JSFiddle - React, Tailwind, and code Playground

HTML

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

CSS

div {
    background: red;
    width: 10px;
    height: 10px;
    margin: 10px;
}
.blue {
    background: blue;
}

JavaScript

var i = 0;
var a = setInterval(function () {
    if (i >= 10)
        clearInterval(a);
    i++;
    
    $("body").append("<div /><div /><div /><div /><div /><div /><div /><div /><div /><div />");
    
    $(".blue").remove();
    $("div:nth-child(3n)").after("<div class='blue'></div>");
}, 1000);