Typed events in typescript

events.ts

type EventMap = {
  loadMore: { lastMessage: sting };
};

class TypedEventTarget<T extends Record<string, any>> {
  private listeners: Partial<{ [K in keyof T]: ((event: T[K]) => void)[] }> = {};

  addEventListener<K extends keyof T>(type: K, listener: (event: T[K]) => void) {
    if (!this.listeners[type]) {
      this.listeners[type] = [];
    }
    this.listeners[type]!.push(listener);
  }

  removeEventListener<K extends keyof T>(type: K, listener: (event: T[K]) => void) {
    if (!this.listeners[type]) return;
    this.listeners[type] = this.listeners[type]!.filter((l) => l !== listener);
  }

  dispatchEvent<K extends keyof T>(type: K, event: T[K]) {
    if (!this.listeners[type]) return;
    this.listeners[type]!.forEach((listener) => listener(event));
  }
}

export const chatEvents = new TypedEventTarget<EventMap>();

chatEvents.dispatchEvent("loadMore", { lastMessage: "somemessageid" });