JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/3.1.9-1/crypto-js.js"></script>

JavaScript

console.log('\n---- using a pass phrase as key will result in AES256 ----')
var encrypted = CryptoJS.AES.encrypt("TEST_TEXT", '9021D105A446', {
  mode: CryptoJS.mode.ECB,
  padding: CryptoJS.pad.Pkcs7
});
console.log('iv:', encrypted.iv.toString());
var decrypt = CryptoJS.AES.decrypt(encrypted, '9021D105A446', {
    mode: CryptoJS.mode.ECB,
    padding: CryptoJS.pad.Pkcs7
});
console.log(decrypt.toString(CryptoJS.enc.Utf8));

console.log('ciphertext: ', encrypted.ciphertext.toString());
console.log('encrypted (it is Base64 already): ', encrypted.toString());//already base64
console.log('encrypted decoded from Base64: ', CryptoJS.enc.Base64.parse(encrypted.toString()).toString()); //note that the full crypted string has a whole other part before ciphertext
try{
  var decrypt2 = CryptoJS.AES.decrypt(encrypted.ciphertext.toString(), '9021D105A446', {
      mode: CryptoJS.mode.ECB,
      padding: CryptoJS.pad.Pkcs7
  });
  console.log('ciphertext.toString() not working: ', decrypt2.toString(CryptoJS.enc.Utf8));
}catch(e){
	console.error('using encrypted.ciphertext can also lead to an error - ', e);
}
var decrypt3 = CryptoJS.AES.decrypt(encrypted.toString(), '9021D105A446', {
    mode: CryptoJS.mode.ECB,
    padding: CryptoJS.pad.Pkcs7
});
console.log('encrypted.toString() working: ', decrypt3.toString(CryptoJS.enc.Utf8));

//UPDATE
console.log('\n---- using a key instead of pass phrase ----');
var pass = 'abcdefghijklmnop'; //must be length 16
var key =  CryptoJS.enc.Utf8.parse(pass);
console.log('raw pass (length 16):', pass);
console.log('usable key (16 bytes):', key);
console.log('key is in Hex when using toString:', key.toString());
var encrypted = CryptoJS.AES.encrypt("TEST_TEXT", key, {
  mode: CryptoJS.mode.ECB,
  padding: CryptoJS.pad.Pkcs7,
});
console.log('encrypted: ', encrypted.toString());
console.log('iv: ', encrypted.iv);
var decrypt = CryptoJS.AES.decrypt(encrypted, key, {
    mode: CryptoJS.mode.ECB,
    padding:...