&#106avascript倒计时器 - 采用系统时间自校验

&#106avascript倒计时器 - 采用系统时间自校验(2) 码的执行时间以及显示时间所产生的延迟, 这次利用系统时间自校验倒计时, 无需手工调校使得倒计时更为精确, 代码及详细注释如下:

<span id="clock">00:01:11:00</span>
<input id="startB" type="button" value="start countdown!" onclick="run()">
<input id="endB" type="button" value="stop countdown!" onclick="stop()">
<br>
<input id="diff" type="text">
<input id="next" type="text">
<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: chenxinyi1978@hotmail.com
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 normalelapse = 100;
var nextelapse = normalelapse;
var counter;
var startTime;
var start = clock.innerText;
var finish = "00:00:00:00";
var timer = null;

// 开始运行
function run() {
  startB.disabled = true;
  endB.disabled = false;
  counter = 0;
  // 初始化开始时间
  startTime = new Date().valueOf();

  // nextelapse是定时时间, 初始时为100毫秒
  // 注意setInterval函数: 时间逝去nextelapse(毫秒)后, onTimer才开始执行
  timer = window.setInterval("onTimer()", nextelapse);
}

// 停止运行
function stop() {
  startB.disabled = false;
  endB.disabled = true;
  window.clearTimeout(timer);
}

window.onload = function() {
  endB.disabled = true;