Convert a number into a Roman Numeral

integerToRoman.js

function integerToRoman(num) {
  let o = {
    M: 1000, CM: 900, D: 500, CD: 400,
    C: 100, XC: 90, L: 50, XL: 40,
    X: 10, IX: 9, V: 5, IV: 4, I: 1
  }
  let result = ''
  Object.keys(o).map(i => {
    while (num >= o[i]) {
      result += i;
      num -= o[i];
    }
  })
  return result
}

/*
3 -> Output: "III"
4 -> Output: "IV"
9 -> Output: "IX"
*/

function romanToInteger (s) {
  let r = 0;
  let i = 0;
  let o = { M: 1000, D: 500, C: 100, L: 50, X: 10, V: 5, I: 1 };
  while (++i < s.length) {
    c = o[s[i]]
    p = o[s[i - 1]]
    r += c <= p ?  c :  c-p*2        
  }  
  return o[s[0]] + r
}