Building a Countdown Timer

Countdown Timer

Calculate remaining time by subtracting Date.now() from a future timestamp, then extract days, hours, minutes, and seconds.

Example

function getCountdown(targetDate) {
  const diff = new Date(targetDate) - Date.now();
  if (diff <= 0) return { expired: true };
  return {
    days:    Math.floor(diff / 86400000),
    hours:   Math.floor((diff % 86400000) / 3600000),
    minutes: Math.floor((diff % 3600000)  / 60000),
    seconds: Math.floor((diff % 60000)    / 1000),
  };
}

setInterval(() => {
  const { days, hours, minutes, seconds } = getCountdown("2025-01-01");
  display.textContent = `${days}d ${hours}h ${minutes}m ${seconds}s`;
}, 1000);

JAVASCRIPT

Full Editor

Pro Tip

Update countdown timers every second with setInterval — clear the interval when the timer expires.

Related Resources

JavaScript Reference

Complete tag & property list

JavaScript How-To Guides

Step-by-step practical guides

JavaScript Exercises

Practice what you've learned