roman-numerals-second

//smaller conversions map object, large ugly helper function, too specific conditional logic in main

const conversions = {
  thousandsLetter: 'M', fiveHundredLetter: 'D', hundredsLetter: 'C', fiftyLetter: 'L', 
  tensLetter: 'X', fiveLetter: 'V', onesLetter: 'I'
};

function convert(n, letter, midLetter, nextLetter) {
  let origNum = Number(n);
  if(origNum === 0) { 
    return '';
  } else if(origNum > 0 && origNum < 4) {
    return letter.repeat(origNum);
  } else if(origNum === 4) {
    return letter + midLetter;
  } else if(origNum === 5) {
    return midLetter;
  } else if(origNum > 5 && origNum < 9) {
    return midLetter + letter.repeat(origNum - 5); 
  } else {
    return letter + nextLetter;
  }
}

function convertToRoman(num) {
  const numArray = String(num).split('');
  const len = numArray.length;  
  const ones = convert(numArray[len - 1], conversions.onesLetter, conversions.fiveLetter, conversions.tensLetter);
  let thousands, hundreds, tens;
  let ansArr = [ones];
  
  if(numArray[len - 2]) {
    tens = convert(Number(numArray[len - 2]), conversions.tensLetter, conversions.fiftyLetter, conversions.hundredsLetter);
    ansArr.unshift(tens);
  }
  
  if(numArray[len - 3]) {
    hundreds = convert(Number(numArray[len - 3]), conversions.hundredsLetter, conversions.fiveHundredLetter, conversions.thousandsLetter);
    ansArr.unshift(hundreds);
  }
  
  if(numArray[len - 4]) {
    thousands = conversions.thousandsLetter.repeat(Number(numArray[0]));
    ansArr.unshift(thousands);
  }
  
  return ansArr.join('');
}