JSFiddle - React, Tailwind, and code Playground

HTML

<div id="some">
  
</div>

CSS

#some {
  background: red;
  height: 200px;
  width: 200px;
}

JavaScript

let div = document.querySelector('#some').style

window.onload = setInterval(() => {
  div.backgroundColor = div.backgroundColor == 'red' ? 'blue' : 'red'
}, 1000)