pubsub.ts

interface IPubSub<T> {
  publish(value: T): void;

  subscribe(subscriber: Subscriber<T>): Disposer;
}

type Subscriber<T> = (value: T): void;

type Disposer = () => void;

class PubSub<T> implements IPubSub<T> {
  private subscribers: ISubscriber<T>[] = [];

  publish(value: T): void {
    this.subscribers.forEach((subscriber) => {
      subscriber(value);
    });
  }

  subscribe(subscriber: Subscriber<T>): Disposer {
    this.subscribers.push(subscriber);

    return () => {
      const idx = this.subscribers.findIndex((s) => s === subscriber);
      this.subscribers.splice(idx, 1);
    };
  }
}

// Example

const pubsub = new PubSub<string>();

pubsub.publish("greeting");

const dispose = pubsub.subscribe((value: string) => {
  console.info(value)
});

dispose();