详解vue项目中如何引入全局sass/less变量、function、mixin

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。

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