confirmScript.html

<html>
<head>
<script src="https://s3.amazonaws.com/stitch-sdks/js/bundles/4.0.0/stitch.js"></script>
<script>
const {
    Stitch,
    UserPasswordAuthProviderClient
  } = stitch;
  const APP_ID = "YOUR APP_ID FROM MONGODB STITCH";
  const stitchClient = Stitch.initializeDefaultAppClient(APP_ID);

  const emailPasswordClient = stitchClient.auth
    .getProviderClient(UserPasswordAuthProviderClient.factory, "userpass");

  const params = new URLSearchParams(window.location.search);
  const token = params.get('token');
  const tokenId = params.get('tokenId');

  emailPasswordClient
    .confirmUser(token, tokenId)
    .then(() => displayResult('success'))
    .catch(err => displayResult('error', err))

  function displayResult(result, err) {
    const message = document.getElementById("message");
    if (result === "success") {
      message.innerText = "Your E-mail address has been verified.\n\n You may close this page. Thank you.";
    }
    else if (result === "error") {
      message.innerText = "Unable to register this user. Please try again to register." + err;
    }
  }
</script>
<title>Airved: E-mail Confirmation</title>
</head>
<body>
<div id="message"></div>
</body>
</html>