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    1.2.1 • Public • Published


    Typed emitter providing fully typed methods of the base EventEmitter class


    To install run npm i @jpbberry/typed-emitter


    To use the typed-emitter, you can do so like

    import { EventEmitter } from '@jpbberry/typed-emitter'
    // a type
    interface MyInterface {
      hello: boolean
    // a class that you want to have typed emitters for
    class MyClass extends EventEmitter<{ hello: MyInterface }> { // generic type has the map of events
      // this will then make all the methods have proper typings for the hello event and it's type
      run () {
        this.emit('hello', /* Will be typed as MyInterface */ { hello: true })
        // this will error for example
        this.emit('hello', { hello: 'world!' })
    const my = new MyClass()
    my.on('hello', (data) => { // will be typed as MyInterface
      data.hello // typed as boolean

    Adding multiple arguments

    You can add multiple arguments by defining the property of the event to be an array, this will be spread as properties for the listener function etc.

    For example

    class MyClass extends EventEmitter<{ hello: [boolean, string] }> {
      run () {
        this.emit('hello', true, 'world!') // now the passed data will boolean, string
    const my = new MyClass()
    my.on('hello', (one, two) => {
      one // boolean
      two // string

    Defining an array as something passed to the event just has to be a nested array like { hello: [string[]] }


    As this simply amazing new TypeScript feature begins to gain traction, this library now has support for decorators

    Our decorators are @Event and @Once

    You use these by simply defining them in an extending EventEmitter class and passing your event name to them like @Event('message')

    Here's an example

    import { EventEmitter, Event, Once } from '@jpbberry/typed-emitter'
    class MyClass extends EventEmitter<{ MESSAGE: string }> {
      // You can now simply just use the event decorator above any method you want ran on that event
      @Event('MESSAGE') // Listening to the event MESSAGE
      receivedMessage (message: string) { // the name of the method does NOT matter at all
        console.log(message) // logs the paramater!
    const my = new MyClass()
    my.emit('MESSAGE', 'Hello world!') // logs "Hello world!"

    Note you must enable experimentalDecorators in your tsconfig for these to work


    This library also comes with an ExtendedEmitter for when a developer has made an emitter unavailable to you to extend / overwrite.

    It allows you to use the decorators and all the features of the typed emitter while not having full control of the origin emitter

    For example

    import { ExtendedEmitter } from '@jpbberry/typed-emitter'
    class MyOverrides extends ExtendedEmitter {
      @Event('message') // same concept as before!
      static onMessage (message: Message) { // make sure all of your methods are static, we aren't instantiating anything'Hello world!')
    // Now we just instantiate with the previous emitter
    const client = new Client() // this uses the default emitter
    MyOverrides.add(client) // this adds all of the events that were previously defined via the decorators

    Instiated ExtendedEmitter

    Especially useful when passing for example a manager to your event emitter, since you can't do this too well in static classes

    A real usecase:

    import { ExtendedEmitter } from '@jpbberry/typed-emitter'
    class MyOverrides extends ExtendedEmitter {
      // since it's instantiated you can pass whatever you want to the constructor and use it elsewhere
      constructor (private client: Client) {
      onMessage(msg: Message) { // make sure NOT to make this method static since you're instantiating
        if (msg.content === 'hello') {
          client.doSomething('hi!') // you'll have access to this client now
    const client = new Client()
    const overrides = new MyOverrides(client) // pass your options!
    overrides.add(client) // add the new overrides

    You can also use the applyToEmitter function if you want to use your own emitting options.


    npm i @jpbberry/typed-emitter

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