How can I process HTML form validation before reCAPTCHA's validation?

I integrated the new hidden reCAPTCHA (v2) framework which by default verifies the user with the click event of the submit button. But this event is triggered before the built-in HTML form validation. I am looking for a way to make it in the expected order: form validation first, reCAPTCHA after.

You have to do it programmatically thanks to a new v2 grecaptcha method: grecaptcha.execute() so that recaptcha doesn't replace the button's default click event which was preventing the default HTML5 form validation.

The event path is:

1. Submit button click event: browser built-in form validation
2. Form submit event: call grecaptcha.execute()
3. reCAPTCHA callback: submit the form

$('#form-contact').submit(function (event) {
    event.preventDefault();
    grecaptcha.reset();
    grecaptcha.execute();
  });

function formSubmit(response) {
  // submit the form which now includes a g-recaptcha-response input
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://www.google.com/recaptcha/api.js"></script>
<form action="?">
  <div class="g-recaptcha" 
       data-sitekey="your-key"
       data-size="invisible"
       data-callback="formSubmit">
  </div>
  <button type="submit">Submit</button>
</form>