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

Simply add the dependency using npm:

$ npm i tiny-typed-emitter

or using yarn:

$ yarn add tiny-typed-emitter

1. import tiny-typed-emitter library:

import { TypedEmitter } from 'tiny-typed-emitter';

2. 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; }

3. 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>();

To use with generic events interface:

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

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()];

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.