JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/dot-luv/jquery-ui.css">
<div class="Foo Bar">
    Content
</div>

CSS

.main_row { background: #eee; }
.main_row, .row { display: block; }
.row { padding-left: 20px; }

JavaScript

$(function() {
    alert($('.Foo').length);
});