In many cases we set an event listener that is removes itself on a first call. I think it will be extremely useful to implement following API: eventEmitter.once('EventType', listener). Also similar thing have recently been added to [nodejs](http://nodejs.org/docs/v0.4.1/api/events.html#emitter.once). As a matter of fact all other major frameworks also provide APIs to do similar thing. In addition I would also propose to implement following low lever module 'api-utils/dom/events' (as this seems to be very useful with regular dom events): require('dom/events').on(element, 'load', onLoad, [capture=false]) require('dom/events').removeListener(element, 'load', onLoad, [capture=false]) require('dom/events').once(element, 'load', onLoadOnly, [capture=false])
Comment on attachment 515173 [details] Pointer to pull request Just a few minor issues, as noted in the pull request.