js按钮显示时间

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

 <head>

  <title> New Document </title>

  <meta name="Generator" content="EditPlus">

  <meta name="Author" content="">

  <meta name="Keywords" content="">

  <meta name="Description" content="">

<script language="javascript"> 

<!--

var wait_time = 8; //设置秒数(单位秒) 

var secs_time = 0;        

for(var i=1;i<=wait_time;i++)

{ 

window.setTimeout("sTimer("+i+")",i*1000); 

} 

function sTimer(num) 

{  

if(num==wait_time)  

{ 

document.getElementById("reg_btn").value=" 同意注册 ";  

document.getElementById("reg_btn").disabled=false;  

}  

else

{

secs_time=wait_time-num;   

document.getElementById("reg_btn").value="请先阅读服务条款 ("+secs_time+")";  

}

} 

//--> 

 

</script> 

 </head>

 

 <body>

<div style="width:350px; text-align:center;">

<form name="regForm" method="post" action=""> 

<input type="submit" value="请先阅读服务条款 (0)" disabled="disabled" id="reg_btn">

<input id="BtnClose" type="button" value=" 我不同意 " onclick="window.close();"> 

</form>

</div> 

 </body>

</html>