TypedEmitter

TypedEmitter is the base class that gives every other class in three-start its event API. ThreeContext, ContextModule, and Object3DBehaviour all extend it.

What it does

• Wraps an eventemitter3 instance internally — the proven small/fast emitter, ~1KB minified.
• Lazy initialization — the inner emitter is only allocated on the first on / once. Classes that extend TypedEmitter but never have a subscriber pay only one reference slot per instance.
• Type-safe events via the <T extends EventMap> generic. Keys become valid event arguments, tuple values type the listener payload.
• Encapsulation by design — on / off / once are public so anyone can subscribe; emit is protected so only the owning class fires its own events. No external code can fake an event.

type HealthEvents = {
  damaged: [amount: number, source: string];
  died: [];
};

class Health extends Object3DBehaviour<HealthEvents> {
  hp = 100;
  hit(damage: number, by: string) {
    this.hp -= damage;
    this.emit("damaged", damage, by);     // ✅ inside the class
    if (this.hp <= 0) this.emit("died");  // ✅
  }
}

const health = getComponent(player, Health)!;
health.on("damaged", (amount, by) => console.log(`-${amount} from ${by}`));
health.emit("damaged", 10, "x");          // ❌ compile error: emit is protected

The default for T is {} — a class without an explicit event map can't legitimately call on / emit (compile error from keyof {} = never). This is the type-level opt-in pattern.

Methods