Javascript ile Geriye Doğru Sayma

<script type="text/javascript">
var newCount;
function timer(position,count)
 {
  if (position == 'start') {
   document.getElementById("timer").innerHTML=count
   newCount = count - 1
   setTimeout("timer('go',newCount)",1000)
  }
 
  if (position == 'go') {
   document.getElementById("timer").innerHTML=count
   newCount--;
   setTimeout("timer('go',newCount)",1000)
  }
 }
</script>  <div id="timer" />