index.js

import React from "react"
import ReactDOM from "react-dom"

// https://stackoverflow.com/a/33292942
function timeout(timeoutMs) {
	return new Promise(resolve => setTimeout(resolve, timeoutMs))
}

;(async () => {
	const root = document.getElementById("root")

	ReactDOM.render(
		<div>
			hello, world!
		</div>,
		root,
	)
	await timeout(1e3)
	root.children[0].innerHTML = "lol"
	await timeout(1e3)
	ReactDOM.render(
		<div>
			hello, world! 2
		</div>,
		root,
	)
})()