Algorithm I did for freeCodeCamp

converttoroman.js

function convertToRoman(num) {
  function addSymbols(carrier, val, symbol) {
    var returnString = carrier[0];
    var startingValue = carrier[1];
    for ( ; startingValue >= val; startingValue -= val) {
      returnString += symbol;
    }
    return [returnString, startingValue];
  }
  
  var rv = "";
  var carrier = [rv, num];
  var subs = [[1000, "M"],
              [900, "CM"],
              [500, "D"],
              [100, "C"],
              [90, "XC"],
              [50, "L"],
              [40, "XL"],
              [10, "X"],
              [9, "IX"],
              [5, "V"],
              [4, "IV"],
              [1, "I"]];
  for (var i = 0; i < subs.length; i += 1) {
    var sub = subs[i];
    carrier = addSymbols(carrier, sub[0], sub[1]);
  }
  rv = carrier[0];
  return rv;
}