$.fn.extend 创建插件

<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <title>3-15</title>
   <script type="text/javascript" src="http://s.59iwh.com/js/jquery-1.10.2.min.js"></script>
   <script type="text/javascript" src="./lun.js"></script>
   <style type="text/css">
       .nav_nextad{ 283px;position:relative;text-align: center}
       .nextad_photo{position: absolute;overflow: hidden;margin: 0}
       .nextad_photo li{display: none;}
       .nextad_photo li a img{ 243px}
       .nextad_photo .showed{display: block}

       .nav{ 283px;position:relative;text-align: center;margin-left: 300px}
       .nextad{position: absolute;overflow: hidden;margin: 0}
       .nextad li{display: none;}
       .nextad li a img{ 243px}
       .nextad .showed{display: block}
   </style>
</head>
<body>
   <div class="nav_nextad">
        <ul class="nextad_photo">
            <li class="showed"><a class="showed"><img src="http://img.59iwh.com/rc/bce2c54e8239cadfc724963c572139e6.jpg">
            </a></li>
            <li class=""><a class="showed" ><img src="http://img.59iwh.com/rc/1882be0b4ceecffaf44f46392aff503e.jpg">
            </a></li>
        </ul>

    </div>

    <div class="nav">
        <ul class="nextad">
            <li class="showed"><a class=" showed" ><img src="http://img.59iwh.com/rc/bce2c54e8239cadfc724963c572139e6.jpg">
            </a></li>
            <li class=""><a class=" showed"><img src="http://img.59iwh.com/rc/1882be0b4ceecffaf44f46392aff503e.jpg">
            </a></li>
        </ul>

    </div>
</body>
<script type="text/javascript">
;(function($) {
   $.fn.extend({
       lun:function(t,time){
           var len = $("."+t).find('li').length;
           console.log(len);
            var index = 0; //页序号
            var adTimer;
            $("."+t).mouseover(function() {

            }).eq(0).mouseover();//滑入停止动画，滑出开始动画.

            $('.'+t).hover(function() {
                clearInterval(adTimer);
            }, function() {
                adTimer = setInterval(function() {
                    if (index == len) {
                        index = 0;
                    }
                    $("."+t).find('li').removeClass('showed').eq(index).addClass('showed');
                   index++;
                }, time);
            }).trigger("mouseleave");
       }
   });
})(jQuery);

   $(function(){
       var t = $(".nav_nextad").prop("className");
       $(".nav_nextad").lun(t,5000);

       var t = $(".nav").prop("className");
       $(".nav").lun(t,2000);
   })

</script>
</html>