const RomanNumber = require('roman-number'); // npm i -S caub/roman-number
const num1 = RomanNumber('XX');
const num2 = RomanNumber(40);
console.log(num1.toInt(), num2.toString()) // 20 'XL'- node.js >= 6
- browser (Chrome, Firefox, Edge, IE11, Safari, ..)
(requires String.prototype.repeat, that can be shimmed)
