events

The events module provides base API for emitting events.

This module is not intended to be used directly by programs. Rather, it is intended to be used by other modules that provide APIs to programs.

API Reference

Classes

EventEmitter

The EventEmitter is the base building block for all compositions that would need to broadcast data to multiple consumers.

Please note that EventEmitter does not expose either a method for emitting events or a list of available event listeners as its public API. Obviously both are accessible but from the instance itself through the private API.

Constructors
EventEmitter()

Creates an EventEmitter object.

Methods
on(type, listener)

Registers an event listener that will be called when events of specified type are emitted.

If the listener is already registered for this type, a call to this method has no effect.

If the event listener is being registered while an event is being processed, the event listener is not called during the current emit.

Example:

// worker is instance of EventEmitter
worker.on('message', function (data) {
  console.log('data received: ' + data)
});
type : String

The type of the event.

listener : Function

The listener function that processes the event.

once(type, listener)

Registers an event listener that will only be called once, the next time an event of the specified type is emitted.

If the event listener is registered while an event of the specified type is being emitted, the event listener will not be called during the current emit.

type : String

The type of the event.

listener : Function

The listener function that processes the event.

removeListener(type, listener)

Unregisters an event listener for the specified event type.

If the listener is not registered for this type, a call to this method has no effect.

If an event listener is removed while an event is being processed, it is still triggered by the current emit. After it is removed, the event listener is never invoked again (unless registered again for future processing).

type : String

The type of the event.

listener : Function

The listener function that processes the event.