I have twitted already that it sucks as it is, and while it's really trivial to implement the same for any browser, I believe many mistakes have been made about the API. Here the list:
- on() is a shortcut for addListener but there is no off() as removeListener's shortcut (inconsistent)
- add/removeListener is not DOM friendly, we cannot reuse an EventEmitter in the browser without double checking if those methods exist
- removeAllListeners() accepts no arguments and cleans up the whole emitter but there is no way to retrieve all listeners via listeners() passing no arguments (again, inconsistent)
- there's no possibility to use handleEvent property, as already defined in the EventListener, once again objects are not reusable between client and server
- no duplicated checks for both addListener and removeListener, this is totally inconsistent against DOM EventTarget plus I found it kinda hilarious since there is also a max number of listeners allowed defined via setMaxListeners method ... if we add same listener twice, it's fired twice ... a non-sense for those coming from the web. We also need to removeListener twice or more 'cause we have no idea if same listeners has been added by mistake twice so ... it's just screwed up, removing a specific listener may be not enough and there is no easy way to check if the listener has been removed or not
- there is no interface to define events plus the single argument is not a DOM Event like, not even an object with data property and at least a type that points to the event name ... once again, not possible to reuse anything on DOM world
I have personally created wru which runs in all browsers and many server side JS environments but what I would like to avoid is to write twice any sort of test because of weirdly implemented APIs.
If it's about shortcutting, as example, on() and off() are more than welcome but why on earth the long version should be addListener rather than addEventListener?
Why events passed as objects since ever in client JS should be passed as string with optional extra data as second argument?
Where are defaults control over events fired across more listeners?
Why on earth handleEvent is not supported and a listener can be only a function which most likely will require a bind to something else?
Why is it possible to erase all listeners without even knowing "who set them where" but it's not possible to retrieve all of them so that at least we could act accordingly with the event name following some rule rather than "just remove them all" ?
I hope somebody will agree with me, considering flakey points I have already described and changing or improving ASAP this EventEmitter API ... it would be sooooooo coooool to be aligned in both worlds for at least the most used pattern/procedure ever in JS world, don't you say? Thanks for your attention.