Convert numbers to roman notation

numToRoman.js

function convert(num) {
  var romanSigns = ['I', 'V', 'X', 'L', 'C', 'D', 'M'];
  var numString = num.toString();

  var numToRoman = function(n, sl, sm, sh) { 
    var syms = [];
    syms.push('', sl, sl+sl, sl+sl+sl, sl+sm, sm, sm+sl, sm+sl+sl, sm+sl+sl+sl, sl + sh);
    return syms[n];
  };
  
  return numString.split('').reverse().map(function (v, i) {
      return numToRoman(v, romanSigns[2 * i], romanSigns[2 * i + 1], romanSigns[2 * i + 2]);
  }).reverse().join('');
}