GoogleAppsScript ROT functions

gistfile1.js

var alphabet = 'abcdefghijklmnopqrstuvwxyz';

function rotText(text, n) {
  var newText = "";
  for (var i = 0, j = text.length; i < j; i++) {
    newText += rot(text[i], n);
  }
  return newText;
}

function rot(letter, n) {
  var index = alphabet.indexOf(letter.toLowerCase());
  if (index < 0) return letter;
  var isUpperCase = letter == letter.toUpperCase();
  var newIndex = (index + n) % alphabet.length;
  var newLetter = alphabet[newIndex];
  return (isUpperCase) ? newLetter.toUpperCase() : newLetter;

}

See https://plus.google.com/103231502413952116096/posts/Sppj1TqUsVC for background.