Bottone con Alert in FORM

' Show a push button:

<!DOCTYPE html>
<html>
<body>

<h1>Show a push button:</h1>

<p>The button below activates a JavaScript when it is clicked.</p>

<form>
<input type="button" value="Click me" onclick="msg()">
</form>

<script>
function msg() {
alert("Hello world!");
}
</script>

</body>
</html>