@known-as-bmf/hookable/src/event-emitter.ts.ignore

Function hooking utility.

type Action<Args extends readonly any[]> = (...args: Args) => void;

interface EventTypes {
  [name: string]: readonly any[];
}

interface EventCache {
  [name: string]: Set<Action<any[]>>;
}

export class EventEmitter<T extends EventTypes> {
  private _cache: EventCache = {};

  public emit<E extends keyof T>(name: E, args: T[E]): void {
    if (!this._cache[name as string]) {
      return;
    }

    this._cache[name as string].forEach((callback) => {
      callback(...args);
    });
  }

  public on<E extends keyof T>(name: E, callback: Action<T[E]>): void {
    if (!this._cache[name as string]) {
      this._cache[name as string] = new Set<Action<any[]>>();
    }
    this._cache[name as string].add(callback);
  }

  public off<E extends keyof T>(name: E, callback: Action<T[E]>): void {
    if (!this._cache[name as string]) {
      return;
    }
    this._cache[name as string].add(callback);
  }
}

const t = new EventEmitter<{ test: [someValue: string] }>();

t.emit('test', ['a']);

const handler = (): void => {};
t.on('test', handler);
t.off('test', handler);