Untitled

<!DOCTYPE html>
<html lang="pt-br">
	<head>
		<meta charset="UTF-8" >
		<title>Exer 2</title>
	</head>
	<body>
		<button>Gerar</button>
		<h2></h2>
		<script>
			document.querySelector("button").onclick = gerar;

			function gerar() {
				var r = Math.floor(Math.random() * 50);
				document.querySelector("h2").innerHTML = r;
			}
		</script>
	</body>


</html>