How to pop up an alert box when the browser's refresh button is clicked?

Question

If the user refreshes the page in question it will add another record to the database, so I want to warn the user through an alert box if they really want to refresh the pag

Answer 1

There are two possible ways forward with this, both quite different.

One way would be to have an event handler bound to onbeforeunload event so that you can detect when the user is browsing away from the current page. If my memory serves me correctly however, onbeforeunload is not consistent across browsers (I don't think Opera responds to it IIRC, but have no way to currently test). Of course, this solution fails if the user turns off JavaScript.

The second and more robust way would be to implement the Post Redirect Get pattern which when used, prevents the data from being posted again when a user refreshes the page.