Handle credential responses with JavaScript functions

Objective: If the default login flow doesn't meet your requirements, you can customize it in several ways. Read the following information for available customization options.

Key Point: You can use customized JavaScript code in conjunction with the HTML API.

Handle credential response

You can set a JavaScript function in the data-callback attribute to handle the returned credential response. See the following code snippet:

<div id="g_id_onload"
     data-client_id="YOUR_GOOGLE_CLIENT_ID"
     data-callback="handleCredentialResponse">
</div>
<script>
  function handleCredentialResponse(response) {
     // decodeJwtResponse() is a custom function defined by you
     // to decode the credential response.
     const responsePayload = decodeJwtResponse(response.credential);

     console.log("ID: " + responsePayload.sub);
     console.log('Full Name: ' + responsePayload.name);
     console.log('Given Name: ' + responsePayload.given_name);
     console.log('Family Name: ' + responsePayload.family_name);
     console.log("Image URL: " + responsePayload.picture);
     console.log("Email: " + responsePayload.email);
  }
</script>

You can validate and decode the JWT credential by using a JWT-decoding library for your language. You should also verify the Google ID token on your server side.

Note: You cannot set both the data-login_uri attribute and the data-callback attribute.