Function that formats number of seconds to total time (days, hours, minutes and seconds)

Question

I need to format total number of seconds to total time in the following format: Days:Hours:Minutes:Seconds.

This is what I did:

function formatTime(totalSeconds) {
  let days = Math.floor(totalSeconds / 86400);
  let hours = Math.floor((totalSeconds - (days * 86400)) / 3600);
  let minutes = Math.floor((totalSeconds / 60) % 60);
  let seconds = totalSeconds % 60;

  days = days < 10 ? `0${days}` : days;
  hours = hours < 10 ? `0${hours}` : hours;
  minutes = minutes < 10 ? `0${minutes}` : minutes;
  seconds = seconds < 10 ? `0${seconds}` : seconds;

  let formattedString = `${days}:${hours}:${minutes}:${seconds}`;
  return formattedString;
}

console.log(formatTime(5000));

Is this OK? Or there can be a better way?

Answer 1

Is it OK: yes, it works.

It could be slightly cleaner.

• I might create a const SEC_IN_HR = 3600 so that others can easily follow exactly what each equation is doing (this could be expanded to include SEC_IN_MIN and HR_IN_DAY).
• hours is calculated correctly, but if you wanted to stick to the pattern of not referring to time variables (day, hour, etc) you could use Math.floor(totalSeconds % (SEC_IN_HR*24) / SEC_IN_HR)
• minutes could also be re-written Math.floor(totalSeconds % SEC_IN_HR / 60)
• because time variables are initially numbers, but end up strings, you could do the conversion earlier and then use padStart(2,'0')
• formattedString is declared but unused, just return the formatted string, no need to declare the variable
• you could have time variables initialized in a list [dayStr, hourStr,..], then use padStart in map, and a join(':') at the return if you wanted shorter code, though it wouldn't be clearer

const SEC_IN_HR = 3600;
function formatTime(totalSeconds) {
  const days = `${Math.floor(totalSeconds / (SEC_IN_HR*24))}`;
  const hours = `${Math.floor(totalSeconds % (SEC_IN_HR*24) / SEC_IN_HR)}`;
  const minutes = `${Math.floor(totalSeconds % SEC_IN_HR / 60)}`;
  const seconds = `${Math.floor(totalSeconds % 60)}`;

  return `${days.padStart(2,'0')}:${hours.padStart(2,'0')}:${minutes.padStart(2,'0')}:${seconds.padStart(2,'0')}`;
}

console.log(formatTime(5000));

Shorter code

const SEC_IN_HR = 3600;
function formatTime(totalSeconds) {
  let timeStr = [
    `${Math.floor(totalSeconds / (SEC_IN_HR*24))}`,
    `${Math.floor(totalSeconds % (SEC_IN_HR*24) / SEC_IN_HR)}`,
    `${Math.floor(totalSeconds % SEC_IN_HR / 60)}`,
    `${Math.floor(totalSeconds % 60)}`
  ]; // this could be on one line

  return timeStr.map(s=>s.padStart(2,'0')).join(':');
}

console.log(formatTime(5000));

Answer 2

Instead of doing all the math yourself, here's an alternate way to do unit conversions.

I also included a function for zero-padding the numbers to cut down on code repetition.

function zeroPad(number) {
    return String(number).padStart(2, '0')
}

function formatTime(totalSeconds) {
  const second = 1
  const minute = 60*second
  const hour = 60*minute
  const day = 24*hour

  let remainingTime = totalSeconds
  const days = Math.floor(remainingTime/day)
  remainingTime -= days*day
  const hours = Math.floor(remainingTime/hour)
  remainingTime -= hours*hour
  const minutes = Math.floor(remainingTime/minute)
  remainingTime -= minutes*minute
  const seconds = remainingTime/second
  const secondsZPad = seconds < 10 ? `0${seconds}` : seconds;

  let formattedString = `${zeroPad(days)}:${zeroPad(hours)}:${zeroPad(minutes)}:${secondsZPad}`;
  return formattedString;
}

console.log(formatTime(4988.75));

Semantically, multiplying a number by the defined unit (hour = 60*minute) applies the unit to the value and dividing (for example, secondsInDay = 1*day/second) returns the value in another unit. Under the hood, the numeric value is in units of whichever unit was assigned the value 1--second in this case. This is best since the input to the function is already in seconds.

Granted, the last line let seconds = rest/second is somewhat redundant since second = 1, but it keeps with the pattern. However, if totalSeconds could be a floating point number, the zeroPad() function doesn't work since the length of the string is already longer than 2.