javascript 倒计时器 - 需要第二个数字

Question

我的老板交给了我一段现有的 javascript，并要求对其进行修改 - 问题是，我根本不知道如何处理 javascript - 我们的后端开发人员意外退出，而我只是想帮忙。

我需要让这个倒计时器始终显示两位数(01 而不是 1)。我在这里搜索并尝试了一些类似的问题解决方案，但它们都针对单个问题，而且我根本没有运气使用 if else if 语句进行更改(部分是因为我的 js 理解和语法不好。)希望对于知道自己在做什么的人来说这是一个简单的修复!提前致谢。

<script>
// creating a reusable CountDownTimer class with TargetDate

/*
 targetDate = Expiration date
 displayCountDownOnElement = on what element you need the countdown displayed at.
 hideOnExpire = on what element you need to hide when it expires.
*/
  var CountDownTimer = function(targetDate, displayCountDownOnElement, hideOnExpire){
  var target_date  = new Date(targetDate).getTime();
  var countdown = document.getElementById(displayCountDownOnElement);
  var hideExpire = document.getElementById(hideOnExpire);
  
  // variables for time units
  var days, hours, minutes, seconds;
  
  
  timer();
  setInterval(timer, 1000);
  function timer() {
 
      // 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 + " : " + hours + " : "
      + minutes + " : " + seconds + " ";  
    
      if(seconds_left < 0) { 
        hideExpire.style.display = "none";
        countdown.innerHTML = "";
      }
    
  }
}


// Sample Timer to Dec. 1, 2014 1:30:00 PM 
var c = new CountDownTimer("Dec 1, 2014 1:30:00 PM GMT -0800","cyber-timer", "cyber-timer");

</script>

此处演示:http://codepen.io/anon/pen/YPzwQg

Answer 1

只需添加以下内容:

  if(days < 10){days = "0" + days;}
  if(hours < 10){hours = "0" + hours;}
  if(minutes < 10){minutes = "0" + minutes;}
  if(seconds < 10){seconds = "0" + seconds;}

在此之前:

  // format countdown string + set tag value
  countdown.innerHTML = days + " : " + hours + " : "
  + minutes + " : " + seconds + " ";