JSFiddle - React, Tailwind, and code Playground

HTML

<html> 
    <body> 
        <div class="chapter">
            <section></section>
            <section></section>
        </div>
        <div class="chapter">
            <section></section>
            <section></section>
            <section class="current"></section>
            <section></section>
        </div>
        <div class="chapter">
            <section></section>
            <section></section>
            <section></section>
            <section></section>
        </div>
    </body>
    
</html>

JavaScript

$(document).ready(function(){
   var sections = $('section');
   alert(sections.index()) ;
    
});