<!-- (A) LOAD CRYPTO JS LIBRARY -->
<!-- https://cryptojs.gitbook.io/docs/ -->
<!-- https://cdnjs.com/libraries/crypto-js -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/4.0.0/crypto-js.min.js"></script>
<script>
// (B) ENCRYPT & DECRYPT FUNCTIONS
var crypt = {
  // (B1) THE SECRET KEY
  secret : "CIPHERKEY",
 
  // (B2) ENCRYPT
  encrypt : function (clear) {
    var cipher = CryptoJS.AES.encrypt(clear, crypt.secret);
    cipher = cipher.toString();
    return cipher;
  },
 
  // (B3) DECRYPT
  decrypt : function (cipher) {
    var decipher = CryptoJS.AES.decrypt(cipher, crypt.secret);
    decipher = decipher.toString(CryptoJS.enc.Utf8);
    return decipher;
  }
};
 
// (C) TEST
// (C1) ENCRYPT CLEAR TEXT
var cipher = crypt.encrypt("FOO BAR");
console.log(cipher);
 
// (C2) DECRYPT CIPHER TEXT
var decipher = crypt.decrypt(cipher);
console.log(decipher);
</script>