const rc4 = require('rc4-crypt');

// Initialize encrypt/decrypt
// The keys need to match
let encrypt = rc4("ENCRYPTION KEY"),
    decrypt = rc4("ENCRYPTION KEY");

// The data we're about to encrypt
let plainData = "Hello World";

// Actually encrypt the data
let ciphertext = encrypt(plainData);

// Let's decrypt it again
let decrypted = decrypt(ciphertext);

// Show the result
console.log(decrypted);