Untitled

<!DOCTYPE html>
<html>
<head>
</head>

<body>

<p>Change the world</p>
<button onclick="tan()">Click me!</button>

</body>

<script>

function tan(){
	document.getElementsByTagName("p")[0].innerText = "hello"; //because get ElementsByTagName will return an array!

}

</script>

</html>