FunctionProject/api/assets/functions/main/calculateAge.js

const errorHandling = require('../../utils/errorHandling')
const moment = require('moment')
const { requiredFields } = require('../../config/errors')

function calculateAge (
  currentDate,
  { birthDateDay, birthDateMonth, birthDateYear }
) {
  const day = currentDate.getDate()
  const month = currentDate.getMonth()
  const currentDateMoment = moment([currentDate.getFullYear(), month, day])
  const birthDateMoment = moment([birthDateYear, birthDateMonth, birthDateDay])

  // Calcule l'âge - Moment.js
  const ageYears = currentDateMoment.diff(birthDateMoment, 'year')
  birthDateMoment.add(ageYears, 'years')
  const ageMonths = currentDateMoment.diff(birthDateMoment, 'months')
  birthDateMoment.add(ageMonths, 'months')
  const ageDays = currentDateMoment.diff(birthDateMoment, 'days')

  const isBirthday = birthDateDay === day && birthDateMonth === month
  return { ageYears, ageMonths, ageDays, isBirthday }
}

/* OUTPUTS */
module.exports = ({ res, next }, argsObject) => {
  const { birthDate } = argsObject

  // S'il n'y a pas les champs obligatoire
  if (!birthDate) {
    return errorHandling(next, requiredFields)
  }

  const birthDateDay = parseInt(birthDate.substring(0, 2))
  const birthDateMonth = parseInt(birthDate.substring(3, 5) - 1)
  const birthDateYear = parseInt(birthDate.substring(6, 10))

  // Si ce n'est pas une date valide
  const currentDate = new Date()
  const birthDateObject = new Date(birthDateYear, birthDateMonth, birthDateDay)
  const result = calculateAge(currentDate, {
    birthDateYear,
    birthDateMonth,
    birthDateDay
  })
  if (currentDate < birthDateObject || isNaN(result.ageYears)) {
    return errorHandling(next, {
      message: 'Veuillez rentré une date valide...',
      statusCode: 400
    })
  }

  let resultHTML
  if (result.isBirthday) {
    resultHTML = `<p>Vous avez ${result.ageYears} ans. Joyeux Anniversaire! 🥳</p>`
  } else {
    resultHTML = `<p>Vous avez ${result.ageYears} ans, ${result.ageMonths} mois et ${result.ageDays} jour(s).</p>`
  }
  return res.status(200).json({ ...result, resultHTML })
}