JarCastingEventEmitter3
EventEmitter3 is a high performance EventEmitter. It has been micro-optimized for various of code paths making this, one of, if not the fastest EventEmitter available for Node.js and browsers. The module is API compatible with the EventEmitter that ships by default with Node.js but there are some slight differences:
- Domain support has been removed.
- We do not
throwan error when you emit anerrorevent and nobody is listening. - The
newListenerandremoveListenerevents have been removed as they are useful only in some uncommon use-cases. - The
setMaxListeners,getMaxListeners,prependListenerandprependOnceListenermethods are not available. - Support for custom context for events so there is no need to use
fn.bind. - The
removeListenermethod removes all matching listeners, not only the first.
It's a drop in replacement for existing EventEmitters, but just faster. Free performance, who wouldn't want that? The EventEmitter is written in EcmaScript 3 so it will work in the oldest browsers and node versions that you need to support.
Installation
$ npm install --save eventemitter3
CDN
Recommended CDN:
https://unpkg.com/eventemitter3@latest/umd/eventemitter3.min.js
Usage
After installation the only thing you need to do is require the module:
var EventEmitter = require('eventemitter3');
And you're ready to create your own EventEmitter instances. For the API documentation, please follow the official Node.js documentation:
http://nodejs.org/api/events.html
Contextual emits
We've upgraded the API of the EventEmitter.on, EventEmitter.once and EventEmitter.removeListener to accept an extra argument which is the context or this value that should be set for the emitted events. This means you no longer have the overhead of an event that required fn.bind in order to get a custom this value.
var EE = new EventEmitter()
, context = { foo: 'bar' };
function emitted() {
console.log(this === context); // true
}
EE.once('event-name', emitted, context);
EE.on('another-event', emitted, context);
EE.removeListener('another-event', emitted, context);
Tests and benchmarks
This module is well tested. You can run:
npm testto run the tests under Node.js.npm run test-browserto run the tests in real browsers via Sauce Labs.
We also have a set of benchmarks to compare EventEmitter3 with some available alternatives. To run the benchmarks run npm run benchmark.
Tests and benchmarks are not included in the npm package. If you want to play with them you have to clone the GitHub repository. Note that you will have to run an additional npm i in the benchmarks folder before npm run benchmark.
