GoTop

gotop.js

function goTop (acc, t) {
  const acceleration = acc || 0.1
  const time = t || 16

  const document = window.document

  let x1 = 0
  let y1 = 0
  let x2 = 0
  let y2 = 0

  if (document.documentElement) {
    x1 = document.documentElement.scrollLeft || 0;
    y1 = document.documentElement.scrollTop || 0;
  }
  if (document.body) {
    x2 = document.body.scrollLeft || 0;
    y2 = document.body.scrollTop || 0;
  }
  const x3 = window.scrollX || 0;
  const y3 = window.scrollY || 0;

  // 滚动条到页面顶部的水平距离
  const x = Math.max(x1, Math.max(x2, x3));
  // 滚动条到页面顶部的垂直距离
  const y = Math.max(y1, Math.max(y2, y3));

  // 滚动距离 = 目前距离 / 速度, 因为距离原来越小, 速度是大于 1 的数, 所以滚动距离会越来越小
  const speed = 1 + acceleration;
  window.scrollTo(Math.floor(x / speed), Math.floor(y / speed));

  // 如果距离不为零, 继续调用迭代本函数
  if(x > 0 || y > 0) {
    window.setTimeout(goTop, time);
  }
  return
}