JavaScript判断页面滚动方向的三种方法

window.addeventlistener('scroll', function() {
  const currentscroll = window.pageyoffset || document.documentelement.scrolltop;
  
  if (currentscroll > lastscrolltop) {
    // 向下滚动
    console.log('向下滚动');
  } else if (currentscroll < lastscrolltop) {
    // 向上滚动
    console.log('向上滚动');
  }
  
  lastscrolltop = currentscroll <= 0 ? 0 : currentscroll;
}, false);

window.addeventlistener('scroll', function() {
  const currentscrollposition = window.pageyoffset;
  const scrolldelta = currentscrollposition - lastscrollposition;
  
  if (scrolldelta > 0) {
    console.log('向下滚动', scrolldelta);
  } else if (scrolldelta < 0) {
    console.log('向上滚动', scrolldelta);
  }
  
  lastscrollposition = currentscrollposition;
});

let ticking = false;

window.addeventlistener('scroll', function() {
  lastknownscrollposition = window.scrolly;
  
  if (!ticking) {
    window.requestanimationframe(function() {
      const current = lastknownscrollposition;
      const direction = current > (lastknownscrollposition || 0) ? 'down' : 'up';
      console.log(direction);
      ticking = false;
    });
    
    ticking = true;
  }
});

// 获得滚动的像素数
const intelemscrolltop = element.scrolltop;

// 设置滚动的距离
element.scrolltop = intvalue;

window.pageyoffset === window.scrolly; // true

const usescrolltop = () => {
  return window.pageyoffset || document.documentelement.scrolltop || document.body.scrolltop || 0;
}