mr-EventEmitter

Provides ability to subscribe and emit events. This event emitter is tailored for real-time applications so is designed with performance and memory efficiency in mind.
Also it has two build targets: ES5 (ECMA2009) and ES8+ (modern JS), to maximize browser support without sacrificing benefits of modern JS for majority of users.

:rocket: Install

Node.js

Install:

npm install mr-eventemitter

In code:

const EventEmitter = require('mr-eventemitter');

Browser

<script type='module' src='mr-eventemitter.min.js'></script>
<script nomodule src='mr-eventemitter.es5.min.js'></script>

Use built files from a dist directory for the browser. It will load ES8+ version if it is supported (~94%), otherwise it will load ES5 (ECMA2009) version that supports pretty much every platform.

CDN (jsDelivr)

You can use a public CDN for the library:

ES8+ module: https://cdn.jsdelivr.net/npm/[email protected]/dist/mr-eventemitter.min.js
ES5 version: https://cdn.jsdelivr.net/npm/[email protected]/dist/mr-eventemitter.es5.min.js

Example

let obj = new EventEmitter();

obj.on('event', (a) => {
    console.log('event', a);
});

obj.emit('event', 42);

:scroll: API Documentation

Usage

Creating:

Creating event emitter directly:

let obj = new EventEmitter();

With class:

class World extends EventEmitter {
    contrunctor() {
        super();
    }
}

With prototype:

function World() {
    EventEmitter.call(this);
}
World.prototype = Object.create(EventEmitter.prototype);
World.prototype.constructor = World;

Emitting:

obj.emit('event', 42);

Or with many arguments:

obj.emit('event', 4, 8, 16, 32);

Subscribing:

obj.on('event', function(value) {
    console.log('event', value);
});

It is possible to pass to an event many arguments:

obj.on('event', function(a, b, c, d) {
    console.log('event', a, b, c, d);
});

For single life event use once:

obj.once('event', function(value) {
    console.log('event', value);
});

Sometimes providing scope for a callback function is usefull:

class Place {
    constructor() {
        this.name = 'Home';

        world.on('event', function() {
            // this - will be this `Place` instead of `world`
            console.log('event', this.name); // hello Home
        }, this); // - notice `this`
    }
}

Removing events:

To remove event handler, you can use off method on EventEmitter:

obj.off('event', fn);

To remove all events by name:

obj.off('event');

Remove a group of events, that match a regular expression:

obj.off(/input:\w+/);

obj.emit('init');
obj.emit('input:start');    // ignored
obj.emit('input:end');      // ignored

To remove all events:

obj.off();

And for easier management, on and once methods return EventHandler, which then can be used for removing events:

let evt = obj.on('event', (value) => {
    console.log('event', value);
});

evt.off();

Building

Builds a single file into two ES5 and ES8+ versions using Babel and Terser.
Source file: src/index.js
Built versions ES5 (dist/mr-eventemitter.es5.min.js) and ES8+ (dist/mr-eventemitter.min.js):

npm install
npm run build