window.addEventListener('scroll', () => {
  //页面总高度
  const totalHeight = document.body.clientHeight || document.documentElement.scrollHeight;
  //当前视窗所占高度
  const viewHeight = document.documentElement.clientHeight || window.innerHeight;
  //总体可供滚动的高度
  const scrollLength = totalHeight - viewHeight;
  //当前已滚动的高度
  const scrolledHeight = document.documentElement.scrollTop || document.body.scrollTop;
  //滚动比例
  const currentProcess = scrolledHeight / scrollLength;
  console.log(currentProcess);
});