Javascript convertidor de números romanos

javascript_convert_roman_number.js

const romanSymbols = {
  '1': 'I',
  '2': 'II',
  '3': 'III',
  '4': 'IV',
  '5': 'V',
  '6': 'VI',
  '7': 'VII',
  '8': 'VIII',
  '9': 'IX',
  '10': 'X',
  '20': 'XX',
  '30': 'XXX',
  '40': 'XL',
  '50': 'L',
  '60': 'LX',
  '70': 'LXX',
  '80': 'LXXX',
  '90': 'XC',
  '100': 'C',
  '200': 'CC',
  '300': 'CCC',
  '400': 'CD',
  '500': 'D',
  '600': 'DC',
  '700': 'DCC',
  '800': 'DCCC',
  '900': 'CM',
  '1000': 'M',
  '2000': 'MM',
  '3000': 'MMM'
}

function convertToRoman(num) {
  const strNumber = String(num);
  const splitNumber = strNumber.split("");

  let un;
  let dc;
  let cn;
  let ml;

  for (let index = splitNumber.length-1; index >= 0; index--) {
    const element = splitNumber[index];
    if(!un){
      un = element;
    } else if(!dc){
      dc = element + "0";
    } else if(!cn){
      cn = element + "00";
    } else if(!ml){
      ml = element + "000";
    }
  }

  if(un){
    un = romanSymbols[un];
  }

  if(dc){
    dc = romanSymbols[dc];
  }

  if(cn){
    cn = romanSymbols[cn];
  }

  if(ml){
    ml = romanSymbols[ml];
  }

  let numbersToConvert = [ml, cn, dc, un];

  return numbersToConvert.reduce((romanNumber, toConvert)=> {
    if(toConvert){
      romanNumber += toConvert;
    }
    return romanNumber;
  }, "");
 }
 
 console.log(convertToRoman(36));
 console.log(convertToRoman(1004));
 console.log(convertToRoman(891));
 console.log(convertToRoman(798));