जेनेरिक इवेंट एमिटर क्लास

interface Events { login: { userId: string }; logout: void }
// class TypedEmitter<Events> will manage handlers safely.
console.log("building a typed emitter");

type Handler<E, K extends keyof E> = (payload: E[K]) => void;
// E[K] is the payload type for event K in map E.
console.log("handler typed by E[K]");

class TypedEmitter<E> {
  private listeners: { [K in keyof E]?: Array<(p: E[K]) => void> } = {};
}
console.log("listeners map ready");

class TypedEmitter<E> {
  private listeners: { [K in keyof E]?: Array<(p: E[K]) => void> } = {};
  on<K extends keyof E>(event: K, handler: (p: E[K]) => void): void {
    (this.listeners[event] ||= []).push(handler);
  }
}
console.log("on implemented");

class TypedEmitter<E> {
  private listeners: { [K in keyof E]?: Array<(p: E[K]) => void> } = {};
  on<K extends keyof E>(e: K, h: (p: E[K]) => void) { (this.listeners[e] ||= []).push(h); }
  emit<K extends keyof E>(e: K, payload: E[K]): void {
    (this.listeners[e] || []).forEach(h => h(payload));
  }
}
console.log("emit implemented");

class TypedEmitter<E> {
  private listeners: { [K in keyof E]?: Array<(p: E[K]) => void> } = {};
  on<K extends keyof E>(e: K, h: (p: E[K]) => void) { (this.listeners[e] ||= []).push(h); }
  off<K extends keyof E>(e: K, h: (p: E[K]) => void) {
    this.listeners[e] = (this.listeners[e] || []).filter(x => x !== h);
  }
}
console.log("off implemented");

class TypedEmitter<E> {
  private listeners: { [K in keyof E]?: Array<(p: E[K]) => void> } = {};
  on<K extends keyof E>(e: K, h: (p: E[K]) => void) { (this.listeners[e] ||= []).push(h); }
  off<K extends keyof E>(e: K, h: (p: E[K]) => void) { this.listeners[e] = (this.listeners[e] || []).filter(x => x !== h); }
  emit<K extends keyof E>(e: K, p: E[K]) { (this.listeners[e] || []).forEach(h => h(p)); }
}
console.log("TypedEmitter complete");

class TypedEmitter<E> {
  private listeners: { [K in keyof E]?: Array<(p: E[K]) => void> } = {};
  on<K extends keyof E>(e: K, h: (p: E[K]) => void) { (this.listeners[e] ||= []).push(h); }
  emit<K extends keyof E>(e: K, p: E[K]) { (this.listeners[e] || []).forEach(h => h(p)); }
}
interface Events { login: { userId: string } }
const bus = new TypedEmitter<Events>();
bus.on("login", p => console.log("hi", p.userId));
bus.emit("login", { userId: "u1" });

class TypedEmitter<E> {
  private listeners: { [K in keyof E]?: Array<(p: E[K]) => void> } = {};
  on<K extends keyof E>(e: K, h: (p: E[K]) => void) { (this.listeners[e] ||= []).push(h); }
  emit<K extends keyof E>(e: K, p: E[K]) { (this.listeners[e] || []).forEach(h => h(p)); }
}
interface Events { ping: { at: number } }
const bus = new TypedEmitter<Events>();
// bus.emit("pong", { at: 1 }); // Error
bus.emit("ping", { at: 1 });
console.log("typed bus");

class TypedEmitter<E> {
  private listeners: { [K in keyof E]?: Array<(p: E[K]) => void> } = {};
  on<K extends keyof E>(e: K, h: (p: E[K]) => void) { (this.listeners[e] ||= []).push(h); }
  emit<K extends keyof E>(e: K, p: E[K]) { (this.listeners[e] || []).forEach(h => h(p)); }
}
interface Events { tick: { n: number } }
const bus = new TypedEmitter<Events>();
bus.on("tick", p => console.log("a", p.n));
bus.on("tick", p => console.log("b", p.n));
bus.emit("tick", { n: 7 });

class TypedEmitter<E> {
  private listeners: { [K in keyof E]?: Array<(p: E[K]) => void> } = {};
  on<K extends keyof E>(e: K, h: (p: E[K]) => void) { (this.listeners[e] ||= []).push(h); }
  emit<K extends keyof E>(e: K, p: E[K]) { (this.listeners[e] || []).forEach(h => h(p)); }
}
const bus = new TypedEmitter<{ go: void }>();
bus.on("go", () => console.log("go!"));
bus.emit("go", undefined as void);

class TypedEmitter<E> {
  private listeners: { [K in keyof E]?: Array<(p: E[K]) => void> } = {};
  on<K extends keyof E>(e: K, h: (p: E[K]) => void) { (this.listeners[e] ||= []).push(h); }
  emit<K extends keyof E>(e: K, p: E[K]) { (this.listeners[e] || []).forEach(h => h(p)); }
}
const bus = new TypedEmitter<{ hi: { name: string } }>();
bus.on("hi", p => console.log(p.name));
bus.emit("hi", { name: "Ada" });