ROT13 in Javascript

rot13.js

function rot13(str) { // LBH QVQ VG!
  var re = new RegExp("[a-z]", "i");
  var min = 'A'.charCodeAt(0);
  var max = 'Z'.charCodeAt(0);
  var factor = 13;
  var result = "";
  str = str.toUpperCase();
  
  for (var i=0; i<str.length; i++) {
    result += (re.test(str[i]) ?
      String.fromCharCode((str.charCodeAt(i) - min + factor) % (max-min+1) + min) : str[i]);
  }
  
  return result;
}

too bad I haven't learned regex yet
thanks nice