The simplest (and smallest) Event Emitter implementation

emitta is an 45 lines of code EventEmitter. emitta is smaller and faster than its competitors, simply because its API is ridiculously simple. And it's also cross-browser. Include this <1ko (287b gzipped) library to your project to attach and emit events!

Why emitta ?

We have all seen and used great EventEmitters libraries. And most of the time, we use them to do only two things: attaching and emitting events. Nothing else. But these libraries also include other advanced usages of emitters that we, most of the time, don't need.

emitta aims to solve the simple need of emitting and attaching events, without anything else.

Why the name emitta?

I didn't want to create yet another EventEmitterX, X being the 1000th version. So I picked up a new name, based on the english pronunciation of emitter in Japanese.

Installation

With Yarn

$ yarn add emitta

With npm

$ npm install emitta --save

Usage

var EventEmitter = require('emitta')

// Create a new instance
var emitta = new EventEmitter()

// Attach event
emitta.on('myEvent', function() {
  console.log('Hello world!')
})

// Emit event
emitta.emit('myEvent') // Hello world!

// Delete event
emitta.removeListener('myEvent')

// Delete all events
emitta.removeAllListeners()

// That's it! Simple right?

API

.on(eventName, callback)

.on is used to attach an event to a callback

If eventName or callback are not defined, nothing will be attached. callback must be a function. Otherwise, an error is thrown.

⚠️ For simplicity reasons, if you attach the same event multiple times, only the last callback will be stored.

.emit(eventName)

.emit is used to call the function associated with the eventName event.

eventName must have already been attached to a callback.

.removeListener(eventName)

.removeListener removes the selected event if it exists.

.removeAllListeners()

.removeAllListeners flushes all the events from the EventEmitter

Benchmarks

⚠️ For now, benchmarks have been taken from the great EventEmitter3. Homemade benchmarks are coming!

emitta was benchmarked against its competitors on the three things an EventEmitter should do: attaching, emitting and removing events.

Benchmarking attaching/removing events with .on and .removeListener

Run the benchmark:

node benchmarks/eventemitter3-benchmarks/listening.js

Results:

EventEmitter1 x 4,006,233 ops/sec ±7.24% (67 runs sampled)
EventEmitter2 x 1,136,366 ops/sec ±3.54% (71 runs sampled)
[email protected] x 15,470,152 ops/sec ±9.77% (66 runs sampled)
Drip x 27,336,329 ops/sec ±3.98% (71 runs sampled)
fastemitter x 8,953,721 ops/sec ±3.68% (74 runs sampled)
event-emitter x 1,328,110 ops/sec ±4.37% (68 runs sampled)
contra/emitter x 5,534,475 ops/sec ±3.39% (79 runs sampled)
dcamilleri/emitta x 47,981,718 ops/sec ±5.21% (77 runs sampled)
Fastest is dcamilleri/emitta

Benchmarking emitting events with .emit

Run the benchmark:

node benchmarks/eventemitter3-benchmarks/emit.js

Results:

EventEmitter1 x 47,965,828 ops/sec ±1.47% (78 runs sampled)
EventEmitter2 x 24,178,318 ops/sec ±12.50% (67 runs sampled)
[email protected] x 33,571,858 ops/sec ±3.31% (70 runs sampled)
Drip x 27,198,636 ops/sec ±2.39% (76 runs sampled)
fastemitter x 16,157,850 ops/sec ±4.33% (72 runs sampled)
event-emitter x 9,982,259 ops/sec ±4.53% (69 runs sampled)
contra/emitter x 443,390 ops/sec ±4.48% (73 runs sampled)
dcamilleri/emitta x 73,502,204 ops/sec ±3.07% (73 runs sampled)
Fastest is dcamilleri/emitta

Bonus: creating an instance

Run the benchmark:

node benchmarks/eventemitter3-benchmarks/init.js

Results:

EventEmitter1 x 35,884,967 ops/sec ±2.50% (83 runs sampled)
EventEmitter2 x 31,389,033 ops/sec ±1.56% (78 runs sampled)
[email protected] x 89,695,581 ops/sec ±4.31% (70 runs sampled)
Drip x 99,789,081 ops/sec ±2.83% (78 runs sampled)
fastemitter x 12,505,656 ops/sec ±1.17% (87 runs sampled)
event-emitter x 374,599 ops/sec ±0.95% (81 runs sampled)
contra/emitter x 799,779 ops/sec ±5.48% (53 runs sampled)
dcamilleri/emitta x 97,672,988 ops/sec ±3.25% (78 runs sampled)
Fastest is Drip,dcamilleri/emitta

Run tests

$ yarn && yarn test

License

MIT © Dorian Camilleri