"Not a robot" recaptcha without a <form> but AJAX instead

Question

The traditional way of using "I am not a robot" Recpatcha seems to be with a <form> on client-side:

<form action="post.php" method="POST">
    <div class="g-recaptcha" data-sitekey="6Lc_0f4SAAAAAF9ZA_d7Dxi9qRbPMMNW-tLSvhe6"></div>
    <button type="submit">Sign in</button>
</form>

<script src='https://www.google.com/recaptcha/api.js'></script>

Then some g-recaptcha-response will be sent to server.

---

However, in my code I don't use a <form> but an AJAX call instead:

$('#btn-post').click(function(e) { 
  $.ajax({
    type: "POST",
    url: "post.php",
    data: {
      action: 'post',
      text: $("#text").val(),
      ajaxMode: "true"
    },
    success: function(data) { },
    error: function(data) { } 
  }); } });

How to get the g-recaptcha-response answer with this solution?

Answer 1

I just implemented it without using any form and submit mechanism, respectively. Thus, a pure AJAX solution.

HTML code:

<div id="recaptcha-service" class="g-recaptcha"
 data-callback="recaptchaCallback"
 data-sitekey=""></div>
<script type="text/javascript" src="https://www.google.com/recaptcha/api.js?hl=en"></script>

JavaScript code:

window.recaptchaCallback = undefined;

jQuery(document).ready(function($) {

  window.recaptchaCallback = function recaptchaCallback(response) {
    $.ajax({
      method: "POST",
      url: "http://example.com/service.ajax.php",
      data: { 'g-recaptcha-response': response },
    })
      .done(function(msg) {
        console.log(msg);
      })
      .fail(function(jqXHR, textStatus) {
        console.log(textStatus);
      });
  }

});

The point is using a callback (recaptchaCallback in this case).

You can find a more complete example at https://gist.github.com/martinburger/f9f37770c655c25d5f7b179278815084. That example uses Google's PHP implementation on the server side (https://github.com/google/recaptcha).