Calculate countdown in days, hours, minutes and seconds | https://geeksforgeeks.org/create-countdown-timer-using-javascript/

calculate-countdown.js

/**
 * Calculate countdown in days, hours, minutes and seconds.
 *
 * @author Nick Freear, 06-May-2022.
 *
 * @see https://geeksforgeeks.org/create-countdown-timer-using-javascript/
 */

console.log('Countdown:', calcCountdown('2022-05-19'));
console.log('Countdown:', calcCountdown('dec 31, 2022 00:00:00.000 '));
console.log('Countdown:', calcCountdown('19/05/2022')); // Throws error!

function calcCountdown (deadlineStr) {
  const deadline = new Date(deadlineStr).getTime();
  const now = new Date().getTime();
  const diff = deadline - now;

  if (isNaN(deadline)) {
    throw new Error(`Input not recognized as a date-time: '${deadlineStr}'`);
  }

  const days = Math.floor(diff / (1000 * 60 * 60 * 24));
  const hours = Math.floor((diff % (1000 * 60 * 60 * 24)) / (1000 * 60 * 60));
  const minutes = Math.floor((diff % (1000 * 60 * 60)) / (1000 * 60));
  const seconds = Math.floor((diff % (1000 * 60 )) / 1000);

  return { days, hours, minutes, seconds, deadline: deadlineStr, diff, expired: diff < 0 };
}

// End.