Archived Repository The code of this repository was written during a Hack Day by a Marmelab developer. It's part of the distributed R&D effort at Marmelab, where each developer spends 2 days a month for learning and experimentation. This code is not intended to be used in production, and is not maintained.

CO-EVENT

Event emitter returning promise and accepting generator.

This eventEmitter allow to use generator as listener. Additionally, The emit method now return a resolve function that if executed return a promise, that resolve when all listener have correctly executed, or get rejected with the error if one of them failed. The promise will also get rejected if one of the listener failed.

The resolveAll method will return a promise that will resolve when all queued event are done. The promise will also fail if one listener triggered an error.

emit will return an object with a resolve method returning a promise that allow to know when the listener triggered by the event has been executed.

Class: CoEvent

An Event emitter implementation inspired from node EventEmitter returning promise and accepting generator.

All CoEvent emit the event 'newListener' when new listeners are added and 'removeListener' when a listener is removed.

emitter.addListener(event, listener)

emitter.on(event, listener)

Adds a listener to the end of the listeners array for the specified event. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of event and listener will result in the listener being added multiple times. The listener can be a function or a generator.

server.on('connection', function (stream) {
  console.log('someone connected!');
});

Returns emitter, so calls can be chained.

emitter.once(event, listener)

Adds a one time listener for the event. This listener is invoked only the next time the event is fired, after which it is removed.

server.once('connection', function (stream) {
  console.log('Ah, we have our first user!');
});

Returns emitter, so calls can be chained.

emitter.removeListener(event, listener)

Removes a listener from the listener array for the specified event. Caution: changes array indices in the listener array behind the listener.

var callback = function(stream) {
  console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);

removeListener will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified event, then removeListener must be called multiple times to remove each instance.

Returns emitter, so calls can be chained.

emitter.removeAllListeners([event])

Removes all listeners, or those of the specified event. It's not a good idea to remove listeners that were added elsewhere in the code, especially when it's on an emitter that you didn't create (e.g. sockets or file streams).

Returns emitter, so calls can be chained.

emitter.setMaxListeners(n)

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default which helps finding memory leaks. Obviously not all Emitters should be limited to 10. This function allows that to be increased. Set to zero for unlimited.

Returns emitter, so calls can be chained.

emitter.getMaxListeners()

Returns the current max listener value for the emitter which is either set by emitter.setMaxListeners(n) or defaults to EventEmitter.defaultMaxListeners.

This can be useful to increment/decrement max listeners to avoid the warning while not being irresponsible and setting a too big number.

emitter.setMaxListeners(emitter.getMaxListeners() + 1);
emitter.once('event', function () {
  // do stuff
  emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));
});

EventEmitter.defaultMaxListeners

emitter.setMaxListeners(n) sets the maximum on a per-instance basis. This class property lets you set it for all EventEmitter instances, current and future, effective immediately. Use with care.

Note that emitter.setMaxListeners(n) still has precedence over EventEmitter.defaultMaxListeners.

emitter.listeners(event)

Returns a copy of the array of listeners for the specified event.

server.on('connection', function (stream) {
  console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection'))); // [ [Function] ]

emitter.emit(event[, arg1][, arg2][, ...])

Calls each of the listeners in order with the supplied arguments.

Returns An object With

• executedListeners: The number of listeners triggered by the event.
• resolve: A method that return a promise which is fulfilled when all listeners triggered by the event have been successfully executed or rejected with the error thrown by the first failing listener.

emitter.resolveAll()

Return a promise that is fulfilled when all event are resolved, or rejected if one of the event throwed an error.

emitter.listenerCount(type)

• type {Value} The type of event

Returns the number of listeners listening to the type of event.

Event: 'newListener'

• event {String} The event name
• listener {Function} The event handler function

This event is emitted after a listener is added.

Event: 'removeListener'

• event {String} The event name
• listener {Function} The event handler function

This event is emitted after a listener is removed. When this event is triggered, the listener has been removed from the array of listeners for the event.

Inheriting from 'CoEvent'

Inheriting from CoEvent is no different from inheriting from any other constructor function. For example:

'use strict';
const util = require('util');
const EventEmitter = require('events').EventEmitter;

function MyEventEmitter() {
  // Initialize necessary properties from `EventEmitter` in this instance
  EventEmitter.call(this);
}

// Inherit functions from `EventEmitter`'s prototype
util.inherits(MyEventEmitter, EventEmitter);