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    1.0.2 • Public • Published


    Simple and fast event emitter library. Subscription is based on a unique Token, which can be used to unsubscribe from the topic.

    The Eventer is used in LightningChart® JS charting library.


    npm install --save @arction/eventer


    Online documentation is available at

    Getting started

    import { Eventer } from '@arction/eventer'
    const eventer = new Eventer()
    // new topic is created, handler is added as the first subscriber to the topic
    const token1 = eventer.on('topic1', () => console.log('I am called from topic1'))
    // 'topic1' already exists, so new listener is simply added to existing collection of handlers
    const token2 = eventer.on('topic1', () => console.log('I am also called from topic1'))
    // new collection of handlers is created for the second topic
    // the function is added to it
    eventer.on('topic2', () => console.log('I am called from topic2'))
    // calls two functions which listen to the event
    // outputs:
    //    I am called from topic1
    //    I am also called from topic1
    // calls single functions which listen to the event
    // outputs:
    //    I am called from topic2
    // remove the second listener from the first topic by token
    // calls single functions which listen to the event
    // outputs:
    //    I am called from topic1
    // remove all listeners from all topics
    // nothing happened, since all subscriptions were terminated

    Subscribe to topic

    Subscribing to a topic is easy.

    eventer.on('topic', ()=>{ console.log('Topic handler') })

    Multiple subscriptions to a single topic can exist.

    eventer.on('topic', ()=>{ console.log('Topic handler') })
    eventer.on('topic2', ()=>{ console.log('Topic 2 handler') })
    eventer.on('topic3', ()=>{ console.log('Topic 3 handler') })

    Unsubscribe from topic

    You can unsubscribe from a single topic by using the Token returned by eventer when you subscribed to the topic.

    const token = eventer.on('topic', ()=>{ console.log('Topic handler') })

    You can also unsubscibe all listeners from a topic.


    It is also possible to unsubscribe all topics and all listeners.


    Emiting events

    Events can be emitted for a topic. The emit can contain 0 or more arguments that will be provided to the topic listeners.

    eventer.on('topic2', ( arg1, arg2 ) => console.log( arg1, arg2 ))
    eventer.emit('topic2', 'Hello ', 'World')

    Development instructions

    The project is developed using TypeScript. Build system of the project heavily relies on Node.js. Dependencies are managed with npm, therefore, remember to run npm install before starting of anything else.

    There are several npm scripts, which are used for development process:

    Name Command Description
    build npm run build run build system
    test npm test run tests and watch
    lint npm run lint run static analyzer and watch
    docs npm run docs generate typedoc documentation
    ci:test npm run ci:test run tests once
    ci:lint npm run ci:lint run static analyzer once
    ci:watch npm run ci:watch run CI circle and watch



    npm i @arction/eventer

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