weakeventemitter/index.d.ts

WeakEventEmitter focuses on using weak references and keeping performance while maintaining a Node.js AND browser compatible interface.

type EventNames<T extends string | symbol | { [K in string | symbol]: any[] }> = T extends string | symbol ? T : keyof T;
type EventArgs<T extends string | symbol | { [K in string | symbol]: any[] }, K extends EventNames<T>> = T extends string | symbol ? any[] : K extends keyof T ? T[K] : never;

/**
 * Minimal `WeakEventEmitter` interface that is molded against the Node.js
 * `WeakEventEmitter` interface.
 */
declare class WeakEventEmitter<EventTypes extends string | symbol | { [K in keyof EventTypes]: any[] } = string | symbol> {
  static prefixed: string | boolean;

  /**
   * Return an array listing the events for which the emitter has registered
   * listeners.
   */
  eventNames(): Array<EventNames<EventTypes>>;

  /**
   * Return the listeners registered for a given event.
   */
  listeners<T extends EventNames<EventTypes>>(event: T): Array<WeakEventEmitter.ListenerFn<EventArgs<EventTypes, T>>>;

  /**
   * Return the number of listeners listening to a given event.
   */
  listenerCount(event: EventNames<EventTypes>): number;

  /**
   * Calls each of the listeners registered for a given event.
   */
  emit<T extends EventNames<EventTypes>>(event: T, ...args: EventArgs<EventTypes, T>): boolean;

  /**
   * Add a listener for a given event.
   */
  on<T extends EventNames<EventTypes>>(event: T, fn: WeakEventEmitter.ListenerFn<EventArgs<EventTypes, T>>, context?: any): this;
  addListener<T extends EventNames<EventTypes>>(event: T, fn: WeakEventEmitter.ListenerFn<EventArgs<EventTypes, T>>, context?: any): this;

  /**
   * Add a one-time listener for a given event.
   */
  once<T extends EventNames<EventTypes>>(event: T, fn: WeakEventEmitter.ListenerFn<EventArgs<EventTypes, T>>, context?: any): this;

  /**
   * Remove the listeners of a given event.
   */
  removeListener<T extends EventNames<EventTypes>>(event: T, fn?: WeakEventEmitter.ListenerFn<EventArgs<EventTypes, T>>, context?: any, once?: boolean): this;
  off<T extends EventNames<EventTypes>>(event: T, fn?: WeakEventEmitter.ListenerFn<EventArgs<EventTypes, T>>, context?: any, once?: boolean): this;

  /**
   * Remove all listeners, or those of the specified event.
   */
  removeAllListeners(event?: EventNames<EventTypes>): this;
}

declare namespace WeakEventEmitter {
  export interface ListenerFn<Args extends any[] = any[]> {
    (...args: Args): void;
  }

  export interface WeakEventEmitterStatic {
    new<EventTypes extends string | symbol | { [K in keyof EventTypes]: any[] } = string | symbol>(): WeakEventEmitter<EventTypes>;
  }

  export const WeakEventEmitter: WeakEventEmitterStatic;
}

export = WeakEventEmitter;