JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="product-thumbs-list">
    <li><a href="1-big.jpg" rel="useZoom: 'cdonZoom', smallImage: '1.jpg'">1</a></li>
    <li><a href="2-big.jpg" rel="useZoom: 'cdonZoom', smallImage: '2.jpg'">2</a></li>
</ul>

JavaScript

$("#product-thumbs-list a").each(function(index) {
   var arrTemp = $(this).attr("rel").split("smallImage: ");
   var value = arrTemp[1];
   alert(value);
});