rem 适配

Posted 2021-09-10 freeman_Tian

// 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()
// 改变窗口大小时重新设置 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规范
            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("将根据已有的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倍的方案，其余的用1倍方案
      if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {
        dpr = 3;
      } else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)) {
        dpr = 2;
      } else {
        dpr = 1;
      }
    } else {
      // 其他设备下，仍旧使用1倍的方案
      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; // 表示1920的设计图,使用100PX的默认值
    let vW = window.innerWidth; // 当前窗口的宽度
    let vH = window.innerHeight; // 当前窗口的高度
    // 非正常屏幕下的尺寸换算
    let dueH = vW * 1080 / 1920
    if (vH < dueH) { // 当前屏幕高度小于应有的屏幕高度，就需要根据当前屏幕高度重新计算屏幕宽度
      vW = vH * 1920 /1080
    }
    let rem = vW * basePc; // 以默认比例值乘以当前窗口宽度,得到该宽度下的相应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"] = {}));