JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/css/bootstrap-combined.min.css">
<script src="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/js/bootstrap.min.js"></script>
<script src="http://silviomoreto.github.io/bootstrap-select/javascripts/bootstrap-select.js"></script>
<link rel="stylesheet" href="http://silviomoreto.github.io/bootstrap-select/stylesheets/bootstrap-select.css">
<!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-select@1.13.14/dist/css/bootstrap-select.min.css">

<!-- Latest compiled and minified JavaScript -->
<script src="https://cdn.jsdelivr.net/npm/bootstrap-select@1.13.14/dist/js/bootstrap-select.min.js"></script>

    <select id="postcodeSelect" class="selectpicker" title="Postcode" data-size="5" data-live-search="true" multiple data-selected-text-format="count" data-count-selected-text="Postcode ({0} items selected)">
    <option>1</option>
    <option>2</option>
    <option>3</option>
</select>

JavaScript

$('.selectpicker').selectpicker();