@momsfriendlydevco/eventer

Yet-another-implementation of the Node standard Event_Emitter library.

This module acts like a drop-in replacement for the standard require("events") library but is promise compatible.

This module only really differs in that it offers a nicer way to extend objects (extend(myObject)) and handles event emission (emit(<event>)) as promises.

Why

This module differs from the standard event emitter library in several ways:

• emit() returns a promise which resolves with the combined Promise.all() result of all subscribers. It also rejects with the first subscriber throw.
• eventer.extend(anObject) is nicer than the rather strange prototype inheritance system that EventEmitter recommends
• Easily chainable
• Ability to hook into the event call sequence via meta:preEmit + meta:postEmit
• Debugging for the standard eventEmitter object is terrible

Debugging

This module uses the debug NPM module for debugging. To enable set the environment variable to DEBUG=eventer.

For example:

DEBUG=eventer node myFile.js

If you want detailed eventer information (like what exact functions are calling queued), set DEBUG=eventer:detail.

API

emit(event)

Emit an event and return a Promise which will only resolve if all the downstream subscribers resolve. The result is that of Promise.all(subscribers) and is thus always an array. If any subscriber throws the rejection is the first subscriber error. Returns the source object. Note: This function will also emit meta:preEmit (as (eventName, ...args)) and meta:postEmit before and after each event.

on(events, callback)

Subscribe to one or more events. The callback is treated as a Promise factory. Returns the source object.

once(, )

Bind to one event binding exactly once. This is effectively the same as subscribing via on() then calling off() to unsubscribing the same function. Returns the source object.

off(, [function])

Remove an event subscription. If a specific function is specified that lone function is removed, otherwise all bindings are reset. Returns the source object.

listenerCount()

Return the number of listeners for a given event.

eventNames()

Return an array of strings representing each registered event.

extend(