Bootstrap 4 Loading Spinner in button

$(document).ready(function() {
    $("#btnFetch").click(function() {
      // disable button
      $(this).prop("disabled", true);
      // add spinner to button
      $(this).html(
        `<span class="spinner-border spinner-border-sm" role="status" aria-hidden="true"></span> Loading...`
      );
    });
});

<link rel="stylesheet" type="text/css" href="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css">

<div style="margin:3em;">
  <form class="form-inline" id="topicForm" action="" method="POST">
    <input type="text" id="inputTopic" name="topic" class="form-control mb-2 mr-sm-2" placeholder="Topic of interest" required autofocus/>
    <button type="button" id="btnFetch" class="btn btn-primary mb-2">Submit</button>
  </form>
</div>

<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.6/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/js/bootstrap.min.js"></script>