MikroEvent

Ultra-lightweight, Node.js-native way to handle events, both in-process (as EventEmitter events) or across systems via HTTP(S).

• Node.js native solution to work with event-driven architecture
• Easiest possible way to work with events in, or across, Node.js-based systems
• None of the learning curve and overhead of other eventing options
• Tiny (~1.2 KB gzipped)
• Zero dependencies
• High test coverage

Installation

npm install mikroevent -S

Usage

Quick Start

MikroEvent sends events to named targets using HTTP calls and/or internal, i.e. in-process events.

// ES5 format
const { MikroEvent } = require('mikroevent');
// ES6 format
import { MikroEvent } from 'mikroevent';

const mikroEvent = new MikroEvent();

mikroEvent.addTarget({
  name: 'internal',
  events: ['user.created']
});

const handler = () => { console.log('This runs in response to the user.created event') };

mikroEvent.on('user.created', handler);
//mikroEvent.once('user.created', handler); // Run event handler only once
//mikroEvent.off('user.created', handler);  // Remove event handler

await mikroEvent.emit('user.created', { id: '123', name: 'Test User' });

Check out the integration tests for a bigger, practical example of how MikroEvent works.

Updating a target

mikroEvent.updateTarget('system_a', { url: 'https://api.mydomain.com/userCreated', events: ['user.updated'] };

Add event to target

mikroEvent.addEventToTarget('system_a', ['user.updated', 'user.deleted']);

Removing a target

mikroEvent.removeTarget('system_a');

Receive events in the same system/process

Set up an event listener to react to events.

const handler = () => console.log('Run this when user.created is emitted');
mikroEvent.on('user.created', handler);

Receive events from other systems via HTTPS, transformed into an event

Handle an incoming event arriving over HTTP. Used for server integrations, when you want to manually handle the incoming event payload.

The processing will be async using process.nextTick() and running in a non-blocking fashion.

await mikroEvent.handleIncomingEvent({
  eventName: 'user.created',
  data: { id: '123', name: 'Test User' }
});

Receive events from other system via HTTPS

Create middleware for Express-style servers, i.e. using req and res objects. This is an approach that replaces using handleIncomingEvent() manually.

const middleware = mikroEvent.createMiddleware();
await middleware(req, res, next);

Configuration

You may also optionally instantiate MikroEvent with a custom error handling function.

const errorHandler = () => console.error('Run this on errors');
const mikroEvent = new MikroEvent({ errorHandler });

You can mute any non-critical message with the isSilent property set to false.

const mikroEvent = new MikroEvent({ isSilent: false });

License

MIT. See LICENSE file.