function exec (cmd) {
return require('child_process').execSync(cmd).toString().trim()
}

const versionRequirements = [
{//对应node的版本
name: 'node',//当前环境版本，semver.clean把当前环境版本信息转化规定格式，也是' =v1.2.3 '->'1.2.3'
currentVersion: semver.clean(process.version),//要求版本，对应package.json的engines所配置的信息
versionRequirement: packageConfig.engines.node
}
]

//npm环境中
if (shell.which('npm')) {
versionRequirements.push({
name: 'npm',//执行方法得到版本号
currentVersion: exec('npm --version'),versionRequirement: packageConfig.engines.npm
})
}

module.exports = function () {
const warnings = []

for (let i = 0; i < versionRequirements.length; i++) {
const mod = versionRequirements[i]

//如果版本号不符合package.json文件中指定的版本号，就执行下面的代码
if (!semver.satisfies(mod.currentVersion,mod.versionRequirement)) {
warnings.push(mod.name + ': ' +
chalk.red(mod.currentVersion) + ' should be ' +
chalk.green(mod.versionRequirement)
)
}
}

if (warnings.length) {
console.log('')
console.log(chalk.yellow('To use this template,you must update following to modules:'))
console.log()

for (let i = 0; i < warnings.length; i++) {
const warning = warnings[i]
console.log(' ' + warning)
}

console.log()
process.exit(1)
}
}

'use strict'
const path = require('path')
const config = require('../config')
//引入extract-text-webpack-plugin插件，用来将css提取到单独的css文件中
const ExtractTextPlugin = require('extract-text-webpack-plugin')
const packageConfig = require('../package.json')

exports.assetsPath = function (_path) {
//process.env.NODE_ENV在bulid.js中定义
//如果为生产环境assetsSubDirectory为“static”，否则也为“static”
//config.build.assetsSubDirectory与config.dev.assetsSubDirectory都在config/index中定义
const assetsSubDirectory = process.env.NODE_ENV === 'production'
? config.build.assetsSubDirectory
: config.dev.assetsSubDirectory

//path.join和path.posix.join区别前者返回完整路径，后者返回完整路径的相对路径
//例：path.join是E:/shishans/blogsss/static，path.posix.join是static
return path.posix.join(assetsSubDirectory,_path)
}

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

//css-loader的基本配置
const cssLoader = {
loader: 'css-loader',options: {
//option用于配置loder的
//是否开启cssMap，默认是false
//一般我们会压缩js或者css以节省宽带,但在开发压缩就很难调试
//所以用sourceMap进行关联，给出对应的sourceMap文件
sourceMap: options.sourceMap
}
}

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

// generate loader string to be used with extract text plugin
function generateLoaders (loader,loaderOptions) {
//将上面的基础配置放到一个数据中
const loaders = options.usePostCSS ? [cssLoader,postcssLoader] : [cssLoader]
//如果该函数传递了单独的loder就加入到loaders数组中例如：sass或者less之类的
if (loader) {
loaders.push({
//加载对应的loader
loader: loader + '-loader',//es6方法Object.assign：主要用于合并对象的，浅拷贝
options: Object.assign({},loaderOptions,{
sourceMap: options.sourceMap
})
})
}

// Extract CSS when that option is specified
// (which is the case during production build)
// extract自定义属性，用ExtractTextPlugin.extract控制是否把文件单独提取
// true：单独提取，false表示不提取
if (options.extract) {
return ExtractTextPlugin.extract({
use: loaders,fallback: 'vue-style-loader'
})
} else {
//[].concat()方法用于连接数组
return ['vue-style-loader'].concat(loaders)
}
}

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

// Generate loaders for standalone style files (outside of .vue)
// 这个方法主要处理import这种方式导入的文件类型的打包
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
}

//用于返回脚手架错误的函数
exports.createNotifierCallback = () => {
//使用node-notifier来发送桌面消息,包括应用状态改变以及错误信息
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')
})
}
}

'use strict'
const path = require('path')
const utils = require('./utils')
const config = require('../config')
const vueLoaderConfig = require('./vue-loader.conf')

//获取对应文件路径的函数
//因为该文件是在项目的二级文件build下，所以要加上../这样才能找到像src这样的目录
function resolve (dir) {
//join方法用于将多个字符串结合成一个路径字符串
//path在node中会经常用到可以仔细了解一下path的各种方法
//dirname：获取当前文件所在目录的完整绝对路径
return path.join(dirname,'..',dir)
}

