simple event emitter

eventemitter.ts

/**
 * Declare Simple EventEmitter
 * No Limitation, No expandable. 
 * If you need to implement more or genric, please contact hunje
 */

type EventHandlerMap = {
  [key:string]:Function[];
}

class EventEmitter {
  private eventHandlers:EventHandlerMap = {};
  private eventOnceHanders:EventHandlerMap = {};

  public addListener(type:string, handler:Function) {
    const handlers = this.eventHandlers[type];
    if (!handlers) {
      this.eventHandlers[type] = [handler];
    } else {
      this.eventHandlers[type].push(handler);
    }
  }

  public runOnce(type:string, handler:Function) {
    const handlers = this.eventOnceHanders[type];
    if (!handlers) {
      this.eventOnceHanders[type] = [handler];
    } else {
      this.eventOnceHanders[type].push(handler);
    }
  }

  public removeListener(type:string, handler:Function) {
    if (type in this.eventHandlers) {
      const index = this.eventHandlers[type].indexOf(handler);
      if (index >= 0) {
        this.eventHandlers[type].splice(index, 1);
      }
    }

    if (type in this.eventOnceHanders) {
      const index = this.eventOnceHanders[type].indexOf(handler);
      if (index >= 0) {
        this.eventOnceHanders[type].splice(index, 1);
      }
    }
  }

  public removeListeners(type:string) {
    if (type in this.eventHandlers) {
      this.eventHandlers[type] = [];
      this.eventOnceHanders[type] = [];
    }
  }

  public emit(type:string) {
    if (this.eventHandlers[type]) {
      for (const handler of this.eventHandlers[type]) {
        handler();
      }
    }
    this.once(type);
  }

  private once(type:string) {
    const handlers = this.eventOnceHanders[type];
    this.eventOnceHanders[type] = [];
    if (handlers) {
      for (const handler of handlers) {
        handler();
      }
    }
  }
}

export {
  EventEmitter
}