JSFiddle - React, Tailwind, and code Playground

HTML

<div data-foo="bar">
</div>
<div id="target">
</div>
<pre id='results'>
</pre>

JavaScript

var str = "";
str += ($('*[data-foo="bar"]').length + " is expected to be 1. (Works.)\n");

$('#target').data('foo', 'baz');
str += ($('*[data-foo="baz"]').length + " is expected to be 1. (Broken.)\n");

$('#results').text(str);