上下滚动广告

(function($){

    $.fn.extend({

        rollList:function(option){

            option=$.extend({

                direction:"up",

                step:1,

                time:23

            },option);

            var step_coe,scroll_coe,score_coe;

            if(option.direction=="up")

            {

                step_coe=1;

                scroll_coe=1;

                score_coe=1;

            }else

            {

                step_coe=-1;

                scroll_coe=-1;

                score_coe=0;

            }

            return this.each(function(){

                var $this=$(this);

                var _this=this;

                var itemHeight;

                var temp=$("
 
   

    
   
 
   
");

                $this.css("overflow","hidden").children()

                    .appendTo(temp);

                $this.append(temp.clone(true)).append(temp);

                itemHeight=$this.children();

                itemHeight=itemHeight.eq(1).offset().top-itemHeight.eq(0).offset().top;

                while($this.children(":last").offset().top-$this.offset().top<=$this.height())

                    $this.append(temp.clone(true));

                var roll;

                this.scrollTop=itemHeight*(1-score_coe);

                roll=function (){

                    temp=setInterval(function(){

                        if(_this.scrollTop*scroll_coe>=itemHeight*score_coe)

                        {	

                        _this.scrollTop=(_this.scrollTop-itemHeight)*scroll_coe;

                        }

                        _this.scrollTop+=option.step*step_coe;



                    },option.time);

                }

                $this.hover(function(){

                    clearInterval(temp);

                },function(){

                    roll();	

                });

                roll();

            });

        }		

    })

}(jQuery));

调用如下：
$(elem).rollList();