JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//code.jquery.com/ui/1.11.4/themes/smoothness/jquery-ui.css">
<script src="//code.jquery.com/ui/1.11.4/jquery-ui.js"></script>
<img src="http://www.test.com" class="img-thumbnail" alt="John Smith (jsmith)">

JavaScript

alert($('.img-thumbnail').attr('alt').match(/\(([^)]+)\)/)[1]);