JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>

<html lang="ja">
<head>
	<meta charset="UTF-8">

	<title>sample</title>
	<script>
	   window.onload = function(){
	   document.getElementsByTagname("body")[0].innerHTML = "Hello world";
	   }
	</script>
</head>

<body>
</body>
</html>

JavaScript

console.log(document.getElementsByTagName("body")[0]);