JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="products-slideshow-thumbs">
  <li><a href="#">test1</a></li>
  <li><a href="#">test1</a></li>
  <li><a href="#">test1</a></li>    
</ul>

CSS

.current { color:red; }

JavaScript

$('ul.products-slideshow-thumbs li').click(function() {
  $(this).toggleClass("current");
});