tiny-typed-emitter

Fully type-checked EventEmitter

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tiny-typed-emitter
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Readme

tiny-typed-emitter

Have your events and their listeners type-checked with no overhead.

npm version

Install

Simply add the dependency using npm:

$ npm i tiny-typed-emitter

or using yarn:

$ yarn add tiny-typed-emitter

Usage

  1. import tiny-typed-emitter library:
import { TypedEmitter } from 'tiny-typed-emitter';
  1. define events and their listener signatures (note: quotes around event names are not mandatory):

    interface MyClassEvents {
     'added': (el: string, wasNew: boolean) => void;
     'deleted': (deletedCount: number) => void;
    }
    
  2. on this step depending on your use case, you can:

  • define your custom class extending EventEmitter:
    class MyClass extends TypedEmitter<MyClassEvents> {
      constructor() {
        super();
      }
    }
    
  • create new event emitter instance:
    const emitter = new TypedEmitter<MyClassEvent>();
    

Generic events interface

To use with generic events interface:

interface MyClassEvents<T> {
  'added': (el: T, wasNew: boolean) => void;
}

class MyClass<T> extends TypedEmitter<MyClassEvents<T>> {

}

Compatible subclasses with different events

The type of eventNames() is a superset of the actual event names to make subclasses of a TypedEmitter that introduce different events type compatible. For example the following is possible:

class Animal<E extends ListenerSignature<E>=ListenerSignature<unknown>> extends TypedEmitter<{spawn: () => void} & E> {
  constructor() {
    super();
  }
}

class Frog<E extends ListenerSignature<E>> extends Animal<{jump: () => void} & E> {
}

class Bird<E extends ListenerSignature<E>> extends Animal<{fly: () => void} & E> {
}

const animals: Animal[] = [new Frog(), new Bird()];

No Overhead

Library adds no overhead. All it does is it simply reexports renamed EventEmitter with customized typings. You can check lib/index.js to see the exported code.

If you find any bugs or have a feature request, please open an issue on github!

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