关于javascript:rem-适配

// 基准大小
const baseSize = 50

export function getClientW() {
    let htmlWidth = document.documentElement.clientWidth || document.body.clientWidth;
    if (htmlWidth > 768) {htmlWidth = 768}
    if (htmlWidth < 320) {htmlWidth = 320}
    // console.log(htmlWidth);

    return htmlWidth
}


// 计算根节点 字体大小  自适应  remy
function setRem(normalWidth = 375) {const size = getClientW() / normalWidth * baseSize
    document.body.style.fontSize = size + 'px'
    let htmlDom = document.getElementsByTagName('html')[0]
    htmlDom.style.fontSize = size + 'px'
    return size
}
// 初始化
setRem()
// 扭转窗口大小时从新设置 rem
window.onresize = function () {setRem()
};

//Android 微信中，借助 WeixinJSBridge 对象来阻止字体大小调整
(function () {if (typeof WeixinJSBridge == "object" && typeof WeixinJSBridge.invoke == "function") {handleFontSize();
    } else {if (document.addEventListener) {document.addEventListener("WeixinJSBridgeReady", handleFontSize, false);
        } else if (document.attachEvent) {
            //IE 浏览器，非 W3C 标准
            document.attachEvent("onWeixinJSBridgeReady", handleFontSize);
        }
    }

    function handleFontSize() {
        // 设置网页字体为默认大小
        WeixinJSBridge.invoke('setFontSizeCallback', {'fontSize': 0});
        // 重写设置网页字体大小的事件
        WeixinJSBridge.on('menu:setfont', function () {
            WeixinJSBridge.invoke('setFontSizeCallback', {'fontSize': 0});
        });
    }
})();

(function(win, lib) {
  var doc = win.document;
  var docEl = doc.documentElement;
  var metaEl = doc.querySelector('meta[name="viewport"]');
  var flexibleEl = doc.querySelector('meta[name="flexible"]');
  var dpr = 0;
  var scale = 0;
  var tid;
  var flexible = lib.flexible || (lib.flexible = {});

  if (metaEl) {console.warn("将依据已有的 meta 标签来设置缩放比例");
    var match = metaEl
      .getAttribute("content")
      // eslint-disable-next-line no-useless-escape
      .match(/initial\-scale=([\d\.]+)/);
    if (match) {scale = parseFloat(match[1]);
      dpr = parseInt(1 / scale);
    }
  } else if (flexibleEl) {var content = flexibleEl.getAttribute("content");
    if (content) {
      // eslint-disable-next-line no-useless-escape
      var initialDpr = content.match(/initial\-dpr=([\d\.]+)/);
      // eslint-disable-next-line no-useless-escape
      var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/);
      if (initialDpr) {dpr = parseFloat(initialDpr[1]);
        scale = parseFloat((1 / dpr).toFixed(2));
      }
      if (maximumDpr) {dpr = parseFloat(maximumDpr[1]);
        scale = parseFloat((1 / dpr).toFixed(2));
      }
    }
  }

  if (!dpr && !scale) {
    // eslint-disable-next-line no-unused-vars
    var isAndroid = win.navigator.appVersion.match(/android/gi);
    var isIPhone = win.navigator.appVersion.match(/iphone/gi);
    var devicePixelRatio = win.devicePixelRatio;
    if (isIPhone) {
      // iOS 下，对于 2 和 3 的屏，用 2 倍的计划，其余的用 1 倍计划
      if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {dpr = 3;} else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)) {dpr = 2;} else {dpr = 1;}
    } else {
      // 其余设施下，仍旧应用 1 倍的计划
      dpr = 1;
    }
    scale = 1 / dpr;
  }

  docEl.setAttribute("data-dpr", dpr);
  if (!metaEl) {metaEl = doc.createElement("meta");
    metaEl.setAttribute("name", "viewport");
    metaEl.setAttribute(
      "content",
      "initial-scale=" +
        scale +
        ", maximum-scale=" +
        scale +
        ", minimum-scale=" +
        scale +
        ", user-scalable=no"
    );
    if (docEl.firstElementChild) {docEl.firstElementChild.appendChild(metaEl);
    } else {var wrap = doc.createElement("div");
      wrap.appendChild(metaEl);
      doc.write(wrap.innerHTML);
    }
  }

  // function refreshRem() {//   var width = docEl.getBoundingClientRect().width;
  //   // 最小 1366px，最大适配 2560px
  //   if (width / dpr < 1366) {
  //     width = 1366 * dpr;
  //   } else if (width / dpr > 2560) {
  //     width = 2560 * dpr;
  //   }
  //   // 设置成 24 等份，设计稿时 1920px 的，这样 1rem 就是 80px
  //   var rem = width / 24;
  //   docEl.style.fontSize = rem + "px";
  //   flexible.rem = win.rem = rem;
  // }

  function refreshRem() {
    var baseSize = 100;
    let basePc = baseSize / 1920; // 示意 1920 的设计图, 应用 100PX 的默认值
    let vW = window.innerWidth; // 以后窗口的宽度
    let vH = window.innerHeight; // 以后窗口的高度
    // 非正常屏幕下的尺寸换算
    let dueH = vW * 1080 / 1920
    if (vH < dueH) { // 以后屏幕高度小于应有的屏幕高度，就须要依据以后屏幕高度从新计算屏幕宽度
      vW = vH * 1920 /1080
    }
    let rem = vW * basePc; // 以默认比例值乘以以后窗口宽度, 失去该宽度下的相应 font-size 值
    document.documentElement.style.fontSize =  rem + "px";
    flexible.rem = win.rem = rem;
  }

  win.addEventListener(
    "resize",
    function() {clearTimeout(tid);
      tid = setTimeout(refreshRem, 300);
    },
    false
  );
  win.addEventListener(
    "pageshow",
    function(e) {if (e.persisted) {clearTimeout(tid);
        tid = setTimeout(refreshRem, 300);
      }
    },
    false
  );

  if (doc.readyState === "complete") {doc.body.style.fontSize = 12 * dpr + "px";} else {
    doc.addEventListener(
      "DOMContentLoaded",
      // eslint-disable-next-line no-unused-vars
      function(e) {doc.body.style.fontSize = 12 * dpr + "px";},
      false
    );
  }

  refreshRem();

  flexible.dpr = win.dpr = dpr;
  flexible.refreshRem = refreshRem;
  flexible.rem2px = function(d) {var val = parseFloat(d) * this.rem;
    if (typeof d === "string" && d.match(/rem$/)) {val += "px";}
    return val;
  };
  flexible.px2rem = function(d) {var val = parseFloat(d) / this.rem;
    if (typeof d === "string" && d.match(/px$/)) {val += "rem";}
    return val;
  };
})(window, window["lib"] || (window["lib"] = {}));