让我们考虑下场景:当使用rem/vw开发移动端的时候，你定义了一个px转rem的函数,或者是网站配色的全局变量等，然后到工程里为每个vue文件或者组件@import ‘publicfilename.scss’,那得重复做这样的工作很多很多…次，万一这些公用文件目录路径变怎么办呢，哭都来不及，想想都觉得恐怖呀！

接下来拯救我们的神器就要登场了—sass-resources-loader,它可以省去重复性的引入，还支持less,postcss等，具体用法如下：

 npm install -d sass-resource-loader

• 首先我们找到项目里build目录，在该目录下找到util.js
  更新前util.js代码如下:

'use strict'
const path = require('path')
const config = require('../config')
const ExtractTextPlugin = require('extract-text-webpack-plugin')
const packageConfig = require('../package.json')
exports.assetsPath = function (_path) {
  const assetsSubDirectory = process.env.NODE_ENV === 'production'
    ? config.build.assetsSubDirectory
    : config.dev.assetsSubDirectory

  return path.posix.join(assetsSubDirectory, _path)
}

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

  const cssLoader = {
    loader: 'css-loader',
    options: {
      sourceMap: options.sourceMap
    }
  }

  // generate loader string to be used with extract text plugin
  function generateLoaders (loader, loaderOptions) {
    const loaders = options.usePostCSS ? [cssLoader, postcssLoader] : [cssLoader]

    if (loader) {
      loaders.push({
        loader: loader + '-loader',
        options: Object.assign({}, loaderOptions, {
          sourceMap: options.sourceMap
        })
      })
    }

    // Extract CSS when that option is specified
    // (which is the case during production build)
    if (options.extract) {
      return ExtractTextPlugin.extract({
        use: loaders,
        fallback: 'vue-style-loader'
      })
    } else {
      return ['vue-style-loader'].concat(loaders)
    }
  }

  // https://vue-loader.vuejs.org/en/configurations/extract-css.html
  return {
    css: generateLoaders(),
    postcss: generateLoaders(),
    less: generateLoaders('less'),
    sass: generateLoaders('sass', { indentedSyntax: true }),
    scss: generateLoaders('sass'),
    stylus: generateLoaders('stylus'),
    styl: generateLoaders('stylus')
  }
}

// Generate loaders for standalone style files (outside of .vue)
exports.styleLoaders = function (options) {
  const output = []
  const loaders = exports.cssLoaders(options)

  for (const extension in loaders) {
    const loader = loaders[extension]
    output.push({
      test: new RegExp('\\.' + extension + '$'),
      use: loader
    })
  }

  return output
}

exports.createNotifierCallback = () => {
  const notifier = require('node-notifier')

  return (severity, errors) => {
    if (severity !== 'error') return

    const error = errors[0]
    const filename = error.file && error.file.split('!').pop()

    notifier.notify({
      title: packageConfig.name,
      message: severity + ': ' + error.name,
      subtitle: filename || '',
      icon: path.join(__dirname, 'logo.png')
    })
  }
}

/**
 * 增加 hljs 的 classname
 */
exports.wrapCustomClass = function (render) {
  return function (...args) {
    return render(...args)
      .replace('<code class="', '<code class="hljs ')
      .replace('<code>', '<code class="hljs">')
  }
}
/**
 * Format HTML string
 */
exports.convertHtml = function (str) {
  return str.replace(/(&#x)(\w{4});/gi, $0 => String.fromCharCode(parseInt(encodeURIComponent($0).replace(/(%26%23x)(\w{4})(%3B)/g, '$2'), 16)))
}

看util.js文件，我们首先找到我需要修改目标在哪：

// https://vue-loader.vuejs.org/en/configurations/extract-css.html
  return {
    css: generateLoaders(),
    postcss: generateLoaders(),
    less: generateLoaders('less'),
    sass: generateLoaders('sass', { indentedSyntax: true }),
    scss: generateLoaders('sass'),
    stylus: generateLoaders('stylus'),
    styl: generateLoaders('stylus')
  }

我们那sass为例，用sass-resources-loader对其改造：

/**
   * sass Less 源文件
   * @param name classFile
   * @returns {string}
   */
  function resolveResouce(name) {
    return path.resolve(__dirname, '../static/' + name);
  }

  //导入全局sass mixin function等
  function generateSassResourceLoader(){
    var loaders = [
      cssLoader,
      //'postcss-loader',
      'sass-loader',
      {
        loader:'sass-resources-loader',
        options: {
          //需要一个全局路径
          resources: [resolveResouce('index.scss')]
        }
      }
    ]
    if(options.extract){
      return ExtractTextPlugin.extract({
        use:loaders,
        fallback: 'vue-style-loader'
      })
    }else{
      return ['vue-style-loader'].concat(loaders)
    }
  }

工具写好好了，接下来直接把上门return对象做些调整，代码如下

  // https://vue-loader.vuejs.org/en/configurations/extract-css.html
  return {
    css: generateLoaders(),
    postcss: generateLoaders(),
    less: generateLoaders('less'),
    sass:generateSassResourceLoader(),
    scss:generateSassResourceLoader(),
    stylus: generateLoaders('stylus'),
    styl: generateLoaders('stylus')
  }

从代码中可以看出，我们把sass和scss的loader换成我们自己根据sass-resources-loader写的方法了，这样就实现了我们的目标。