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    event-multiplexer

    1.0.1 • Public • Published

    Event Multiplexer

    If you ever had to register or de-register listeners in bulk and resorted to using arrays, sets, maps and dictionaries to achieve it; This library will take that responsibility off your shoulders.

    This is useful for example in a game or user generated graphics application (which was the original motivation behind this library).

    Artwork

    Features:

    • Listen on multiple event emitters
    • Automatic listening to existing listeners after adding to multiplexer
    • Automatic listener removal after removal from multiplexer
    • Multiplexer events

    Installation

    If you're here, you already know.

    npm install --save event-multiplexer
    

    or

    yarn add event-multiplexer
    

    Usage

    The EventMultiplexer is also itself an implementation of EventEmitter hence any calls to on, off, addListener, removeListener

    The new additions are add(...objects) and remove(...objects) for adding and removing emitters from the multiplexer.

    Initialize

    First create the multiplexer.

    // Import the `EventMultiplexer` class
    import { EventMultiplexer } from  'event-multiplexer';
     
    // Initialize a multiplexer instance.
    const  mux  =  new EventMultiplexer();

    Let's make a few test emitters.

    // This is for demo purposes, any emitter or
    // child implementation will work.
    import { EventEmitter } from 'events';
     
    // Our Test objects.
    const  obj_a = new EventEmitter();
    obj_a.name = "Apple";
     
    const  obj_b = new EventEmitter();
    obj_b.name = "Bose";
     
    const  obj_c  =  new EventEmitter();
    obj_c.name = "Cisco";
     
    const  obj_d  =  new EventEmitter();
    obj_d.name  =  "Dell";

    add(...objects) to the MUX

    Complexity:

    • O(n*m) where n = |objects| and m = |distinct events being listened to|

    Add the objects to the mux

    // You can add objects before you add listeners
    mux.add(obj_a);
     
    // This is a listener (lol duh)
    // More on this later.
    mux.on('EVENT', () => {
        console.log("I like trains.");
    });
     
    // ... and add objects after you add listeners.
    mux.add(obj_b);
     
    // ... or add multiple wherever
    mux.add(obj_b, obj_c, obj_d);

    Don't worry about repeating add operations, it will only listen on the object once.

    Listen on the MUX

    Add listeners on the mux and wait!

    mux.on('HELLO', (object, greeting, ...args) => {
        // The first argument to a handler is always the object
        // producing the event.
        console.log(`${object.name} says: ${greeting}`);
    });
     
    // We have added the objects to the mux before.
    obj_d.emit('HELLO', 'Bonjour');
    obj_a.emit('HELLO', 'Salam');
    obj_c.emit('HELLO', 'Namaste');

    The above will produce the output

    Dell says: Bonjour
    Apple says: Salam
    Cisco says: Namaste
    

    remove(...objects) from the MUX

    Complexity:

    • O(n*m) where n = |objects| and m = |distinct events being listened to|
    const  handler  = () => {}
    mux.on('EVENT', handler);
     
    // Remove.
    mux.off('EVENT', handler);

    MUX without the object being passed.

    const mux = new EventMultiplexer(false);
    mux.on('EVENT', (...args) => {});

    The first argument to the constructor configures it to pass (on default true) or alternatively not pass (on false) the object producing the event to the event handlers.

    Events

    The library also exports OBJECT_ADDED and OBJECT_REMOVED symbols. These can be used to listen for object changes on the multiplexer.

    import {
        OBJECT_ADDED,
        OBJECT_REMOVE,
        EventMultiplexer
    } from `event-multiplexer`;
     
    const obj_a = {name: "A"};
    const obj_b = {name: "B"};
     
    const mux = new EventMultiplexer();
     
    mux.on(OBJECT_ADDED, (object) => {
        console.log(`${object.name} added.`);
    });
     
    mux.on(OBJECT_REMOVED, (object) => {
        console.log(`${object.name} removed.`);
    });
     
    mux.add(obj_a, obj_b);
    mux.remove(obj_a);

    will produce

    A added.
    B added.
    A removed.
    

    Requirements

    Any event emitter implementation that had the on(name, listener) and off(name, listener) methods that work similar to node's implementation should work.

    Internally it uses the EventEmitter export from the environment provided events module. That means you will need so setup your packager to provide that module.

    Webpack provides this by default.

    License

    MIT

    Install

    npm i event-multiplexer

    DownloadsWeekly Downloads

    5

    Version

    1.0.1

    License

    MIT

    Unpacked Size

    21.2 kB

    Total Files

    6

    Last publish

    Collaborators

    • omranjamal