jQuery addClass example

Change class name on click in jQuery

HTML

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.2/css/bootstrap.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.2/js/bootstrap.min.js"></script>
<div class="container mt-3">
  <button onclick="content()" data-toggle="modal" data-target="#my_modal" class="btn btn-primary">Save</button>
</div>

<form action="addPage.php" method="post">
  <div class="modal fade" id="my_modal" tabindex="-1" role="dialog" aria-labelledby="savePageLabel" aria-hidden="true">
    <div class="modal-dialog" role="document">
      <div class="modal-content">
        <div class="modal-header">
          <h5 class="modal-title" id="savePageLabel">Page Details:</h5>
        </div>
      </div>
    </div>
  </div>
</form>

JavaScript

$(window).load(function(){
	$('#my_Modal').modal('show');
});