JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li class="liclass"></li>
    <li class="liclass"></li>
    <li class="liclass"></li>
    <li class="liclass"></li>
    <li class="liclass"></li>
</ul>

JavaScript

$(function(){
    $('li').each(function(i){
        var $tc = $(this).attr('class')
        $(this).attr('class', $tc+i).text($(this).attr('class')) 
    }) 
})