使用momentJS计算年龄并获得不同的输出字符串

const pluralize = (str, n) => n > 1 ? `${n} ${str.concat('s')}` : n == 0 ? '' :`${n} ${str}`

const calcAge = (dob) => {
  const age = moment.duration(moment().diff(moment(dob)))
  const ageInYears = Math.floor(age.asYears())
  const ageInMonths = Math.floor(age.asMonths())
  const ageInDays = Math.floor(age.asDays())

  if (age < 0)
    throw 'DOB is in the future!'

  let pluralYears = pluralize('year', ageInYears)
  let pluralDays = pluralize('day', age.days())

  if (ageInYears < 18) {
    if (ageInYears >= 1) {
      return `${pluralYears} ${pluralize('month', age.months())}`
    } else if (ageInYears < 1 && ageInMonths >= 1) {
      return `${pluralize('month', ageInMonths)} ${pluralDays}`
    } else {
      return pluralDays
    }
  } else {
    return pluralYears
  }

}

console.log(calcAge('2000-01-01')) // 18 Years
console.log(calcAge('2011-05-01')) // 7 years 5 months
console.log(calcAge('2015-10-01')) // 3 years 
console.log(calcAge('2017-05-01')) // 1 year 5 months
console.log(calcAge('2018-09-01')) // 1 month 5 days
console.log(calcAge('2018-10-01')) // 6 days
console.log(calcAge('2018-07-07')) // 3 months
console.log(calcAge('2099-12-01')) // Uncaught DOB is in the future!

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