Convert roman to integer

roman.js

const ROMAN = {
  I: 1,
  V: 5,
  X: 10,
  L: 50,
  C: 100,
  D: 500,
  M: 1000
}

const toInt = c => ROMAN[c] || 0;

const convertRoman = string => {
  const str = string.toUpperCase();
  let res = 0;

  if (str.length === 1) return toInt(str);

  for (let i = 0; i < str.length; i++) {
    const curr = toInt(str[i]);
    const next = toInt(str[i + 1]);

    if (curr >= next) { // eg XI
      res += curr; // Add and iterate
    } else { // eg IX
      res += next - curr; // Subtract the first from second
      i++; // Second character is accounted for.
    }
  }

  return res;
}


const cases = ['I', 'M', 'II', 'III', 'IV', 'IX', 'X', 'XI', 'XC'];

console.log(cases.map(c => convertRoman(c)))