In Gmail when you are in middle of composing a email and attempt to navigate away from the page they pop up a confirm() dialog box The first line of the box is "Reload site?"
However when I use confirm('message') in the popup that is generated the first line of text always contains the text localhost says
From what I have seen the confirm() only has one parameter message
How is Gmail able to customize that text to say Reload site?
Gmail uses window.onbeforeunload which bypasses the security restriction of showing the sites domain and instead replaces it with a context specific header.
window.onbeforeunload = () => 'some message'