minimal-typed-event-emitter

A minimalistic package that allows you to define typed event names and callbacks on EventEmitter.

Documentation of original EventEmitter is preserved.
Listener parameter names are supported.
All member methods of EventEmitter are supported.

(You can use any parameter name you wish)

Usage

Installation

npm install minimal-typed-event-emitter --save-dev
# or:
yarn add minimal-typed-event-emitter --dev

When you want an EventEmitter instance:

import { TypedEventEmitter } from "minimal-typed-event-emitter";

type Events = {
  "event-with-no-parameters": [];
  "event-with-one-parameter": [param1: string]; // You can use any parameter name you wish
  "event-with-two-parameters-one-optional": [param1: number, param2?: { inner: string }];
};

const eventEmitter = new TypedEventEmitter<Events>();
// Also works: const eventEmitter = new EventEmitter() as TypedEventEmitter<Events>;

eventEmitter.on("event-with-no-parameters", () => {});
eventEmitter.on("event-with-one-parameter", (a) => {});
eventEmitter.on("event-with-two-parameters-one-optional", (a, b) => {});

eventEmitter.emit("event-with-two-parameters-one-optional", 1);
eventEmitter.emit("event-with-two-parameters-one-optional", 1, 2); // Error: Argument of type 'number' is not assignable to parameter of type '{ inner: string; }'.ts(2345)

When you want to extend EventEmitter:

import { TypedEventEmitter } from "minimal-typed-event-emitter";

type Events = {
  "event-with-no-parameters": [];
  "event-with-one-parameter": [param1: string]; // You can use any parameter name you wish
  "event-with-two-parameters-one-optional": [param1: number, param2?: { inner: string }];
};

class MyEventEmitter extends TypedEventEmitter<Events> {
  // ...
}

const myEventEmitter = new MyEventEmitter();

myEventEmitter.on("event-with-no-parameters", () => {});
myEventEmitter.on("event-with-one-parameter", (a) => {});
myEventEmitter.on("event-with-two-parameters-one-optional", (a, b) => {});

myEventEmitter.emit("event-with-two-parameters-one-optional", 1);
myEventEmitter.emit("event-with-two-parameters-one-optional", 1, 2); // Error: Argument of type 'number' is not assignable to parameter of type '{ inner: string; }'.ts(2345)