JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-1.12.4.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/js/select2.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/css/select2.min.css">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/select2-bootstrap-theme/0.1.0-beta.6/select2-bootstrap.min.css">
<div class="panel panel-default">
  <div class="panel-body">
    <div class="btn-toolbar">
      <button class="btn btn-default" data-toggle="collapse" data-target="#collapse-select2" aria-expanded="false">Toggle</button>
    </div>
    <div class="margin-top-16">
      <select class="form-control" data-role="select2">
        <option value="1">Option #1</option>
        <option value="2">Option #2</option>
        <option value="3">Option #3</option>
      </select>
    </div>
    <div class="margin-top-16 collapse" id="collapse-select2">
      <select class="form-control" data-role="select2">
        <option value="1">Option #1</option>
        <option value="2">Option #2</option>
        <option value="3">Option #3</option>
      </select>
    </div>
  </div>
</div>

CSS

.margin-top-16 { margin-top: 16px }
.select2 {
  width: 100%!important;
}

JavaScript

(function($) {
    $(document).ready(function() {
        $('select[data-role="select2"]').select2({
            theme: 'bootstrap'
        });
    });
})(jQuery);