如何用js控件div的滚动条，让它在内容更新时自动滚到底部？

<script language="javascript">

function sendText()

{

var e=document.getElementById("div1")

var inp=document.getElementById("inp")

e.innerText=e.innerText+"\n"+inp.value;

//e.scrollTop=e.scrollHeight;

}

function sc()

{

var e=document.getElementById("div1")

e.scrollTop=e.scrollHeight;

}

var s=setInterval("sc()",200)

</script>

<div id="div1" style="border:1px #ff9966 dashed;width:400;height:100;overflow-x:hidden;overflow-y:scroll">

</div>

<input type="text" id="inp" style="width:300">

<input type="button" onclick="sendText()" value="发送">