摘要：下載或在項(xiàng)目中引入一般情況在中引入設(shè)置標(biāo)簽視情況而定安裝或在中配置，在項(xiàng)目文件中找到，將添加到中，，下的根據(jù)設(shè)計(jì)稿而定具體如下編譯新加由于設(shè)計(jì)稿是添加到里面省略項(xiàng)目中使用假設(shè)設(shè)計(jì)稿和分別是，具體代碼

1.下載lib-flexible

npm i lib-flexible --save
或
yarn add lib-flexible

2.在項(xiàng)目中引入lib-flexible 一般情況在(main.js中引入lib-flexible)

import "lib-flexible/flexible"

3.設(shè)置meta標(biāo)簽(視情況而定)

4.安裝px2rem-loader

npm install px2rem-loader   --save
或
yarn add px2rem-loader

5.在webpack中配置px2rem-loader

1，在項(xiàng)目build文件中找到util.js，將px2rem-loader添加到cssLoaders中，
2，px2rem-loader 下的 remUnit 根據(jù)設(shè)計(jì)稿而定
具體如下：

exports.cssLoaders = function (options) {
  options = options || {}

  const cssLoader = {
    loader: "css-loader",
    options: {
      minimize: process.env.NODE_ENV === "production",
      sourceMap: options.sourceMap
    }
  }
  //rem編譯（新加px2）
  const px2remLoader = {
    loader: "px2rem-loader",
    options: {
      remUnit: 75 // 由于設(shè)計(jì)稿是750
    }
  }

  function generateLoaders (loader, loaderOptions) {
    var loaders = [cssLoader,px2remLoader]//添加到loader里面
    省略.....
  }
}

6.項(xiàng)目中使用

假設(shè)設(shè)計(jì)稿width和font-size分別是200px，50px
具體代碼：(按照設(shè)計(jì)稿寫即可)

.demo{
    width: 200px;
    font-size: 50px;
}

7.多帶帶使用flexible可直接添加一個(gè)rem.js文件，具體如下：

1，配合less，sass和stylus來(lái)做px轉(zhuǎn)換rem
2，具體可參看css編譯

/*
** 移動(dòng)端自適應(yīng)方案  FROM 手淘
*/
export const setViewport = (()=>{//此處是多帶帶使用
    const win = window
    const lib = window.lib || (window.lib = {})
//;(function(win, lib) {//此處是直接使用
    let doc = win.document;
    let docEl = doc.documentElement;
    let metaEl = doc.querySelector("meta[name="viewport"]");
    let flexibleEl = doc.querySelector("meta[name="flexible"]");
    let dpr = 0;
    let scale = 0;
    let tid;
    let flexible = lib.flexible || (lib.flexible = {});
    
    if (metaEl) {
        //console.warn("將根據(jù)已有的meta標(biāo)簽來(lái)設(shè)置縮放比例");
        let match = metaEl.getAttribute("content").match(/initial-scale=([d.]+)/);
        if (match) {
            scale = parseFloat(match[1]);
            dpr = parseInt(1 / scale);
        }
    } else if (flexibleEl) {
        let content = flexibleEl.getAttribute("content");
        if (content) {
            let initialDpr = content.match(/initial-dpr=([d.]+)/);
            let 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) {
        //let isAndroid = win.navigator.appVersion.match(/android/gi);
        let isIPhone = win.navigator.appVersion.match(/iphone/gi);
        let devicePixelRatio = win.devicePixelRatio;
        if (isIPhone) {
            // iOS下，對(duì)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 {
            // 其他設(shè)備下，仍舊使用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 {
            let wrap = doc.createElement("div");
            wrap.appendChild(metaEl);
            doc.write(wrap.innerHTML);
        }
    }

    function refreshRem(){
        let width = docEl.getBoundingClientRect().width;
        if (width / dpr > 540) {
            width = 540 * dpr;
        }
        let rem = width / 10;
        docEl.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", function() {
            doc.body.style.fontSize = 12 * dpr + "px";
        }, false);
    }

    refreshRem();

    flexible.dpr = win.dpr = dpr;
    flexible.refreshRem = refreshRem;
    flexible.rem2px = function(d) {
        let val = parseFloat(d) * this.rem;
        if (typeof d === "string" && d.match(/rem$/)) {
            val += "px";
        }
        return val;
    };
    flexible.px2rem = function(d) {
        let val = parseFloat(d) / this.rem;
        if (typeof d === "string" && d.match(/px$/)) {
            val += "rem";
        }
        return val;
    };

});
//})(window, window.lib || (window.lib = {}));