Recursive Caesar Cipher

recursive-caesar-cipher.js

const recursiveCaesarCipher = (shift, text) => {
    const inner = (shift, [ letter, ...rest]) =>  {
        const index = alphabet.indexOf(letter);
        const newIndex = (index + shift) % alphabet.length;
        return [ 
            index >= 0 ? alphabet[newIndex] : letter, 
            ...rest.length ? inner(shift, rest) : [] 
        ]
    }

    return inner(shift, [ ...text ]).join('');
}