Kata

This excercise is a more sophisticated version of Simple Events kata.

Your task is to implement an Event constructor function for creating event objects

var event = new Event();

which comply to the following:

• an event object should have .subscribe() and .unsubscribe() methods to add and remove handlers

• .subscribe() and .unsubscribe() should be able take an arbitrary number of arguments and tolerate invalid arguments (not functions, or for unsubscribe, functions which are not subscribed) by simply skipping them

• multiple subscription of the same handler is allowed, and in this case unsubscription removes the last subscription of the same handler

• an event object should have an .emit() method which must invoke all the handlers with the arguments provided

• .emit() should use its own invocation context as handers' invocation context

• the order of handlers invocation must match the order of subscription

• handler functions can subscribe and unsubscribe handlers, but the changes should only apply to the next emit call - the handlers for an ongoing emit call should not be affected

• subscribe, unsubscribe and emit are the only public properties that are allowed on event objects (apart from Object.prototype methods)

Check the test fixture for usage example