fcc_roman_numeral_converter.js

function convertToRoman(num) {

 // create an ES6-map
 const romanNumbers = new Map()
.set(1000, 'M')
.set(900, 'CM')
.set(500, 'D')
.set(400, 'CD')
.set(100, 'C')
.set(90, 'XC')
.set(50, 'L')
.set(40, 'XL')
.set(10, 'X')
.set(9, 'IX')
.set(5, 'V')
.set(4, 'IV')
.set(1, 'I');

let romanNum ='';
// loop over the romanNumbers map and substitute the input number with the roman equivalent
for (const [arabicLetter, romanLetter] of romanNumbers) { // destructuring the key value pairs from the map
  while (num >= arabicLetter) {
      romanNum += romanLetter;
      num -= arabicLetter;
     }
    }
  return romanNum;

}