Scrolling up to the topmost in iOS's Safari causes problems with scrolling-up/down detection

I have the following Javascript code:

$(window).scroll(function() {
    if (window.innerWidth <= 768) {
        let scrollStatus = $(this).scrollTop();

        if (scrollStatus > lastScrollTop) {
            //do some stuffs

        else
            //do some other stuffs

        lastScrollTop = scrollStatus;
    }
});

So it worked well with non-mobile devices and Android devices. However, when I ran that on iOS's Safari and scroll to the topmost, it drags down the viewport by a little bit before bouncing up back when I release my finger hold. That bounce back up is detected by the above Javascript code as scrolling up and causes the trigger on the else section, which is undesirable. How do I fix this?

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