Time difference

calculate-time-difference-absolute.js

const time24TupleToMinutes = ([hours, minutes]) => hours * 60 + minutes;

const timeStrToTuple = timeStr => timeStr.split(":").map(Number);

const time12ToTime24Tuple = time12 => {
  const [hours, minutes] = timeStrToTuple(time12.slice(0, -2));

  const amPm = time12.slice(-2);

  return [
    amPm === "am"
      ? hours === 12 ? hours - 12 : hours
      : hours < 12 ? hours + 12 : hours,
    minutes
  ];
};

const dayMinutes = 24 * 60;

const getRelativeMinutesDiff = (minutes0, minutes1) =>
  minutes0 > minutes1
    ? dayMinutes - minutes0 + minutes1
    : minutes1 - minutes0;

const getAbsoluteMinutesDiff = (minutes0, minutes1) => Math.abs(firstTimeMinutes - secondTimeMinutes);

function StringChallenge(str) { 
  const time12s = str.split("-");

  const time24Tuples = time12s.map(time12ToTime24Tuple);

  const [firstTimeMinutes, secondTimeMinutes] = time24Tuples.map(time24TupleToMinutes);

  return getAbsoluteMinutesDiff(firstTimeMinutes, secondTimeMinutes); 
}
   
console.log(StringChallenge("12:30pm-12:00am"));