const appScroll = () => {
    let latestKnownScrollY = 0,
        ticking = false;

    const _onScroll = () => {
        latestKnownScrollY = window.pageYOffset;
        _requestTick();
    };

    const _requestTick = () => {
        if (!ticking) {
            window.requestAnimationFrame(_update);
        }
        ticking = true;
    };

    const _update = () => {
        ticking = false;
        const currentScrollY = latestKnownScrollY;

        // Update functions here. Pass on currentScrollY as positionVariable
    };

    // scroll mousewheel wheel
    window.onscroll = (e) => {
        _onScroll();
    };
};