Solution for https://www.codewars.com/kata/roman-numerals-helper/train/javascript

roman-numerals-helper.txt

var RomanNumerals = {
  toRoman: function(number) {
    var romans = [
      [1000, 'M'],
      [900, 'CM'],
      [500,  'D'],
      [400,  'CD'],
      [100,  'C'],
      [90,   'XC'],
      [50,   'L'],
      [40,   'XL'],
      [10,   'X'],
      [9,    'IX'],
      [5,    'V'],
      [4,    'IV'],
      [1,    'I']
    ],
    
    output = "";
    
    for(var i = 0; i < romans.length; i++) {
      var glyph = romans[i][1],
          limit = Number(romans[i][0]);
      
      while(number >= limit) {
        output += glyph;
        number -= limit;
      }
    }

    return output;
  },
  
  fromRoman: function(roman) {
    var map = {
      IV:4,
      IX:9,
      XL:40,
      XC:90,
      CD:400,
      CM:900,
      I:1,
      V:5,
      X:10,
      L:50,
      C:100,
      D:500,
      M:1000
      },
      
      value = 0;
    
    for (var i = 0; i < roman.length; i++) {
      var two = map[roman[i]+roman[i+1]], 
          one = map[roman[i]];
      
      if (two != null) { 
        value += two; i++; 
      } else if (one != null) {
        value += one;
      }
    }
    
    return value;
  }
}