Execute js function before closing browser tab?

Question

JavaScript

Such a situation is that you need to perform the function of displaying a pop-up window (the function itself works) before the user, being on the site, wants to leave it, i.e. closes the browser tab. How to catch this action? Are there similar solutions that worked in most popular browsers?
If there is no such solution, then tell me an option in solving this problem?

Answer 1

Watson, elementary!

Answer 2

There is an onload window loading event and an onunload event that is called before the browser closes.