183629 2018-03-14 05:56:38 -0700 Allow extending of event objects 2020-04-17 15:03:38 -0700 1 1 1 Unclassified WebKit DOM Safari Technology Preview Unspecified Unspecified RESOLVED CONFIGURATION CHANGED https://bugs.webkit.org/show_bug.cgi?id=174313 P2 Normal --- 1 jaffathecake webkit-unassigned ashvayka oldest_to_newest 1406370 0 jaffathecake 2018-03-14 05:56:38 -0700 class Foo extends Event {} console.log(new Foo('bar').constructor); Chrome & Firefox say Foo, Edge & Safari say Event. The Chrome/Firefox behaviour is preferable, as it allows you to create custom event objects, which is especially useful when developing custom elements. 1406704 1 jaffathecake 2018-03-15 10:29:42 -0700 Tests: http://w3c-test.org/dom/events/Event-subclasses-constructors.html 1503354 2 lforschler 2019-02-06 09:19:17 -0800 Mass move bugs into the DOM component. 1642858 3 ashvayka 2020-04-17 15:03:38 -0700 (In reply to Jake Archibald from comment #1) > Tests: http://w3c-test.org/dom/events/Event-subclasses-constructors.html As of r256716, extending Event (as well as other DOM constructors) works as expected. Provided test file is 100% passing.