jquery无缝向上滚动实现代码

$(function(){
var $this = $(".renav");
var scrollTimer;
$this.hover(function(){
clearInterval(scrollTimer);
},function(){
scrollTimer = setInterval(function(){
scrollNews( $this );
}, 2000 );
}).trigger("mouseout");
});
function scrollNews(obj){
var $self = obj.find("ul:first");
var lineHeight = $self.find("li:first").height();
$self.animate({ "margin-top" : -lineHeight +"px" },600 , function(){
$self.css({"margin-top":"0px"}).find("li:first").appendTo($self);
})
}