Convert an integer of 9,999 or less to a roman numeral with JS (just a terrible JS interview question that got stuck in my head)

int-to-roman-numeral.js

const convertToRomanNumerals = int => {
  const romanNumerals = ['I', 'V', 'X', 'L', 'C', 'D', 'M']
  const createRomanNumeralRange = (I, V, X) => [
    '',
    I,
    `${I}${I}`,
    `${I}${I}${I}`,
    `${I}${V}`,
    V,
    `${V}${I}`,
    `${V}${I}${I}`,
    `${V}${I}${I}${I}`,
    `${I}${X}`,
  ]

  return Array.from(String(int))
    .reverse()
    .reduce((prevRomanNumerals, numeral, index) => {
      const nextRomanNumeral = createRomanNumeralRange(
        ...romanNumerals.slice(index * 2, index * 2 + 3),
      )[numeral]

      return `${nextRomanNumeral}${prevRomanNumerals}`
    }, '')
}