@vegajs/event-bus
v1.0.0-beta.31
Published
A flexible and typed Event Bus implementation for TypeScript and JavaScript projects. It facilitates communication between components and modules without tight coupling.
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@vegajs/event-bus
A flexible and typed Event Bus implementation for TypeScript projects. This library provides a simple interface to manage events and listeners, allowing communication between different parts of your application without tight coupling.
Installation
Install the package via npm:
npm install @vegajs/event-bus
Usage
Basic Setup
You can define your own event types and data structure, and use the EventBus
to emit and listen to events. Here's an example:
import { EventBus } from 'your-event-bus-package';
// Define the events for your application
type MyAppEvents = {
'app:start': void;
'user:login': { username: string };
'data:update': { newData: any };
};
// Create an instance of EventBus
const eventBus = new EventBus<MyAppEvents>();
// Subscribing to an event
eventBus.on('user:login', (event) => {
console.log(`User logged in: ${event.username}`);
});
// Emitting an event
eventBus.emit('user:login', { username: 'john_doe' });
// Unsubscribing from an event
const handler = (event: { username: string }) => console.log(`User logged in: ${event.username}`);
eventBus.on('user:login', handler);
eventBus.off('user:login', handler);
Example of Multiple Event Types
You can also work with multiple types of events in a type-safe way.
// Define a new set of events
type OtherEvents = {
'error': { message: string };
'notification': { text: string };
};
const anotherBus = new EventBus<OtherEvents>();
// Subscribing to different events
anotherBus.on('error', (event) => {
console.error(`Error occurred: ${event.message}`);
});
anotherBus.on('notification', (event) => {
console.log(`Notification: ${event.text}`);
});
// Emitting events
anotherBus.emit('error', { message: 'Something went wrong!' });
anotherBus.emit('notification', { text: 'New message received' });
Asynchronous Events
The EventBus
also supports asynchronous event handlers if necessary:
const asyncBus = new EventBus<MyAppEvents>();
asyncBus.on('app:start', async () => {
await new Promise(resolve => setTimeout(resolve, 1000));
console.log('App started after 1 second');
});
asyncBus.emit('app:start', undefined);
Handling Events with void
Type
If you have events that do not carry any data (i.e., void
events), you can emit them without providing an argument:
type VoidEvents = {
'app:stop': void;
};
const voidBus = new EventBus<VoidEvents>();
voidBus.on('app:stop', () => {
console.log('App stopped');
});
voidBus.emit('app:stop', undefined);
API
on
on<K extends keyof EventMap>(eventName: K, handler: (event: EventMap[K]) => void): void;
- eventName: The name of the event to listen for.
- handler: The function to execute when the event is emitted.
off
off<K extends keyof EventMap>(eventName: K, handler: (event: EventMap[K]) => void): void;
- eventName: The name of the event to stop listening for.
- handler: The function to remove from the listener list.
emit
emit<K extends keyof EventMap>(eventName: K, event: EventMap[K]): void;
- eventName: The name of the event to emit.
- event: The data to pass to the listeners of the event.