用Javascript制作倒数计秒器

00:00:11:00 /* This notice must be untouched at all times. countdown.js v. 1.0 The latest version is available at http://blog.csdn.net/yjgx007 Copyright (c) 2004 Xinyi.Chen. All rights reserved. Created 7/30/2004 by Xinyi.Chen. Web: http://blog.csdn.net/yjgx007 E-Mail: [e-mail] Last modified: 7/30/2004 This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; See the GNU General Public License at http://www.gnu.org/copyleft/gpl.html for more details. */ var elapse = 100; var start = document.all("clock").innerText; var finish = "00:00:00:00"; var timer = null; function onTimer(i) { if (start == finish) { window.clearTimeout(timer); alert("time is reach!"); return; } var hms = new String(start).split(":"); var ms = new Number(hms[3]); var s = new Number(hms[2]); var m = new Number(hms[1]); var h = new Number(hms[0]); ms -= 10; if (ms

新建一个文本文件(后缀名是TXT)，然后将下面的源代码全部复制／粘贴到这个文本文件中，保存后改变这个文本文件的后缀名为HTML，然后在IE浏览器中打开并运行。

<span id="clock">00:00:11:00</span>
<input type=button value="start countdown!" onclick="onTimer()">
<input type=button value="stop countdown!" onclick="window.clearTimeout(timer);">
<script language="Javascript">
/* This notice must be untouched at all times.

countdown.js v. 1.0
The latest version is available at
http://blog.csdn.net/yjgx007

Copyright (c) 2004 Xinyi.Chen. All rights reserved.
Created 7/30/2004 by Xinyi.Chen.
Web: http://blog.csdn.net/yjgx007
E-Mail: [e-mail]
Last modified: 7/30/2004

This program is free software;
you can redistribute it and/or modify it under the terms of the
GNU General Public License as published by the Free Software Foundation;

See the GNU General Public License
at http://www.gnu.org/copyleft/gpl.html for more details.
*/
var elapse = 100;
var start = document.all("clock").innerText;
var finish = "00:00:00:00";
var timer = null;
function onTimer(i)
{

if (start == finish)
{
window.clearTimeout(timer);
alert("time is reach!");
return;
}

var hms = new String(start).split(":");
var ms = new Number(hms[3]);
var s = new Number(hms[2]);
var m = new Number(hms[1]);
var h = new Number(hms[0]);

ms -= 10;
if (ms < 0)
{
ms = 90;
s -= 1;
if (s < 0)
{
s = 59;
m -= 1;
}

if (m < 0)
{
m = 59;
h -= 1;
}
}

var ms = ms < 10 ? ("0" + ms) : ms;
var ss = s < 10 ? ("0" + s) : s;
var sm = m < 10 ? ("0" + m) : m;
var sh = h < 10 ? ("0" + h) : h;

start = sh + ":" + sm + ":" + ss + ":" + ms;
document.all("clock").innerText = start;

timer = window.setTimeout("onTimer()",elapse);
}
</script>

考虑到onTimer函数中执行语句的延迟，实际中你可以减少elapse的值，使得倒计数秒更为精确！