聊天窗口 滚动条置底

function setBottom(){var div = document.getElementById('outputArea');div.scrollTop = div.scrollHeight; }

<div id="msg" style="width: 420px; height: 150px; overflow-y: scroll; border: 1px solid #999; overflow: auto; background-color: #FFFFFF">  </div>    <input type="button" value="发送" onclick="javascript:setBottom();">