Edit in JSFiddle

$(function() {

  var $form = $('#form-contact');
  $form.on("submit", function(e) {
    var formUrl = $(this).attr('action');

    // We don't want the page to submit and refresh
    e.preventDefault();

    // POST the request to Formbackend (the formUrl value)
    $.ajax({
      url: formUrl,
      type: 'POST',
      headers: {
        'accept': 'application/json',
      },
      // We serialize the form fields
      data: $form.serialize()
    }).done(function(response) {
      var successElm = $('<div class="bg-green-100 border border-green-200 text-green-500 p-3">');
      successElm.html(`${response.submission_text}, ${response.values.name}!`);

      $form.parent().replaceWith(successElm);
    }).fail(function() {
      // Happens when something goes wrong
    }).always(function() {
      // This always happens
    });

  });
});

<h1 class="text-xl text-gray-800 font-semibold mb-2">
  Simple contact form (with AJAX)
</h1>
<p class="mb-6 text-gray-600 w-2/3 leading-normal">
  This form uses AJAX to submit to FormBackend. It replaces the form container with the submission text set on the form in FormBackend - and it adds
  one of the values submitted with the form. End result is a green box that says: <span class="bg-indigo-100 px-1">Thank you for your submission, NAME!</span>
</p>. Try submitting it and see! :)

<div id="form-container">
  <form accept-charset="UTF-8" action="https://www.formbackend.com/f/2c6c074cd2b9de69" method="POST" id="form-contact">
    <div class="mb-3">
      <label for="name" class="font-bold uppercase text-gray-600 block tracking-wide text-sm mb-1">Name</label>
      <input type="text" id="name" name="name" class="bg-gray-300 rounded p-2 text-gray-600 focus:shadow-outline focus:outline-none" required>
    </div>

    <div class="mb-3">
      <label for="email" class="font-bold uppercase text-gray-600 block tracking-wide text-sm mb-1">Email</label>
      <input type="email" id="email" name="email" class="bg-gray-200 rounded p-2 text-gray-600 focus:outline-none" required>
    </div>

    <div class="mt-4">
      <button type="submit" class="bg-blue-700 text-white px-4 py-2 rounded">Submit</button>
    </div>
  </form>
</div>