How to get the "Leave site? Changes that you made may not be saved" when trying to close a window with a populated form

Question

I have a form that when filled in, I can exit the window without being given a warning (I'm using Chrome).

How can I ensure I get a warning before exiting? Is there a Django setting for this?

Answer 1

You need to supply a function returning a string to onbeforeunload of the window or the document body in order to trigger the "Leave site" popup.

window.onbeforeunload = () => '';

<a href="http://example.com">Click to trigger</a>

Answer 2

The event is called beforeunload, so you can assign a function to window.onbeforeunload