JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-1.12.4.min.js"></script>
<link rel="stylesheet" href="https://bootswatch.com/3/darkly/bootstrap.min.css">
<script src="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/select2@4.0.13/dist/css/select2.min.css">
<link rel="stylesheet" href="https://cdnjhttps//cdnjs.cloudflare.com/ajax/libs/select2-bootstrap-theme/0.1.0-beta.10/select2-bootstrap.min.csss.cloudflare.com/ajax/libs/select2-bootstrap-theme/0.1.0-beta.10/select2-bootstrap.min.css">
<script src="https://cdn.jsdelivr.net/npm/select2@4.0.13/dist/js/select2.min.js"></script>
<select class="select2">
  <option value="1">test 1</option>
  <option value="2">test 2</option>
  <option value="3">test 3</option>
  <option value="4">test 4</option>
  <option value="5">test 5</option>
</select>

CSS

.select2 {
  width: 100%;
}

JavaScript

$('.select2').select2({
  theme: 'bootstrap'
});