Reload a browser tab in the nearest X seconds

reloadInSeconds.js

(function reloadInSeconds () {
  const s = parseInt(prompt('Reload in nearest Nth second, where N is:'), 10);
  if (isNaN(s)) return;
	const ms = s * 1e3;
  const now = Date.now();
  const reloadAtTs = (Math.ceil(now / ms) + 1) * ms;
  console.info('Reloading at', new Date(reloadAtTs).toLocaleString());
  const countdownTick = () => {
    const timeleft = reloadAtTs - Date.now();
    const reloadInRounded = Math.round(timeleft/1e3);
    if (reloadInRounded > 0) {
        console.info(`Reloading in ${reloadInRounded}s`);
        return;
    }
    clearInterval(countdownInterval);
  };
  const countdownInterval = setInterval(countdownTick, 1e3);
  setTimeout(() => {
    console.info('Reloading…');
    window.location.reload();
  }, reloadAtTs - now);
})();