JS实现考试管理系统中的倒计时（精确到时、分、秒）
??????? 使用JS实现这个小程序，其实还是比较简单的，主要用到了window对象中的setTimeout()方法和clearTimeout()方法，其它的便是关于时、分、秒算法的问题，方法有很多，在这里我只采用其中一种比较简单的方法。
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<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme() + "://"+ request.getServerName() + ":" + request.getServerPort()+ path + "/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><base href="<%=basePath%>"><title>My JSP 'demo4.jsp' starting page</title><meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0"><meta http-equiv="keywords" content="keyword1,keyword2,keyword3"><meta http-equiv="description" content="This is my page"><!--<link rel="stylesheet" type="text/css" href="styles.css">--><script type="text/javascript">var vartime, h, m, s, hstr, mstr, sstr;var xtime = 1.5 * 60 * 60;function timeclock() {if (xtime >= 0) {h = parseInt(xtime / 3600);m = parseInt((xtime % 3600) / 60);s = (xtime % 3600) % 60;hstr = h < 10 ? ("0" + h) : h;mstr = m < 10 ? ("0" + m) : m;sstr = s < 10 ? ("0" + s) : svartime = hstr + ":" + mstr + ":" + sstr;document.getElementById("timer").value = vartime;xtime--;setTimeout("timeclock();", 1000);} else {clearTimeout("timeclock();")var flag = confirm("时间到，单击“确定”以提交");if (flag) {document.forms[0].submit();} else {window.close("./demo.jsp");}}}</script></head><body><center><form action="./index.jsp" method="post">剩余时间：<input type="text" id="timer" name="txt" size="4"readonly="readonly" /> <input type="button" value="开始" onclick="timeclock();" /></form></center></body></html>?