@carry0987/event-emitter NPM

EventEmitter-JS

EventEmitter is a TypeScript library that provides a simple yet powerful event-handling mechanism. It allows you to define and manage events in your application, supporting standard event operations such as on, off, emit, once, and more.

Features

Lightweight and easy to use
Type-safe event handling
Support for one-time event listeners with once
Flexible event management
Support for both synchronous and asynchronous event listeners

Installation

To install the EventEmitter library, use the following command:

npm i @carry0987/event-emitter -D

Usage

Importing the Library

First, import the EventEmitter class into your TypeScript file:

import { EventEmitter } from '@carry0987/event-emitter';

Defining Event Types

Define your event types for type safety. For example:

interface MyEvents {
    greet: [string];
    farewell: [string];
}

Creating an EventEmitter Instance

Create an instance of EventEmitter with your event types:

const emitter = new EventEmitter<MyEvents>();

Adding Event Listeners

Use the on method to add event listeners:

emitter.on('greet', (message) => {
    console.log(message);
});

Emitting Events

Emit events using the emit method:

emitter.emit('greet', 'Hello, world!');

Removing Event Listeners

Remove event listeners with the off method:

const greetListener = (message: string) => {
    console.log(message);
};

emitter.on('greet', greetListener);
emitter.off('greet', greetListener);

One-time Event Listeners

Use the once method to add a listener that will be called only once:

emitter.once('farewell', (message) => {
    console.log(message);
});

emitter.emit('farewell', 'Goodbye, world!'); // Listener will be called
emitter.emit('farewell', 'Goodbye again!');  // Listener will not be called

Using Asynchronous Event Listeners

Add asynchronous event listeners using the on or once method:

emitter.on('greet', async (message) => {
    await new Promise(resolve => setTimeout(resolve, 1000));
    console.log(`Async Listener: ${message}`);
});

emitter.emit('greet', 'Hello, async world!').then(() => {
    console.log('All async listeners have been called.');
});

API

`on(event: EventName, listener: (...args: any[]) => void | Promise<void>): EventEmitter`

Registers an event listener for the specified event.

`off(event: EventName, listener: (...args: any[]) => void | Promise<void>): EventEmitter`

Removes the specified event listener.

`emit(event: EventName, ...args: any[]): Promise<boolean>`

Emits the specified event, calling all registered listeners with the provided arguments. Returns a promise that resolves to true if there were listeners, and false otherwise.