javascript - 在 HH :MM:SS instead of H:M:S in Javascript 中显示倒计时器

Question

我设法以 H:M:S 格式显示倒计时器。

请问如何将其显示为 HH:MM:SS 格式？例如，假设 300 小时 1 分 1 秒，它将显示为 300:01:01 而不是 300:1:1 。

这就是我到目前为止所得到的。

// Set the date we're counting down to
var countDownDate = new Date("Aug 31, 2019 22:55:00").getTime();

// Update the count down every 1 second
var x = setInterval(function() {

  // Get todays date and time
  var now = new Date().getTime();

  // Find the distance between now and the count down date
  var distance = countDownDate - now;

  // Time calculations for days, hours, minutes and seconds
  var hours = Math.floor(distance / (1000 * 60 * 60));
  var minutes = Math.floor((distance % (1000 * 60 * 60)) / (1000 * 60));
  var seconds = Math.floor((distance % (1000 * 60)) / 1000);

  // Display the result in the element with id="demo"
  document.getElementById("demo").innerHTML = hours + " : "
  + minutes + " : " + seconds + "";

  // If the count down is finished, write some text 
  if (distance < 0) {
    clearInterval(x);
    document.getElementById("demo").innerHTML = "EXPIRED";
  }
}, 1000);

<p id="demo"></p>

Answer 1

测试小于 10 的值并附加前导零

// Set the date we're counting down to
var countDownDate = new Date("Aug 31, 2019 22:55:00").getTime();

// Update the count down every 1 second
var x = setInterval(function() {

  // Get todays date and time
  var now = new Date().getTime();

  // Find the distance between now and the count down date
  var distance = countDownDate - now;

  // Time calculations for days, hours, minutes and seconds
  var hours = Math.floor(distance / (1000 * 60 * 60));
  var minutes = Math.floor((distance % (1000 * 60 * 60)) / (1000 * 60));
  var seconds = Math.floor((distance % (1000 * 60)) / 1000);

  if (hours < 10) hours = '0'+ hours;
  if (minutes < 10) minutes = '0'+ minutes;
  if (seconds < 10) seconds = '0'+ seconds;

  // Display the result in the element with id="demo"
  document.getElementById("demo").innerHTML = hours + " : "
  + minutes + " : " + seconds + "";

  // If the count down is finished, write some text 
  if (distance < 0) {
    clearInterval(x);
    document.getElementById("demo").innerHTML = "EXPIRED";
  }
}, 1000);

<p id="demo"></p>

正如 kamoroso94 在评论中提到的，您还可以使用 padstart()

// Set the date we're counting down to
var countDownDate = new Date("Aug 31, 2019 22:55:00").getTime();

// Update the count down every 1 second
var x = setInterval(function() {

  // Get todays date and time
  var now = new Date().getTime();

  // Find the distance between now and the count down date
  var distance = countDownDate - now;

  // Time calculations for days, hours, minutes and seconds
  var hours = Math.floor(distance / (1000 * 60 * 60));
  var minutes = Math.floor((distance % (1000 * 60 * 60)) / (1000 * 60));
  var seconds = Math.floor((distance % (1000 * 60)) / 1000);

  // Display the result in the element with id="demo"
  document.getElementById("demo").innerHTML = hours.toString().padStart(2, '0') + " : "
  + minutes.toString().padStart(2, '0') + " : " + seconds.toString().padStart(2, '0') + "";

  // If the count down is finished, write some text 
  if (distance < 0) {
    clearInterval(x);
    document.getElementById("demo").innerHTML = "EXPIRED";
  }
}, 1000);

<p id="demo"></p>