Custom Button Text on JavaScript Confirm

Question

Mega has an interesting function running on it which appears to customize the title and button text of a JavaScript confirm() box:

How is this achieved, when every resource I'm finding here and elsewhere is telling me it's impossible?

Thanks!

Answer 1

Per Passerby's suggestion in the question comments, I did some tests, and it turns out that Chromium's onbeforeunload text is customized for a reload as opposed to a navigation or page close. As such, reloading the page caused the event to fire and return the reload confirmation.

Fiddle: http://jsfiddle.net/eXFnR/

Thanks for the insight!