JSFiddle - React, Tailwind, and code Playground

HTML

<title>eq demo</title>

<body>
  <div></div>
  <div></div>
  <div></div>
 
  <div></div>
  <div></div>
  <div></div>

CSS

div { width:60px; height:60px; margin:10px; float:left;
        border:2px solid blue; }
  .blue { background:blue;

JavaScript

$("body").children().eq(2).addClass("blue");
$("body").children().eq(20).addClass("blue");
console.log($("body").children());
console.log($("body").children("div"));
console.log($("body").children("div").eq(2));
console.log($("body").children("div").eq(20));