibility: hidden;} 
.clearfix{zoom:1;} 
ul,li{list-style:none;} 
img{border:0;} 
.wrapper{width:800px;margin:0 auto;padding-bottom:50px;} 
h2{height:50px;line-height:50px;font-size:22px;font-weight:normal;font-family:"Microsoft YaHei",SimHei;margin-bottom:20px;} 
/* focus */ 
#focus{width:800px;height:280px;overflow:hidden;position:relative;} 
#focus ul{height:380px;position:absolute;} 
#focus ul li{float:left;width:800px;height:280px;overflow:hidden;position:relative;background:#000;} 
#focus ul li div{position:absolute;overflow:hidden;} 
#focus .btnBg{position:absolute;width:800px;height:20px;left:0;bottom:0;background:#000;} 
#focus .btn{position:absolute;width:780px;height:10px;padding:5px 10px;right:0;bottom:0;text-align:right;} 
#focus .btn span{display:inline-block;_display:inline;_zoom:1;width:25px;height:10px;_font-size:0;margin-left:5px;cursor:pointer;background:#fff;} 
#focus .btn span.on{background:#fff;} 
#focus .preNext{width:45px;height:100px;position:absolute;top:90px;background:url(/upload/otherpic59/63007.png) no-repeat 0 0;cursor:pointer;} 
#focus .pre{left:0;} 
#focus .next{right:0;background-position:right top;}

JS代码（tupianqiehuan.js）：

$(function() { 
  var sWidth = $("#focus").width(); //获取焦点图的宽度（显示面积） 
  var len = $("#focus ul li").length; //获取焦点图个数 
  var index = 0; 
  var picTimer; 
   
  //以下代码添加数字按钮和按钮后的半透明条，还有上一页、下一页两个按钮 
  var btn = "