evb

A minimal, dependency-free JavaScript event bus for decoupled communication between modules.

Check the Atuin Demo to see experience it in action (is under the hood).

Overview

evb (Event Bus) provides a simple publish/subscribe mechanism for JavaScript applications. It is designed to be lightweight and easy to integrate, making it suitable for small projects, prototypes, or educational purposes. The API is intentionally minimal, focusing on core event bus functionality without extra features or complexity.

I had a handful of little browser-oriented apps which needed an event bus. It didn't really justify a 3rd party feature-rich lib, so I threw together the minimum necessary (as a 1st party lib). It does include basic state management and Redux-style util methods, but these haven't really been tried in the wild.

Features

• Publish/subscribe pattern for decoupled communication
• No external dependencies
• Works in both browser and Node.js environments
• Simple, readable codebase

Installation

You can install evb locally (for development or as a dependency):

npm install ../evb

Or, if published to npm:

npm install evb

Usage

import { on, off, emit } from 'evb';

// Subscribe to an event
on('my-event', (data) => {
  console.log('Received:', data);
});

// Emit an event
emit('my-event', { foo: 'bar' });

// Unsubscribe
off('my-event', handler);

API

• on(eventName, handler): Register a handler for an event.
• off(eventName, handler): Remove a handler for an event.
• emit(eventName, data): Emit an event with optional data.

Limitations

• No wildcard or namespaced events.
• No event replay or history.
• No built-in error handling for handlers.
• Not intended for large-scale or production-critical systems.

Project Structure

evb/
├── src/
│   ├── event-bus.js
│   ├── event-constants.js
│   ├── state-utils.js
│   ├── store.js
│   └── index.js
├── test/
│   └── unit/
├── README.md
├── package.json
└── ...

Testing

Unit tests are provided using Vitest. To run the tests:

npm test

Coverage

Test coverage reports are generated using Vitest's built-in coverage tool. To generate a coverage report (including lcov and HTML formats):

npm run coverage

The HTML report can be viewed by opening coverage/index.html in your browser. The lcov report is available at coverage/lcov.info for integration with services like Coveralls.

License

Code : MIT License. Docs : public domain, attribution appreciated.

© 2025 Danny Ayers (@danja), Anthropic Claude, GitHub Copilot and Canine Claudio. A hyperdata.it thing.