@mdingena/tiny-typed-emitter

tiny-typed-emitter

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

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;
}

1. 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.