Angular Konami Service

konami.service.ts

import { isPlatformBrowser } from '@angular/common';
import {
  EventEmitter,
  inject,
  Injectable,
  Output,
  PLATFORM_ID,
} from '@angular/core';

@Injectable({ providedIn: 'root' })
export class KonamiService {
  #inputSequence: Array<string> = [];
  #konamiCode: Array<string> = [
    'ArrowUp',
    'ArrowUp',
    'ArrowDown',
    'ArrowDown',
    'ArrowLeft',
    'ArrowRight',
    'ArrowLeft',
    'ArrowRight',
    'b',
    'a',
  ];
  #platformId: {} = inject(PLATFORM_ID);
  #successful: boolean = false;

  get successful(): boolean {
    return this.#successful;
  }

  @Output() konamiCodeActivated = new EventEmitter<void>();

  constructor() {
    this.initialize();
  }

  initialize() {
    if (isPlatformBrowser(this.#platformId)) {
      this.#addWindowKeydownHandler();
    }
  }

  destroy() {
    this.#removeWindowKeydownHandler();
  }

  #addWindowKeydownHandler() {
    window.addEventListener(
      'keydown',
      this.#handleWindowKeydownEvent.bind(this)
    );
  }

  #removeWindowKeydownHandler() {
    window.removeEventListener(
      'keydown',
      this.#handleWindowKeydownEvent.bind(this)
    );
  }

  #handleWindowKeydownEvent(event: KeyboardEvent) {
    this.#inputSequence.push(event.key);

    if (this.#inputSequence.length > this.#konamiCode.length) {
      this.#inputSequence.shift();
    }

    if (this.#inputSequence.join(',') === this.#konamiCode.join(',')) {
      this.konamiCodeActivated.emit();
      this.#inputSequence = [];
      this.#successful = true;
    }
  }
}