js倒计时关闭窗口&计算字数

<script language="javascript">
//resizeTo(400, 300);

var secs = 3;
  for(i=1;i<=secs;i++) {
   window.setTimeout("update(" + i + ")", i * 1000);
  }
  function update(num) {
    if(num == secs) {
     
      if(window.opener.clicked != undefined){
       window.opener.clicked = false;
      }
      window.close();
    }
    else {
      printnr = secs-num;
      document.getElementById('closeLevel').innerHTML = "还剩下 "+printnr+" 秒关闭此窗口";
    }
  }
</script>


<input type="button" class="button" onclick="javascript:alert('帖子内容长度 ' + document.Form1.content.value.length +  '  个字,最多不能超过400个字！');" value="计算字数"/>