eventyoshi

Allows several event emitters to be listened and emitted through a single one.

npm install eventyoshi
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eventyoshi Build Status

Allows several event emitters to be handled and emitting to a single one.

concept

Usage

var EventEmtter = require('events').EventEmitter
  , EventYoshi = require('eventyoshi')

var ee1 = new EventEmitter();
var ee2 = new EventEmitter();
var yoshi = new EventYoshi()
  .add(ee1)
  .add(ee2)

yoshi.on('foo', function() {
  console.log('foo!');
});
ee1.emit('foo'); // foo!
ee2.emit('foo'); // foo!

Why?

Why would you use this instead of doing something like

ee1.on('foo', listener);
ee2.on('foo', listener);

Well, you could do that, or you could let EventYoshi handle all the logic for you flawlessly and without modifying the underlying child event emitters. EventYoshi can be treated as another EventEmitter. You can pass it around without having to tell whoever you passed it to what emitters you're listening to and which you aren't listening to anymore.

Same goes for events you might listen to or remove later. As you add more event emitters to event yoshi, it will add listeners that you were already listening for to the emitter you added.

var yoshi = new EventYoshi();
yoshi.on('a', function() {
  console.log('a emitted');
});

var ee = new EventEmitter();
yoshi.add(ee);

ee.emit('a'); // a emitted

And as you remove emitters, all listeners that were added through event yoshi are removed too.

yoshi.remove(ee);
ee.emit('a'); // nothing emitted on yoshi

EventYoshi also supports the once method. It supports listening to newListener such that it is emitted only when listeners are added to your EventYoshi instance and not when they are added to child emitters.

API

yoshi.add(emitter)

Adds an event emitter to an event yoshi.

yoshi.remove(emitter)

Remove an event emitter from an event yoshi.

yoshi.proxy(fn)

Proxies all calls from to yoshi[fn] to its children.

yoshi.add(writeStream);
yoshi.proxy('write', 'end');

yoshi.write(data); // this will call writeStream.write() with data
yoshi.end(); // will call writeStream.end()

When the proxy'd functions are called, they return the values returned from called functions in an array. If the array's length is only 1, returns only the first value.

Events

When events are emitted, this.child will contain the child emitter the event came from. Or in case of newListener event, will contain the event yoshi itself.

yoshi.on('event', function() {
  console.log('Event came from: ', this.child);
});

Event: 'newListener'

  • string - Event.
  • Function - Listener.

Emitted when a listener is added to an event yoshi.

Event: 'newChildListener'

  • string - Event.
  • Function - Listener.

Emitted when a listener is added to an event emitter that has been added to, and not removed from, an event yoshi. Does not emit listeners added by EventYoshi.

Install

npm install eventyoshi

Tests

Tests are written with mocha

npm test

License

MIT

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