converting-12-hour-time-to-24-hour-time.md

Converting 12-hour time to 24-hour time ^{7 Kyu}

^{LINK TO THE KATA - DATE TIME ALGORITHMS}

Description

Converting a 12-hour time like "8:30 am" or "8:30 pm" to 24-hour time (like "0830" or "2030") sounds easy enough, right? Well, let's see if you can do it!

You will have to define a function, which will be given an hour (always in the range of 1 to 12, inclusive), a minute (always in the range of 0 to 59, inclusive), and a period (either a.m. or p.m.) as input.

Your task is to return a four-digit string that encodes that time in 24-hour time.

Notes

• By convention, noon is 12:00 pm, and midnight is 12:00 am.
• On 12-hours clock, there is no 0 hour, and time just after midnight is denoted as, for example, 12:15 am. On 24-hour clock, this translates to 0015.

Solution

const to24hourtime = (hour, minute, period) => {
  if (period === 'am' && hour === 12) hour = 0
  if (period === 'pm' && hour !== 12) hour += 12

  const hourString = hour < 10 ? `0${hour}` : `${hour}`
  const minuteString = minute < 10 ? `0${minute}` : `${minute}`

  return `${hourString}${minuteString}`
}