Beginner Exercism • javascript

Atbash Cipher

Challenge Overview

Create an implementation of the Atbash cipher, an ancient encryption system created in the Middle East.

Source: Exercism javascript/atbash-cipher

💡 View Solution

const alphabet = 'abcdefghijklmnopqrstuvwxyz';
const reverseAlphabet = [...alphabet].reverse().join('');

const transform = (char) => {
  const index = alphabet.indexOf(char.toLowerCase());
  return index === -1 ? char : reverseAlphabet[index];
};

export const encode = (phrase) => {
  const encoded = phrase.toLowerCase().replace(/[^a-z0-9]/g, '').split('').map(transform).join('');
  return (encoded.match(/.{1,5}/g) || []).join(' ');
};

export const decode = (phrase) => {
  return phrase.toLowerCase().replace(/[^a-z0-9]/g, '').split('').map(transform).join('');
};