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barfi/typed-eventemitter-subclass.md

Last active July 26, 2023 17:12
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Revisions

  1. barfi revised this gist Jul 26, 2023. 1 changed file with 9 additions and 3 deletions.
    12 changes: 9 additions & 3 deletions typed-eventemitter-subclass.md
    View file
    Original file line number Diff line number Diff line change
    @@ -4,7 +4,7 @@
    type CustomEmitterEvents = {
    eventA: (payload: number) => void
    eventB: (payload: string) => void
    eventC: (arg: boolean, msg: string) => boolean
    eventC: (arg: boolean, msg: string) => void
    }

    // Interface of your sublcass, matches the EventEmitter method signatures
    @@ -26,7 +26,13 @@ interface CustomEmitter {

    class SuperEmitter extends EventEmitter implements CustomEmitter {

    // your stuff...
    // Override parent class on method
    override on<T extends keyof CustomEmitterEvents>(event: T, listener: CustomEmitterEvents[T]): this {
    super.on(event, listener)
    return this
    }

    // other stuff...

    }

    @@ -39,7 +45,7 @@ emitter.on('eventA', (payload: number) => {
    })

    emitter.on('eventC', (arg: boolean, msg: string) => {
    // your stuff...
    // your stuff...
    })

    ```
  2. barfi created this gist Jul 26, 2023.
    47 changes: 47 additions & 0 deletions typed-eventemitter-subclass.md
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,47 @@
    ```ts
    // Map all your event names with their handlers

    type CustomEmitterEvents = {
    eventA: (payload: number) => void
    eventB: (payload: string) => void
    eventC: (arg: boolean, msg: string) => boolean
    }

    // Interface of your sublcass, matches the EventEmitter method signatures

    interface CustomEmitter {

    // Matches EventEmitter.on
    on<T extends keyof CustomEmitterEvents>(event: T, listener: CustomEmitterEvents[T]): this

    // Matches EventEmitter.off
    off<T extends keyof CustomEmitterEvents>(event: T, listener: CustomEmitterEvents[T]): this

    // Matches EventEmitter.emit
    emit<T extends keyof CustomEmitterEvents>(event: T, ...args: Parameter<CustomEmitterEvents[T]>: boolean

    }

    // Define your subclass

    class SuperEmitter extends EventEmitter implements CustomEmitter {

    // your stuff...

    }

    // You can use it like below

    const emitter = new SuperEmitter()

    emitter.on('eventA', (payload: number) => {
    // your stuff...
    })

    emitter.on('eventC', (arg: boolean, msg: string) => {
    // your stuff...
    })

    ```
    THX to [BRIAN MANCINI](https://www.derpturkey.com/typescript-and-node-js-eventemitter/) for his idea.