Simply russian age formater

ageformater.js

const getLastNumbers = number => number % 100

const getLastNumber = number => number % 10

const inRange = (start, end, number) => number >= start && number <= end


const getNumberForm = number => {

  if (inRange(10, 29, getLastNumbers(number))) {
    return `лет`
  }

  switch (getLastNumber(number)) {

    case 1:
      return `год`

    case 2:
    case 3:
    case 4:
      return `года`

    case 0:
    case 5:
    case 6:
    case 7:
    case 8:
    case 9:
      return `лет`

  }

}


const showAge = number => `${number} ${getNumberForm(number)}`

console.log(showAge(1124))