一款js实现的文字滚动效果

<div id="marquees">
    <a href="#">你可曾有过无数的梦想，</a><br>
    <br>
    <a href="#">却在时光的流逝里幻灭 </a><br>
    <br>
    <a href="#">你可曾对未来期待憧憬，</a><br>
    <br>
    <a href="#">却在成长的岁月中迷失</a><br>
    <br>
</div>
<script language="JavaScript">

marqueesHeight = 200;
stopscroll = false;

with(marquees){
    style.width = 0;
    style.height = marqueesHeight;
    style.overflowX = "visible";
    style.overflowY = "hidden";
    noWrap = true;
    onmouseover = new Function("stopscroll=true");
    onmouseout = new Function("stopscroll=false");
}

document.write('<div id="templayer" style="position:absolute;z-index:1;visibility:hidden"></div>');

preTop = 0; currentTop = 0;

function init(){
    templayer.innerHTML="";
    while(templayer.offsetHeight<marqueesHeight){
      templayer.innerHTML += marquees.innerHTML;
    }
    marquees.innerHTML = templayer.innerHTML+templayer.innerHTML;
    setInterval("scrollUp()",20);//滚动的速度

}
document.body.onload = init;

function scrollUp(){
    if(stopscroll==true) return;
    preTop=marquees.scrollTop;
    marquees.scrollTop += 1;
    if(preTop==marquees.scrollTop){
      marquees.scrollTop = templayer.offsetHeight-marqueesHeight;
      marquees.scrollTop += 1;
    }
}
</script>