CustomEvent could not be extended

[Stav88]

When I extends CustomEvent using babel the prototype is wrongly set to CustomEventPrototype instead of my class so I can't call methods of my class.

Scenario:

• Extends CustomEvent using ES6 syntax:

export default class MyEvent extends CustomEvent {
    test() {return 'ok';}
}

• Construct event and call test() methods:

const evt = new MyEvent();
console.log(Object.getPrototypeOf(evt));
console.log(evt.test());

• Compile using Babel

Results:

[object CustomEventPrototype]
Object doesn't support property or method 'test'

Expected:

no error

[object MyEvent]
ok

Fix

I find a way to fix that by adding the following code at the end of CustomEvent contructor:

Object.setPrototypeOf(evt, Object.getPrototypeOf(this));

[kumarharsh]

Thanks for reporting this. Can you raise a PR for the same after checking what is the behaviour in browsers which do support CustomEvent? I'm on a mobile so can't check it myself right now.

[Stav88]

I have checked the behaviour of actual browsers without polyfill :

• Gecko (Firefox): support CustomEvent constructor and extends
• Bink (Chrome): support CustomEvent constructor and extends
• Webkit (Safari): support CustomEvent constructor but doesn't support correctly extends
• Edge: support CustomEvent constructor but doesn't support correctly extends
• IE: don't support CustomEvent constructor

[kumarharsh]

Thanks. I'll take a look at your commit in some time...