一、故事背景：
1. 今天公司有个项目需求
2. 在前端页面实现一个倒计时功能
3. 初步设想：后端根据需求规定一个未来的时间，前端根据当前时间进行计算
4. 然后将时间格式化，时分秒的格式
5. 时间倒计时完成，刷新页面获取最新的页面
6. 最后在前端展示；大致是这样
二、上代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<div class="js_time_txt">
</div>
<script src="./jquery-3.3.1.min.js"></script>
<script>
$(function () {
// 倒计时
var _ordertimer = null;
var data = new Date();
var txt = $('.js_time_txt');
var buyTime = '2018-09-20 22:25:59'; //开抢时间
var nowTime = '2018-09-20 22:23:45'; //接口返回当前时间
var dateDiff = new Date(nowTime) - new Date(getnow()); //请求时间戳与本地时间戳
if (dateDiff < 0) {
dateDiff = Math.abs(dateDiff);
}
if (new Date(nowTime) > new Date(buyTime)) {
$('.time-range').hide(); //已开枪
return;
} else {
leftTimer(buyTime);
_ordertimer = setInterval(function () {
leftTimer(buyTime)
}, 1000);
}
// 获取当前时间 xxxx/xx/xx 00:00:00
function getnow() {
var year = data.getFullYear();
var month = parseInt(data.getMonth() + 1) >= 10 ? parseInt(data.getMonth() + 1) : '0' + parseInt(data.getMonth() + 1);
var day = data.getDate();
var hours = data.getHours();
var minutes = data.getMinutes();
var seconds = data.getSeconds();
var now = year + '/' + month + '/' + day + ' ' + hours + ':' + minutes + ':' + seconds;
return now;
}
function leftTimer(enddate) {
var leftTime = (new Date(enddate)) - new Date + dateDiff;
var days = parseInt(leftTime / 1000 / 60 / 60 / 24, 10); //计算剩余的天数
var hours = parseInt(leftTime / 1000 / 60 / 60 % 24, 10); //计算剩余的小时
var minutes = parseInt(leftTime / 1000 / 60 % 60, 10);//计算剩余的分钟
var seconds = parseInt(leftTime / 1000 % 60, 10);//计算剩余的秒数
days = checkTime(days);
hours = checkTime(hours);
minutes = checkTime(minutes);
seconds = checkTime(seconds);
if (days >= 0 || hours >= 0 || minutes >= 0 || seconds >= 0)
txt.html(days + "天" + hours + "小时" + minutes + "分" + seconds + "秒");
if (days <= 0 && hours <= 0 && minutes <= 0 && seconds <= 0) {
window.clearInterval(_ordertimer);
_ordertimer = null;
}
}
function checkTime(i) { //将0-9的数字前面加上0，例1变为01
if (i < 10) {
i = "0" + i;
}
return i;
}
})
</script>
</body>
</html>