按钮可用状态倒计时...

今天在一个网站注册的时候, 看到了在服务条款和声明的时候, 我同意这个按钮要等几秒钟才可用, 虽然以前也看到过, 但这几天实在是闲着无聊, 所以, 嘿, 咱也来一个吧.

<form name="frm">
<input type="submit" name="btnSubmit" value="我同意" />
</form>

<script language="javascript">
<!--
var sec = 9;
var wait = sec * 1000;
document.frm.btnSubmit.value = "我同意[" + sec + "]";
document.frm.btnSubmit.disabled = true;

for(var i = 0; i <= sec; i++) {
 window.setTimeout("TimeUpdate(" + i + ")", i * 1000);
}

window.setTimeout("TimeOk()", wait);

function TimeUpdate(num) {
 if(num != sec) {
  var pntNum = (wait / 1000) - num;
  document.frm.btnSubmit.value = "我同意[" + pntNum + "]";
 }
}

function TimeOk() {
 document.frm.btnSubmit.value = "我同意";
 document.frm.btnSubmit.disabled = false;
}
//-->
</script>

唉.无聊之极!!!!!!!!!!!!!!!!!!!!!!