原生js实现判断浏览器滚动条向上滚动还是向下滚动，实时监听浏览器的滚动方向

// 监听浏览器的滚动事件 判断是向上滚动还是向下滚动
var lastScrollTop = 0;
window.addEventListener("scroll", function () {
    var scrollTop = window.pageYOffset || document.documentElement.scrollTop;
    if (scrollTop > lastScrollTop) {
        console.log('向下滚动')
    } else {
        console.log('向上滚动')
    }
    lastScrollTop = scrollTop;
});