A fun test that should help you to think outside the box. For this event emitter you need to use Ecmascript 6 classes. The test requires you to implement two methods: subscribe and emit.
Subscribe is quite intuitive: it just takes the name of an event and then the callback that we want to attach to that particular name. You have also to implement an unsuscribe process inside this method. The Emits function is the one that you used to call the function that you have subscribed too.