Prompt User before browser close?

Question

We have an administrative portal that our teachers constantly forget to download their latest PDF instructions before logging out and/or closing the browser window. I have l

Answer 1

You cannot alert or things like that in onbeforeunload, you cannot simply return false to make the user not leave the page, as with other events like onclick. This would allow a site to make it impossible to leave it.

You can however just return a string, the browser then shows a confirm dialog including your string asking the user whether they really want to leave.