jquery 实现滚屏 轮播

<script type="text/javascript">  
$(document).ready(function(){
    $("#start").click(function(){
        if($("#box:animated").length==0)就是这句话
        {
            $("#box").animate({height:300},"slow");
            $("#box").animate({width:300},"slow");
            $("#box").animate({height:100},"slow");
            $("#box").animate({width:100},"slow");
        }
    });
});
</script>