目前我有一个脚本，它具有特定日期的倒计时，但我希望倒计时特定于计时器，所以让我们说如果我启动计时器并且我已设置计时器运行30天后，它将运行30天，然后再次重置为30天并开始运行。有可能改变它吗？
我的代码：
<body>
<span id="countdown"></span>
<script LANGUAGE="Javascript">
// set the date we're counting down to
var target_date = new Date("Apr 9, 2015").getTime();
// variables for time units
var days, hours, minutes, seconds;
// get tag element
var countdown = document.getElementById("countdown");
// update the tag with id "countdown" every 1 second
setInterval(function () {
// find the amount of "seconds" between now and target
var current_date = new Date().getTime();
var seconds_left = (target_date - current_date) / 1000;
// do some time calculations
days = parseInt(seconds_left / 86400);
seconds_left = seconds_left % 86400;
hours = parseInt(seconds_left / 3600);
seconds_left = seconds_left % 3600;
minutes = parseInt(seconds_left / 60);
seconds = parseInt(seconds_left % 60);
// format countdown string + set tag value
countdown.innerHTML = days + "d, " + hours + "h, "
+ minutes + "m, " + seconds + "s";
}, 1000);
</script>
</body>
编辑：
我现在已将代码更改为下方，但现在当我在浏览器中打开网站时，它是空白的。
新代码：
<span id="countdown"></span>
<script LANGUAGE="Javascript">
// set the date we're counting down to
var target_date = new Date("Apr 9, 2015").getTime();
// variables for time units
var days, hours, minutes, seconds;
// get tag element
var countdown = document.getElementById("countdown");
if (seconds_left <= 0){
target_date = target_date + 30 days;
}
// update the tag with id "countdown" every 1 second
setInterval(function () {
// find the amount of "seconds" between now and target
var current_date = new Date().getTime();
var seconds_left = (target_date - current_date) / 1000;
// do some time calculations
days = parseInt(seconds_left / 86400);
seconds_left = seconds_left % 86400;
hours = parseInt(seconds_left / 3600);
seconds_left = seconds_left % 3600;
minutes = parseInt(seconds_left / 60);
seconds = parseInt(seconds_left % 60);
// format countdown string + set tag value
countdown.innerHTML = days + "d, " + hours + "h, "
+ minutes + "m, " + seconds + "s";
}, 1000);
答案 0 :(得分：1)
我真的建议您利用JavaScript库，在您的情况下moment JS 是完美的解决方案，您可以查看他们的文档并了解如何轻松管理时间。无论如何，这里是使用时刻js的问题的解决方案。
首先下载片刻js并将其添加到您的页面。
<span id="days"> </span>
<span id="hours"></span>
<span id="minutes"></span>
<span id="seconds"></span>
它不能简单：）
//create two variables for holding the date for 30 back from now using substract
var back30Days = moment().subtract(30, 'days').format('YYYY-MM-DD H:mm:ss');
var countDownSeconds = Math.floor(moment().diff(back30Days, 'seconds'));
//variables holding days, hours , minutes and seconds
var Days, Minutes, Hours, Seconds;
// Set Interval function for performing all calculations and decrementing the countDownSeconds
setInterval(function () {
// Updating Days
Days = pad(Math.floor(countDownSeconds / 86400), 2);
// Updating Hours
Hours = pad(Math.floor((countDownSeconds - (Days * 86400)) / 3600), 2);
// Updating Minutes
Minutes = pad(Math.floor((countDownSeconds - (Days * 86400) - (Hours * 3600)) / 60), 2);
// Updating Seconds
Seconds = pad(Math.floor((countDownSeconds - (Days * 86400) - (Hours * 3600) - (Minutes * 60))), 2);
// Updation our HTML view
document.getElementById("days").innerHTML = Days + ' Days';
document.getElementById("hours").innerHTML = Hours + ' Hours';
document.getElementById("minutes").innerHTML = Minutes + ' Minutes';
document.getElementById("seconds").innerHTML = Seconds + ' Seconds';
// Decrement the countDownSeconds
countDownSeconds--;
// If we reach zero , our chrono should reset to 30 days back again, as you told
if (countDownSeconds === 0) {
countDownSeconds = Math.floor(moment().diff(back30Days, 'seconds'));
}
}, 1000);
// Function for padding the seconds i.e limit it only to 2 digits
function pad(num, size) {
var s = num + "";
while (s.length < size) s = "0" + s;
return s;
}