function setRem() {
  // 实际设备页面宽度和设计稿的比值
  const htmlWidth =
    document.documentElement.clientWidth || document.body.clientWidth;
  const htmlHeight =
    document.documentElement.clientHeight || document.body.clientHeight;
  const designRatio = 13680 / 2880;
  const realRatio = htmlWidth / htmlHeight;

  let baseSize = 1368;
  let scale = htmlWidth / 13680;
  document.documentElement.style.fontSize = baseSize * scale + "px";

  // 存在宽度够了，高度不够的情况
  if (realRatio > designRatio) {
    document.documentElement.style.fontSize =
      baseSize * scale * (designRatio / realRatio) + "px";
  }
}

setRem();

window.addEventListener("resize", () => {
  setRem();
});