zk执行本地脚本以及使用Jquery设置滚动条保持在底端

<div id="viewerDiv"  style="overflow-x:hidden;overflow-Y:scroll;" height="120px"/>
<div>
<image src="/image/InstantMessage/sendbutt.png"
            id="sendBtn" onClick='Clients.evalJavaScript("sc()")'/>
</div>

<script type="text/javascript">
      <![CDATA[ 
      function sc()
      {
       var $d=jq("$viewerDiv");
       $d.scrollTop($d.height());}
      
       ]]> 
     </script>