Can we access the URL of next request of browser in prevailing HTML page 's unload function

As Html code resides until new url request's response doesn't come .Then Browser calls BeforeUnload and Unload function.

This means anywhere in the browser, the url is residing which has been hit for unloading the current one. So is there any way we can get that (new) URL in the Unload function?

Actually My scenario is that I want pop up to be opened for providing the other options when user has just hit another URL which doesn't resemble to our domain , showing that he want to go out from our site.