JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
  <li>What is jQuery?</li>
  <li>What is HTML?</li>
  <li>What is CSS</li>
</ul>

JavaScript

var count = $("ul li").length;
$("ul li").each(function(key,val){
   this.innerHTML += " " + (key+1) + "/"+count;
});