JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/3.1.9-1/hmac-sha256.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/3.1.9-1/enc-base64.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/3.1.9-1/crypto-js.min.js"></script>

JavaScript

var userid = 11223;
var orderNumber = "574285869";
var command = "CaptureCallback";
var data = "18493853499";
var amount = 99.75;
var timestamp = 1596706182;
var string = userid+orderNumber+command+data+amount+timestamp;
document.write(string);
document.write('<br/>');
var hash = CryptoJS.HmacSHA256(string, "7kd9sl8s0bsm409rdsk3jn20");
var hashInBase64 = CryptoJS.enc.Base64.stringify(hash);
document.write(hashInBase64);