Midder

My take on EventEmitter that works in both browser and Node, with some enhancements

Features

• Type-Safe: Full TypeScript support with strongly typed events
• Operation System: Transform, filter, and tap into events with simple API
• Universal: Works in both Node.js and browsers
• Targeted Emission: Emit to specific listeners
• Promise Support: Await on once(), because it's annoying to do otherwise
• AbortSignal: Cancel listeners with standard web APIs
• Wildcard Events: Listen to all events with *

Installation

npm install midder

Building

npm run build

Test

npm run test

Example

npm run example

Quick Start

import { EventEmitter } from 'midder';

// Define your event types
interface MyEvents {
  userLogin: { userId: string; timestamp: number };
  dataUpdate: { id: string; value: any };
}

const emitter = new EventEmitter<MyEvents>();

// Add listeners
const listenerId = emitter.on('userLogin', (data) => {
  console.log(`User ${data.userId} logged in at ${data.timestamp}`);
});

// Emit events
emitter.emit('userLogin', {
  userId: 'user123',
  timestamp: Date.now()
});

Operation System

Transform and process events with powerful operation:

emitter.operation('userLogin')
  .transform((data) => ({ ...data, processed: true }))
  .filter((data) => {
    console.log(data.processed);  // Type safe transformation
    return data.userId.length > 0;
  })
  .tap((data) => console.log('Processing:', data.userId))
  .log('User login processed');

ID or reference based controls

const emitter = new EventEmitter<EventMap>();
const id = emitter.on('data', (data) => {
    // ...
});

const callback = (data) => JSON.stringify(data);
emitter.on('data', callback);

// Targeted emissions based on ID (because why not)
emitter.emitToListener('data', { hello: 'world!' }, id);

// Both supported
emitter.off('data', id);
emitter.off('data', callback);

Promise-based once()

// Wait for next event
const userData = await emitter.once('userLogin');

// With timeout
const userData = await emitter.once('userLogin', { timeout: 5000 });

// With AbortSignal
const controller = new AbortController();
const userData = await emitter.once('userLogin', { signal: controller.signal });

API Reference

EventEmitter Methods

• on(event, listener, signal?) - Add event listener
• off(event, idOrHandler) - Remove event listener
• once(event, options?) - Promise-based single-use listener
• emit(event, data) - Emit event to all listeners
• emitToListener(event, data, listenerId) - Emit to specific listener
• operation(event) - Get operation builder for event
• listenerCount(event) - Get number of listeners
• removeAllListeners(event?) - Remove all listeners
• eventNames() - Get list of events with listeners

Operation Methods

• transform(handler) - Transform event data
• filter(predicate) - Filter events conditionally
• tap(handler) - Execute side effects
• debounce(delayMs) - Add debounce to events
• throttle(delayMs) - Add throttle to events
• log(message?) - Log events to console

License

MIT © [kjkwan1]