human-readable-duration-format.md

Human readable duration format ^{4 Kyu}

^{LINK TO THE KATA - STRINGS DATE TIME ALGORITHMS}

Description

Your task in order to complete this Kata is to write a function which formats a duration, given as a number of seconds, in a human-friendly way.

The function must accept a non-negative integer. If it is zero, it just returns "now". Otherwise, the duration is expressed as a combination of years, days, hours, minutes and seconds.

It is much easier to understand with an example:

* For seconds = 62, your function should return
    "1 minute and 2 seconds"
* For seconds = 3662, your function should return
    "1 hour, 1 minute and 2 seconds"

For the purpose of this Kata, a year is 365 days and a day is 24 hours.

Note that spaces are important.

Detailed rules

The resulting expression is made of components like 4 seconds, 1 year, etc. In general, a positive integer and one of the valid units of time, separated by a space. The unit of time is used in plural if the integer is greater than 1.

The components are separated by a comma and a space (", "). Except the last component, which is separated by " and ", just like it would be written in English.

A more significant units of time will occur before than a least significant one. Therefore, 1 second and 1 year is not correct, but 1 year and 1 second is.

Different components have different unit of times. So there is not repeated units like in 5 seconds and 1 second.

A component will not appear at all if its value happens to be zero. Hence, 1 minute and 0 seconds is not valid, but it should be just 1 minute.

A unit of time must be used "as much as possible". It means that the function should not return 61 seconds, but 1 minute and 1 second instead. Formally, the duration specified by of a component must not be greater than any valid more significant unit of time.

Solution

const UNITS = [
  {
    name: 'year',
    seconds: 31536000, // 60 * 60 * 24 * 365
  },
  {
    name: 'day',
    seconds: 86400, // 60 * 60 * 24
  },
  {
    name: 'hour',
    seconds: 3600, // 60 * 60
  },
  {
    name: 'minute',
    seconds: 60, // 60 * 1
  },
]

const isPlural = number => (number > 1 ? 's' : '')

const formatDuration = seconds => {
  let secondsLeft = seconds
  let timeArray = []

  if (seconds === 0) {
    return 'now'
  }

  for (let i = 0; i < UNITS.length; i++) {
    if (secondsLeft >= UNITS[i].seconds) {
      const units = Math.trunc(secondsLeft / UNITS[i].seconds)
      secondsLeft -= units * UNITS[i].seconds
      timeArray.push(`${units} ${UNITS[i].name}${isPlural(units)}, `)
    }
  }

  if (secondsLeft > 0) {
    timeArray.push(`${secondsLeft} second${isPlural(secondsLeft)}, `)
  }

  if (timeArray.length >= 2) {
    timeArray[timeArray.length - 2] = timeArray[timeArray.length - 2].replace(
      ', ',
      '',
    )
    timeArray[timeArray.length - 2] += ' and '
  }

  timeArray[timeArray.length - 1] = timeArray[timeArray.length - 1].replace(
    ', ',
    '',
  )

  return timeArray.join('')
}