vue - utils.js

exports:导出功能函数或变量

module.exports:默认导出{}

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module.exports 初始值为一个空对象 {}

exports 是指向的 module.exports 的引用

require() 返回的是 module.exports 而不是 exports

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关于module.exports和exports.js详情请查看：https://cnodejs.org/topic/5231a630101e574521e45ef8

 'use strict'
 // 路径
 const path = require('path')
 // 来自config/index.js
 const config = require('../config')

 const ExtractTextPlugin = require('extract-text-webpack-plugin')
 // 来自package.json
 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
     }
   }

   const postcssLoader = {
     loader: 'postcss-loader',
     options: {
       sourceMap: options.sourceMap
     }
   }

   // 生成与extract文本插件一起使用的加载器字符串
   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
         })
       })
     }

     //指定该选项时提取CSS
     //（在生产构建期间就是这种情况）
     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')
   }
 }

 // 为单独样式文件生成加载器（.vue之外）
 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')
     })
   }
 }