Javascript: Trying to create a HH:MM:SS countdown from a Unix timestamp

Question

I have a Unix timestamp that comes back from the server when an item is created and my goal is to 'expire' the item after 24 hours.. I am trying to make a countdown function that will convert the Unix timestamp into HH:MM:SS format and countdown from 24 hours (Current browser time - the unix timestamp converted).

Answer 1

I think this is what you are looking for:

String.prototype.toHHMMSS = function() {
  var sec_num = parseInt(this, 10);
  var hours = Math.floor(sec_num / 3600);
  var minutes = Math.floor((sec_num - (hours * 3600)) / 60);
  var seconds = sec_num - (hours * 3600) - (minutes * 60);

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


let startTime = ((new Date()).getTime() / 1000) + 86400; // database unix-timestamp value
setInterval(() => {
  let curTime = (new Date()).getTime() / 1000;
  document.getElementById("timer").innerText = (`${startTime-curTime}`).toHHMMSS();
}, 1000);

<div id="timer"></div>

Hope this helps,