How to Execute a JavaScript when the page is about to be unloaded

Close this window, press F5 or click on the link below to invoke the onbeforeunload event.

index.html

Example: HTML

<!DOCTYPE html>
<html>
<body onbeforeunload="return myFunction()">

<p>Close this window, press F5 or click on the link below to invoke the onbeforeunload event.</p>

<a href="https://horje.com">Click here to go to horje.com</a>
  
<script>
function myFunction() {
  return "Write something clever here...";
}
</script>

</body>
</html>

Output should be:

Type:	html
Category:	Web Tutorial
Sub Category:	HTML Attribute
Uploaded by:	Admin