vigenere with functions p5

vigenere_refacored.ts

function vigenere_cipher(alphabet:string, key:string): (str:string, equation:cipher_equation) => string {
  const L = alphabet.length;

  return function(str, equation) { // this is the previous 'vigenere_cipher' function but as an anonymous function. 
    const repeated_key = repeat_key(str.length, key);
    return str
      .split("")
      .map((C, i) => {
        const Ci = alphabet.indexOf(C);
        const K = repeated_key[i];
        const Ki = alphabet.indexOf(K);

        if(Ci === -1) return C;

        const Ri = equation(Ci, Ki, L);

        return alphabet[Ri];
      })
      .join("");
  };
}