Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The onabort property of the GlobalEventHandlers mixin is the event handler for processing abort events sent to the window.
While the standard for aborting a document load is defined, HTML issue #3525 suggests that browsers should not currently fire the abort event on a Window that would trigger onabort to be called.
TODO: define what "abort" is. Closing the window via window manager? Stopping the load of the page? By which means and reasons (user, network/server)? At which stages would it fire / be caught? For IE, onabort is only available with <img> tags.