JSFiddle - React, Tailwind, and code Playground

HTML

<nav id="menu">
<li>
   <ul>
      <li><a href="/root/page1.html">page1</a></li>
      <li>
          <ul>
               <li><a href="/root/page2.html">page2</a></li>
               <li><a href="/root/page3.html">page3</a></li>
              <li><a href="https://fiddle.jshell.net">page3</a></li>
          </ul>
      </li>
   </ul>
</ul>
</nav>

CSS

.current-page {border: 1px solid red;}

JavaScript

$('#menu a').each(function(){
    var href = $(this).attr('href');
        
    if ( window.location.href.indexOf(href) >= 0 ){
        $(this).parent('li').addClass('current-page');
    }
});