抢购代码

function newTimeRun(nowTime, beginTime, overTime,classname){
    var unStartTimeLength =   new Date(beginTime) - new Date(nowTime),//未开始的时间长度
    //var unStartTimeLength =   new Date(beginTime).getTime() - new Date(nowTime).getTime(),//未开始的时间长度
        endTimeLength = new Date(nowTime) - new Date(overTime),//已过期的时间长度
        timingLength =  new Date(overTime) -  new Date(nowTime);//抢购中的时间长度
    //未开始
    if(unStartTimeLength > 0){
        countDown(unStartTimeLength,function(time){
                var hour = formatNum(time[0] * 24 + time[1]),
                    min = formatNum(time[2]),
                    sec = formatNum(time[3]);
                classname.html('<span class="timeTxt">离特惠开始还剩 <span class="remain">' + hour + ':' + min + ':' + sec +'</span></span>')
            },
            function(){
                countDown(timingLength,function(time){
                    var hour = time[0] * 24 + time[1],
                        min = time[2],
                        sec = time[3];
                    classname.html('<span class="timeTxt">离特惠结束还剩 <span class="remain">' + hour + ':' + min + ':' + sec +'</span></span>');
                },function(){
                    classname.html('<span class="timeTxt">本场特惠已结束</span>');
                })
            });
    }
    //过期
    else if(endTimeLength >=0){
        classname.html('<span class="timeTxt">本场特惠已结束</span>');
    }
    //开始-结束
    else{
        countDown(timingLength,function(time){
            var hour = formatNum(time[0] * 24 + time[1]),
                min = formatNum(time[2]),
                sec = formatNum(time[3]);
            classname.html('<span class="timeTxt">离特惠结束还剩 <span class="remain">' + hour + ':' + min + ':' + sec +'</span></span>');
        },function(){
            classname.html('<span class="timeTxt">本场特惠已结束</span>');
        })
    }
} 

function countDown(times, fn, endFn) {
    if (typeof times === "number") {
        times = calculateTime(times);
    } else if (Object.prototype.toString.apply(times) === "[object Date]") {
        var ms = times.getTime() - new Date().getTime()
        times = calculateTime(ms);
        setTimeout(function () {
            countDown(times, fn, endFn);
        }, ms % 1000);
        return;
    }
    fn(times);    // 一开始先执行一次
    var intervalMac = setInterval(function () {
        var timesLen = times.length,
            scales = [24, 60, 60],
            scalesLen = scales.length;
        for (var i = timesLen; i--;) {
            if (times[i] > 0) {
                times[i] = times[i] - 1;
                break;
            }
            // 等于0，非首位的处理
            if (i !== 0) {
                times[i] = scales[scalesLen -(timesLen - i)] - 1;
            } else { // 一直到首位都为0，倒计时结束
                for (var j = 0; j < times.length; j++) {
                    times[j] = 0;
                }
                clearInterval(intervalMac);
                return;
            }
        }
        fn(times);
        if(typeof endFn === "function"){
            var isEnd = true;
            for(var i = 0,len = times.length;i < len;i++){
                if(times[i] !== 0){
                    isEnd = false;
                    break;
                }
            }
            if(isEnd){
                endFn(times);
            }
        }
    }, 1000);
}
//把毫秒转换成数组[day, hour, minute, second]
function calculateTime(time) {
    if (time < 0) {
        return [0, 0, 0, 0];
    }
    time = Math.floor(time / 1000);
    var times = [], scales = [86400, 3600, 60];
    for (var i = 0; i < scales.length; i++) {
        times.push(Math.floor(time / scales[i]));
        time %= scales[i];
    }
    times.push(time);
    return times;
}

调用

$(".box3").each(function(i,elem){
    var date = new Date();

    var uStartTime = $(elem).attr("zy-s-time"),
        uEndTime = $(elem).attr("zy-e-time"),
        timeSpan = $(".timeW",elem);
    newTimeRun(date,uStartTime,uEndTime,timeSpan);
})

注意时间格式