JSFiddle - React, Tailwind, and code Playground

HTML

<div id="menu">
    <div class="item"><a href="?product=abc">ABC</a></div>
    <div class="item"><a href="?product=XYZ">XYZ</a></div>
    <div class="item"><a href="?product=Test">Test</a></div>
</div>

JavaScript

var s = 'aBC';

$("#menu").find("a").filter(function(){
   return this.href.split('=')[1].toLowerCase() === s.toLowerCase();
}).addClass("selected");