jquery判断鼠标滚动方向

$(document).ready(function() {
    var lastScrollTop = 0;

    $(window).scroll(function() {
        var st = $(this).scrollTop();

        if (st > lastScrollTop) {
            // 向下滚动
            console.log("向下滚动");
        } else {
            // 向上滚动
            console.log("向上滚动");
        }

        lastScrollTop = st;
    });
});

function throttle(func, wait) {
    var timeout = null;
    return function() {
        if (!timeout) {
            timeout = setTimeout(function() {
                func.apply(this, arguments);
                timeout = null;
            }, wait);
        }
    };
}

$(window).scroll(throttle(function() {
    var st = $(this).scrollTop();
    if (st > lastScrollTop) {
        console.log("向下滚动");
    } else {
        console.log("向上滚动");
    }
    lastScrollTop = st;
}, 100));

const observer = new IntersectionObserver(entries => {
    entries.forEach(entry => {
        if (entry.isIntersecting) {
            console.log("元素进入视口");
        } else {
            console.log("元素离开视口");
        }
    });
}, { threshold: 0.5 });

observer.observe(document.querySelector('.scroll-element'));