JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li class="id1">item 1</li>
    <li class="id2">item 1</li>
    <li class="id3">item 1</li>
    <li class="id4">item 1</li>
<ul>
    
<ul>
    <li class="test1">item 1</li>
    <li class="test2">item 1</li>
    <li class="test3">item 1</li>
    <li class="test4">item 1</li>    
</ul>
<h1>scd</h1>

JavaScript

$.fn.testFn = function(){

		$('h1').text($(this).attr('class'));
    this.each(function(){
        var className = $(this).attr('class');
        $(this).html(className);
    });    
};
              
$('li').testFn();