Scrables a string to privatize it

Scrambler.js

function Encode(str) { 
  
  // Rreplace every letter in the string with the letter following it
  // by first getting the charCode number of the letter, adding 1 to it, then 
  // converting this new charCode number to a letter using the fromCharCode function
  // we also check to see if the character is z and if so we simply convert the z to an a
  var codedString = str.replace(/[a-z]/gi, 
      function(char) { 
        return (char === 'z' || char === 'Z') ? 'a' : String.fromCharCode(char.charCodeAt() + 1);
  });

  // Now successfully converted each letter to the letter following it
  // in the alphabet, and all we need to do now is capitalize the vowels
  var encodedMessage = codedString.replace(/a|e|i|o|u/gi, 
       function(vowel) { 
    return vowel.toUpperCase();
  });

  // return the final string
  return encodedMessage;         
}