An initial implementation of keyboard state for my ECSY game.

ecsy-keyboard-system.ts

class KeyState {
  isPressed: boolean;
  timeSinceChanged: number;

  constructor(isPressed) {
    this.isPressed = isPressed;
    this.timeSinceChanged = 0;
  }
}

type KeyboardComponentProps = {
  keys: Map<number, KeyState>;
};

class KeyboardComponent extends Component<KeyboardComponentProps> {
  static schema = {
    keys: { type: Types.Ref, default: new Map() },
  };

  setKey = (keyCode: number, isPressed: boolean) => {
    let key: KeyState;

    if (this.keys.has(keyCode)) {
      key = this.keys.get(keyCode);

      const hasStateChanged = key.isPressed != isPressed;
      if (hasStateChanged) key.timeSinceChanged = 0;

      key.isPressed = isPressed;
    } else {
      key = new KeyState(isPressed);
    }

    console.log(key);
    this.keys.set(keyCode, key);
  };

  getKey = (keyCode) => {
    this.keys.get(keyCode);
  };

  setKeyFromEvent = (event: KeyboardEvent) => {
    const { keyCode, type } = event;

    const isPressed = type === "keydown";
    this.setKey(keyCode, isPressed);
  };

  keys: Map<number, KeyState>;
}

class KeyboardSystem extends System {
  static queries = {
    keyboard: {
      components: [KeyboardComponent],
      listen: {
        added: true,
        removed: true,
      },
    },
  };

  execute(delta): void {
    const { added, removed, results } = this.queries.keyboard;

    added.forEach((entity) => {
      const keyboard = entity.getComponent<KeyboardComponent>(KeyboardComponent);
      window.addEventListener("keydown", keyboard.setKeyFromEvent);
      window.addEventListener("keyup", keyboard.setKeyFromEvent);
    });

    removed.forEach((entity) => {
      const keyboard = entity.getComponent<KeyboardComponent>(KeyboardComponent);
      window.removeEventListener("keydown", keyboard.setKeyFromEvent);
      window.removeEventListener("keyup", keyboard.setKeyFromEvent);
    });

    results.forEach((entity) => {
      const keyboard = entity.getComponent<KeyboardComponent>(KeyboardComponent);
      keyboard.keys.forEach((key) => {
        key.timeSinceChanged += delta;
      });
    });
  }
}