window.onscroll = percent; // 执行函数
// 页面百分比
function percent() {
  let a = document.documentElement.scrollTop || window.pageYOffset, // 卷去高度
    b =
      Math.max(
        document.body.scrollHeight,
        document.documentElement.scrollHeight,
        document.body.offsetHeight,
        document.documentElement.offsetHeight,
        document.body.clientHeight,
        document.documentElement.clientHeight
      ) - document.documentElement.clientHeight, // 整个网页高度
    result = Math.round((a / b) * 100), // 计算百分比
    up = document.querySelector("#go-up"); // 获取按钮

  if (result <= 95) {
    up.childNodes[0].style.display = "none";
    up.childNodes[1].style.display = "block";
    up.childNodes[1].innerHTML = result;
  } else {
    up.childNodes[1].style.display = "none";
    up.childNodes[0].style.display = "block";
  }
}