How To Decrypt Strings with Vigenère Cipher Made Easy Using a Custom Function in JavaScript

Mastering Vigenère Cipher Decryption in JavaScript

JavaScript Challenges: Beginner to Master — Task #51

Create a function that encrypts a string using the Vigenère cipher.

The function should take a plaintext string and a keyword as arguments and return the encrypted ciphertext. The keyword should be repeated as necessary to match the length of the plaintext.

The Solution to Challenge Task #50

Complete Solution of Task #51

// Solution to Challenge 50

const plaintext = "HELLO WORLD";
const keyword = "SECRET";
const ciphertext = vigenereEncrypt(plaintext, keyword);
console.log(ciphertext); // Outputs: XMCKL QBKHU

function vigenereEncrypt(plaintext, keyword) {
    const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    const input = plaintext.toUpperCase();
    const key = keyword.toUpperCase();

    let result = "";
    let keyIndex = 0;

    for (let i = 0; i < input.length; i++) {
        const char = input[i];
        if (alphabet.includes(char)) {
            const charIndex = alphabet.indexOf(char);
            const keyCharIndex = alphabet.indexOf(key[keyIndex % key.length])…