Convert a number to Roman Numerals

toRomanNumerals.js

function solution(roman){
  let RomanNum = {
    10:    { 1: 'I', 5: 'V'},
    100:   { 1: 'X', 5: 'L'},
    1000:  { 1: 'C', 5: 'D'},
    10000: { 1: 'M'}
  };
  let result = '';
  for (let d in RomanNum) {
    let tmp = '';
    let n = roman % d;
    roman -= n;
    console.log(n);
    n /= (d/10);
    if (n === 9) {
      tmp = RomanNum[d][1]+RomanNum[d*10][1];
      n = 0;
    }
    if (n >= 5) {
      tmp = RomanNum[d][5];
      n -= 5;
    }
    if (n === 4) {
      tmp = RomanNum[d][1] + RomanNum[d][5];
      n = 0;
    }
    while(n-- > 0) {
      tmp += RomanNum[d][1];
    }
    result = tmp + result;
  }
  return result;
}