Konami code for typescript

konami.ts

export const Konami = (() => {
    // up, up, down, down, left, right, left, right, b, a, enter
    const SEQUENCE: Array<number> = [
        38,
        38,
        40,
        40,
        37,
        39,
        37,
        39,
        66,
        65,
        13,
    ];

    let head: number = 0;
    let isActive: boolean = false;

    let callback: Function | undefined;

    const start = (cb: Function): void => {
        if (isActive) {
            return;
        }

        window.addEventListener("keydown", onKeyDown);

        callback = cb;
        isActive = true;
    };

    const stop = (): void => {
        if (!isActive) {
            return;
        }

        isActive = false;

        window.removeEventListener("keydown", onKeyDown);
    };

    const onKeyDown = (event: any) => {
        if (event.keyCode === SEQUENCE[head]) {
            head++;

            if (head === SEQUENCE.length) {
                if (callback instanceof Function) {
                    callback();
                }
                head = 0;
            }
        } else {
            head = 0;
        }
    };

    return {
        start,
        stop,
    };
})();


// how to call it in the application

export const App = () => {

    const [konamiActive, setKonamiActive] = useState(false);

    useEffect(() => {
        console.log(konamiActive)

        Konami.start(() => { 
            setKonamiActive((currValue) => !currValue);
        });

    },[konamiActive])

    
    return (
        <>
            // make <KonamiBackground/> as one component for screen show of konamicode
            {konamiActive && <KonamiBackground/>} 
        </>
    );
}