jQuery event variable scopes and ES6 classes (JSFiddle)

I'm having some issues getting a class method to fire when events are triggered.

Basically, for buttons #1 and #2, you get the alert, but the _selector property is undefined, so obviously the event triggers fine, but it cant see the _selector property..

But for button #3, all thats really changed, is the btnThree.eventHandler(); gets executed from within an anonymous function... But it works just fine.