javascript定时触发

用javascript写个定时器，定时触发某个特定功能：

<input name="txtTimer" value="10秒">
<script LANGUAGE=javascript>

<!--
function setup(cmd) {
$('#_form').attr('action', 'pipe_setup.do');
$('input[name=cmd]').val(cmd);
$('#_form').submit();
}
waitTime=10000; //10 秒

timer=setInterval("OnTimer()",1000); 
function OnTimer(){ 
waitTime=waitTime-1000; 
if(waitTime==0){ 
setup('GetFrame');
}
txtTimer.value=waitTime/1000+"秒"; 
}
//-->
</SCRIPT>