getDaysDiffBetweenDates

Calculates the difference (in days) between two dates.

• Subtract the two Date objects and divide by the number of milliseconds in a day to get the difference (in days) between them.

const getDaysDiffBetweenDates = (dateInitial, dateFinal) =>
  (dateFinal - dateInitial) / (1000 * 3600 * 24);

getDaysDiffBetweenDates(new Date('2017-12-13'), new Date('2017-12-22')); // 9