javascript实现抢购倒计时程序

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 <mce:script type="text/javascript"><!-- 
 //抢票起始时间 2011年2月29日10点10分0秒，月份的定义从0开始，因此1表示2月份。 
 var start = new Date('2011', '1', '29', '10', '10', '00'); 
 //var start = new Date('2011','1', '28', '15', '10', '00'); 
 
 //抢票截止时间 2011年2月29日11点10分59秒 
 var expire = new Date('2011', '1', '29', '11', '10', '59'); 
 
 //显示倒计时的HTML对象 
 var clock = document.getElementById('clientclock'); 
 
 //倒计时函数，每秒执行一次 
 setLeftTime(); 
 
 function setLeftTime() { 
 
 var now = new Date(); 
 
 //如果当前时间小于抢票起始时间，那么显示：抢票倒计时××天××时××分××秒 
 if (now < start) { 
 var diff = -480 - now.getTimezoneOffset() //是北京时间和当地时间的时间差 
 var lefttime = (start.getTime() - now.getTime()) + diff * 60000 
 var day = Math.floor(lefttime / (1000 * 60 * 60 * 24)); 
 var hour = Math.floor(lefttime / (1000 * 3600)) - (day * 24); 
 var minute = Math.floor(lefttime / (1000 * 60)) - (day * 24 * 60) - (hour * 60); 
 var second = Math.floor(lefttime / (1000)) - (day * 24 * 60 * 60) - (hour * 60 * 60) - (minute * 60); 
 
 clock.innerHTML = '抢票倒计时：<span class="ztCopy">' + day + '</span>天&nbsp;<span class="ztCopy">' + hour + '</span>时&nbsp;<span class="ztCopy">' + minute + '</span>分&nbsp;<span class="ztCopy">' + second + '</span>秒'; 
 } 
 //如果当前时间大于等于抢票起始时间，小于抢票截止时间，即：正在抢票，那么显示：抢票还剩××天××时××分××秒 
 else if (now <= expire) { 
 var diff = -480 - now.getTimezoneOffset() //是北京时间和当地时间的时间差 
 var lefttime = (expire.getTime() - now.getTime()) + diff * 60000 
 var day = Math.floor(lefttime / (1000 * 60 * 60 * 24)); 
 var hour = Math.floor(lefttime / (1000 * 3600)) - (day * 24); 
 var minute = Math.floor(lefttime / (1000 * 60)) - (day * 24 * 60) - (hour * 60); 
 var second = Math.floor(lefttime / (1000)) - (day * 24 * 60 * 60) - (hour * 60 * 60) - (minute * 60); 
 
 clock.innerHTML = '抢票还剩：<span class="ztCopy">' + day + '</span>天&nbsp;<span class="ztCopy">' + hour + '</span>时&nbsp;<span class="ztCopy">' + minute + '</span>分&nbsp;<span class="ztCopy">' + second + '</span>秒'; 
 } 
 //如果当前时间大于抢票截止时间，即：本轮抢票结束，那么显示：本轮抢购结束 
 else { 
 clock.innerHTML = '本轮抢购结束'; 
 } 
 
 setTimeout("setLeftTime()", 1000); 
 } 

// --></mce:script>