js公告轮播代码

//首页公告
var $announcement = $('#announcement ul');
	var cheight = parseInt($('#announcement').css('line-height').split('p')[0]);
	var announcementLength = $announcement.find('li').length;
	var nowtop,nexttop;
	var announcementTimer = setInterval(function (){
		nowtop = parseInt($announcement.css('top').split('p')[0]);
		nexttop = 0;
		if(nowtop == (-(announcementLength - 1)*cheight)){
			nexttop = '0px';
		}else{
			nexttop = (nowtop - 30) + 'px';
		}
		console.log(nowtop + ' ' + (-(announcementLength - 1)*cheight));
		$announcement.animate({top:''+nexttop});
	},2000);

        

            
欢迎来到官方网站1！
            
欢迎来到官方网站2！
            
欢迎来到官方网站3！
            
欢迎来到官方网站4！
        
    

#announcement{ position:absolute; right:0; top:100px; width:300px; height:30px; line-height:30px; overflow:hidden;}
#announcement ul{ position:absolute; top:0;}
#announcement li{ height:30px; line-height:30px; overflow:hidden;}