h5移动端rem使用750设计稿

<script>
      function getFontSize() {
        var baseFontSize = 100;
        var baseWidth = 750;
        var minWidth = 320;
        var clientWidth = window.innerWidth;
        var innerWidth = Math.max(Math.min(clientWidth, baseWidth), minWidth);
        var rem = clientWidth / (baseWidth / baseFontSize);
        if (clientWidth > baseWidth) {
          rem = 100;
        }
        if (clientWidth < minWidth) {
          rem = minWidth / (baseWidth / baseFontSize);
        }
        document.querySelector("html").style.fontSize = rem + "px";
      }
      (function (doc, win) {
        getFontSize();
        window.onresize = function () {
          getFontSize();
        };
      })(document, window);
</script>