项目中用到了，简单整理在这

更新：

一开始从服务器获取的是时间点，然后根据本地时间求得差值显示倒计时，一开始这么做我是内心拒绝的(这样修改本机时间就会显示正在抢购了，但是无法下单后台有控制)，但是接口是这么给的，而且抢购活动页以前的开发也是这么做的，所以就按照当时的接口写的，测试的时候正好测试发现了这个问题，产品拍板改！然后改成了从服务器获取时间段的方法处理倒计时。

var rushtime = $("#rushTime").attr("value");//活动状态

var longtime = $("#longTime").attr("value");//当前活动状态下的活动时长

var rushdiscount = $("#rushDiscount").attr("value");//折扣

var begintoend = $("#beginToEnd").attr("value");//活动从开始到结束的全部持续时间

var countprice = $("#countprice").attr("value");//价格

if(rushtime == 1 || rushtime == 2){

//活动未开始,活动进行中

countDown(longtime,rushtime,begintoend);

}else if(rushtime == 3){

//活动已结束

$("#qianggou").show().html("活动已结束");

}else{

//没有活动

$("#qianggou").hide();

}

function countDown(longtime,rushtime,begintoend){

var time = longtime;

time = parseInt(time / 1000);

var day = Math.floor(time / (60*60*24));

time -= day * (60*60*24);

var hour = Math.floor(time /(60*60));

time -= hour * (60*60);

var minute = Math.floor(time / 60);

var second = time - (minute * 60);

if(day<10){

if(day<0 && rushtime == 1){

// 切换到正在抢购

rushtime = 2;

window.setTimeout(function(){countDown(begintoend,rushtime,begintoend);},1000);

}else if(day<0){

$("#qianggou").show().html("活动已结束");

$(".preprice1").html("").hide();

return;

}else{

day="0"+day;

}

}

if(hour<10){

hour="0"+hour;

}

if(minute<10){

minute="0"+minute;

}

if(second<10){

second="0"+second;

}

if(rushtime == 2){

$(".preprice1 i").html((countprice*rushdiscount).toFixed(2));

$(".preprice1").show();

}

if(rushtime == 1 && day==0&&hour==0&&minute==0&&second==1){

$("#qianggou").show().html("距离抢购还有   "+day+"天"+hour+"时"+minute+"分"+second+"秒");

rushtime = 2;

window.setTimeout(function(){countDown(begintoend,rushtime,begintoend);},1000);

}else if(rushtime == 1){

$("#qianggou").show().html("距离抢购还有   "+day+"天"+hour+"时"+minute+"分"+second+"秒");

longtime = longtime-1000;

window.setTimeout(function(){countDown(longtime,rushtime,begintoend);},1000);

}else if(day==0&&hour==0&&minute==0&&second==0){

$("#qianggou").show().html("活动已结束");

$(".preprice1").html("").hide();

return;

}else{

$("#qianggou").show().html("限时抢购剩余   "+day+"天"+hour+"时"+minute+"分"+second+"秒");

longtime = longtime-1000;

window.setTimeout(function(){countDown(longtime,rushtime,begintoend);},1000);

}

}

旧的代码

//dateend是活动结束日期事件戳

function countDown(dateend){

var now = Date.parse(new Date());

var str = dateend;

var target = Date.parse(new Date(str));

var time = target - now;

time = parseInt(time / 1000);

var day = Math.floor(time / (60*60*24));

time -= day * (60*60*24);

var hour = Math.floor(time /(60*60));

time -= hour * (60*60);

var minute = Math.floor(time / 60);

var second = time - (minute * 60);

if(day<10){

if(day<0){

$("#buy").html("活动已结束");

return;

}else{

day="0"+day;

}

}

if(hour<10){

hour="0"+hour;

}

if(minute<10){

minute="0"+minute;

}

if(second<10){

second="0"+second;

}

if(day==0&&hour==0&&minute==0&&second==0){

$("#buy").html("活动已结束");

}else{

$("#buy").html("限时抢购剩余"+day+"天"+hour+"时"+minute+"分"+second+"秒");

}

window.setTimeout(function(){countDown(dateend);},1000);

}