event-registry

Keeps track of EventEmitter listeners and automatically removes them upon selected events. Useful when you want to avoid EventEmitter memory leaks caused by listeners not being removed.

Usage

const EventRegistry = require('event-registry')
 
const eventRegistry = new EventRegistry()
const emitter = getSomeEventEmitter()
const otherEmitter = getSomeOtherEventEmitter()
 
// Attach a listener using EventEmitter.prototype.on and remember it.
eventRegistry.on(emitter, 'data', someDataListener)
 
// Attach a one-off listener using EventEmitter.prototype.on and remember it.
eventRegistry.once(emitter, 'end', someEndListener)
 
// A single registry can track any number of event emitters.
eventRegistry.on(otherEmitter, 'progress', someProgressListener)
 
// When the 'end' event is emitted, remove all remembered listeners.
// Note that this will also remove the progress listener from otherEmitter.
eventRegistry.fin(emitter, 'end')

API

EventEmitter Proxies

An EventRegistry proxies the following functions to the emitter:

• addListener(emitter, event, listener) AKA on(emitter, event, listener)
• once(emitter, event, listener)
• removeListener(emitter, event, listener)
• removeAllListeners(emitter, [event])

Additionally, it keeps track of every listener passed. When a final event occurs (see below), it will remove all of these listeners.

Final Events

fin(emitter, event)

Marks the given event on the emitter as final. When that event occurs, all listeners will be removed.

unfin(emitter, event)

Undoes a call to fin. Marks the event on the emitter as non-final.

onceFin(emitter, event, listener)

Shorthand for once(emitter, event, listener) followed by fin(emitter, event). Saves you a statement in this common scenario.

clear()

Removes all attached listeners and marks all final events as non-final. Basically what happens when a final event is emitted.

Author

Tim De Pauw

License

MIT