JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.0.0-alpha.6/css/bootstrap.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.0.0-alpha.6/js/bootstrap.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/css/select2.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/js/select2.js"></script>

<div  id="myModal" tabindex="-1" class="modal fade">
  <div class="modal-dialog" role="document">
    <div class="modal-content">
      <div class="modal-body">
      <select id="mySelect">
      <option>option 1</option>
      <option>option 2</option>
      </select>
      </div>
      <div class="modal-footer">
        <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
        </div>
    </div><!-- /.modal-content -->
  </div><!-- /.modal-dialog -->
</div><!-- /.modal -->

JavaScript

$("#myModal").modal('show');
$("#mySelect").select2({
	//dropdownParent: $('#myModal')
});