How many seconds till tomorrow?

Create a function getSecondsToTomorrow() that returns the number of seconds till tomorrow.

For instance, if now is 23:00, then:

getSecondsToTomorrow() == 3600

P.S. The function should work at any day, the “today” is not hardcoded.

To get the number of milliseconds till tomorrow, we can from “tomorrow 00:00:00” substract the current date.

First, we generate that “tomorrow”, and then do it:

function getSecondsToTomorrow() {
  let now = new Date();

  // tomorrow date
  let tomorrow = new Date(now.getFullYear(), now.getMonth(), now.getDate()+1);

  let diff = tomorrow - now; // difference in ms
  return Math.round(diff / 1000); // convert to seconds
}

Alternative solution:

function getSecondsToTomorrow() {
  let now = new Date();
  let hour = now.getHours();
  let minutes = now.getMinutes();
  let seconds = now.getSeconds();
  let totalSecondsToday = (hour * 60 + minutes) * 60 + seconds;
  let totalSecondsInADay = 86400;

  return totalSecondsInADay - totalSecondsToday;
}

Please note that many countries have Daylight Savings Time (DST), so there may be days with 23 or 25 hours. We may want to treat such days separately.