文字循环轮播

<div class="scroll1" id="demo">
    <div id="demo1">
       <ul id="js-list" class="js-lunbo">
           <li><span>王国1</span><span>2017-09-16</span><span>10:00:00</span></li>
           <li><span>王国2</span><span>2017-09-16</span><span>10:00:00</span></li>
           <li><span>王国3</span><span>2017-09-16</span><span>10:00:00</span></li>
           <li><span>王国4</span><span>2017-09-16</span><span>10:00:00</span></li>
           <li><span>王国5</span><span>2017-09-16</span><span>10:00:00</span></li>
           <li><span>王国6</span><span>2017-09-16</span><span>10:00:00</span></li>
           <li><span>王国7</span><span>2017-09-16</span><span>10:00:00</span></li> 
        </ul>
   </div>
   <ul id="demo2"></ul>
</div>

<script>
        var demo=document.getElementById("demo");
        var demo1=document.getElementById("demo1");
        var demo2=document.getElementById("demo2");
        demo2.innerHTML=demo1.innerHTML;
        //给demo1,demo2加相同的高度
        demo1.style.height=document.getElementById("js-list").offsetHeight+"px";
        demo2.style.height=demo1.offsetHeight+"px";
        //定时器，每隔50毫秒调用一次scrollup()函数，来实现文字的滚动
        var timer=window.setInterval("scrollup()",50);
        //定义函数
        function scrollup()
        {
            //如果demo滚上去的高度大于demo的高度，重新给demo赋值从0再开始滑动
            if(parseFloat(demo.scrollTop)>=document.getElementById("js-list").offsetHeight)
            {
                demo.scrollTop=0;
            }else
            {
                demo.scrollTop++;
            }
        }
</script>