Eventail

An event emitter abstract class with priority support

What it does

• 🎯 Priority-based event handling
• ⚡ Single and one-time event listeners
• 🔄 Context binding support
• 📦 TypeScript support
• 🧪 No external dependencies

This is an abstract class, so you need to extend it to use it. The emit method is protected, meaning only your class can trigger events internally.

Installation

npm install eventail

Usage

Basic Example

import { Eventail } from 'eventail';

class Player extends Eventail {
  private level = 1;
  private experience = 0;

  public gainExperience(amount: number) {
    this.experience += amount;
    this.emit('experienceGained', amount, this.experience);

    if (this.experience >= this.level * 100) {
      this.level++;
      this.experience = 0;
      this.emit('leveledUp', this.level);
    }
  }
}

const player = new Player();

player.on('experienceGained', (amount, total) => {
  console.log(`Gained ${amount} XP (Total: ${total})`);
});

player.on('leveledUp', (level) => {
  console.log(`Level up! Now level ${level}`);
});

player.gainExperience(150);

With Context and Priority

const ui = {
  showMessage(text: string) {
    console.log(`[UI] ${text}`);
  }
};

// Lower numbers = higher priority
player.on('leveledUp', function(level) {
  this.showMessage(`Reached level ${level}`);
}, ui, -10);

One-Time Listeners

// Runs only once
player.once('firstDeath', () => {
  console.log('This only happens once');
});

Removing Listeners

const handler = (data) => console.log(data);
player.on('event', handler);
player.off('event', handler); // Remove specific listener
player.off('event'); // Remove all listeners for this event

API

on(type: string | number, callback: Function, context?: object, priority?: number)

Adds an event listener. Lower priority numbers execute first.

once(type: string | number, callback: Function, context?: object, priority?: number)

Adds a listener that removes itself after first execution.

off(type: string | number, callback?: Function, context?: object)

Removes listener(s). Without callback, removes all listeners for the event.

protected emit(type: string | number, ...args: any[])

Emits an event. Only available inside your class that extends Eventail.

Notes

• Listeners with the same priority may execute in any order
• The class uses WeakMap internally, so context objects can be garbage collected normally
• Event types can be strings or numbers
• This is just one way to handle events - there are probably better solutions for your specific use case

License

MIT © jango