JSFiddle - React, Tailwind, and code Playground

HTML

<div id="myForm">
  <form method="post" id="contact-form" action="placeholder.php">
    <div class="row uniform">
      <div class="6u 12u$(medium)">
        <input type="text" name="fullname" id="fullname" value="" placeholder="Enter your full name" required />
      </div>
      <div class="6u 12u$(medium)">
        <input type="email" name="email" id="email" value="" placeholder="enter your email address" required />
      </div>
      <div class="6u 12u$(medium)">
        <textarea name="comment" id="comment" value="" placeholder="Enter your message"></textarea>
      </div>
      <div class="6u 12u$">
        <ul class="actions">
          <li>
            <input type="submit" value="Submit" class="special" />
          </li>
        </ul>
      </div>

    </div>
  </form>
</div>

JavaScript

$("#contact-form").submit(function(e) {
  e.preventDefault();
  $.post($(this).attr('action'), $(this).serialize());
  $("#myForm").html("thank you for submitting your details.");
});