JSFiddle - React, Tailwind, and code Playground

HTML

<p>Bootstrap Select // brynner.net</p>
<div class="input-group-btn select" id="select1">
    <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown" aria-expanded="false"><span class="selected">One</span> <span class="caret"></span></button>
    <ul class="dropdown-menu option" role="menu">
    <li id="1"><a href="#">One</a></li>
    <li id="2"><a href="#">Two</a></li>
    </ul>
</div>

CSS

body {margin:20px;}

.select button {width:100%; text-align:left;}
.select .caret {position:absolute; right:10px; margin-top:10px;}
.select:last-child>.btn {border-top-left-radius:5px; border-bottom-left-radius:5px;}
.selected {padding-right:10px;}
.option {width:100%;}