romanNumerals in js

toRoman.js

const toRoman = (numeral) =>
  new Array(numeral + 1)
    .join('I')
    .replaceAll('IIIII', 'V')
    .replaceAll('VV', 'X')
    .replaceAll('XXXXX', 'L')
    .replaceAll('LL', 'C')
    .replaceAll('CCCCC', 'D')
    .replaceAll('DD', 'M')
    .replaceAll('IIII', 'IV')
    .replaceAll('VIV', 'IX')
    .replaceAll('XXXX', 'XL')
    .replaceAll('LXL', 'XC')
    .replaceAll('CCCC', 'CD')
    .replaceAll('DCD', 'CM');

toRoman(2020);
toRoman(1999);