//eslint用来检查我们写的js代码是否满足指定的规则
const createLintingRule = () => ({
test: /.(js|vue)$/,loader: 'eslint-loader',enforce: 'pre',include: [resolve('src'),resolve('test')],options: {
formatter: require('eslint-friendly-formatter'),emitWarning: !config.dev.showEslintErrorsInOverlay
}
})

module.exports = {
context: path.resolve(__dirname,'../'),entry: {
//入口文件是src下的main.js
app: './src/main.js'
},output: {
path: config.build.assetsRoot,filename: '[name].js',publicPath: process.env.NODE_ENV === 'production'
? config.build.assetsPublicPath
: config.dev.assetsPublicPath
},resolve: {
//自动解析确定的扩展,在引入模块时不带扩展名
//例如：import somejs from "@/some"
extensions: ['.js','.vue','.json'],alias: {
// 后面的$符号指精确匹配
// 也就是说只能使用 import vuejs from "vue" 这样的方式导入vue.esm.js文件
'vue$': 'vue/dist/vue.esm.js',// resolve('src') 其实在这里就是项目根目录中的src目录
// 例如引用src目录下的some.js方法:import somejs from "@/some.js"
// 用@来代替../src
'@': resolve('src'),}
},module: {
rules: [
...(config.dev.useEslint ? [createLintingRule()] : []),{
test: /.vue$/,loader: 'vue-loader',options: vueLoaderConfig
},{
test: /.js$/,loader: 'babel-loader',resolve('test'),resolve('node_modules/webpack-dev-server/client')]
},{
test: /.(png|jpe?g|gif|svg)(\?.)?$/,loader: 'url-loader',options: {
limit: 10000,name: utils.assetsPath('img/[name].[hash:7].[ext]')
}
},{
test: /.(mp4|webm|ogg|mp3|wav|flac|aac)(\?.)?$/,name: utils.assetsPath('media/[name].[hash:7].[ext]')
}
},{
test: /.(woff2?|eot|ttf|otf)(\?.*)?$/,name: utils.assetsPath('fonts/[name].[hash:7].[ext]')
}
}
]
},node: {
// prevent webpack from injecting useless setImmediate polyfill because Vue
// source contains it (although only uses it if it's native).
setImmediate: false,// prevent webpack from injecting mocks to Node native modules
// that does not make sense for the client
dgram: 'empty',fs: 'empty',net: 'empty',tls: 'empty',child_process: 'empty'
}
}

const HOST = process.env.HOST
const PORT = process.env.PORT && Number(process.env.PORT)

const devWebpackConfig = merge(baseWebpackConfig,{
module: {
rules: utils.styleLoaders({ sourceMap: config.dev.cssSourceMap,usePostCSS: true })
},// cheap-module-eval-source-map is faster for development
// devtool是开发工具选项，用来指定如何生成sourcemap文件，cheap-module-eval-source-map此款soucemap文件性价比最高
// 生产环境：#source-map
// 开发环境：#cheap-module-eval-source-map 编译消耗小
devtool: config.dev.devtool,// these devServer options should be customized in /config/index.js
devServer: {
clientLogLevel: 'warning',historyApiFallback: {
rewrites: [
{ from: /./,to: path.posix.join(config.dev.assetsPublicPath,'index.html') },],},hot: true,contentBase: false,// since we use CopyWebpackPlugin.
compress: true,host: HOST || config.dev.host,port: PORT || config.dev.port,open: config.dev.autoOpenBrowser,overlay: config.dev.errorOverlay
? { warnings: false,errors: true }
: false,publicPath: config.dev.assetsPublicPath,proxy: config.dev.proxyTable,quiet: true,// necessary for FriendlyErrorsPlugin
watchOptions: {
poll: config.dev.poll,plugins: [
// DefinePlugin内置webpack插件，专门用来定义全局变量的
// 下面定义一个全局变量 process.env 并且值是如下
new webpack.DefinePlugin({
'process.env': require('../config/dev.env')
}),// 这个插件帮助你实现无刷新加载，关于内部实现原理
new webpack.HotModuleReplacementPlugin(),new webpack.NamedModulesPlugin(),// HMR shows correct file names in console on update.
new webpack.NoEmitOnErrorsPlugin(),// https://github.com/ampedandwired/html-webpack-plugin
new HtmlWebpackPlugin({
filename: 'index.html',template: 'index.html',inject: true
}),// copy custom static assets
new CopyWebpackPlugin([
{
from: path.resolve(__dirname,'../static'),to: config.dev.assetsSubDirectory,ignore: ['.']
}
])
]
})

module.exports = new Promise((resolve,reject) => {
portfinder.basePort = process.env.PORT || config.dev.port
portfinder.getPort((err,port) => {
if (err) {
reject(err)
} else {
// publish the new Port,necessary for e2e tests
process.env.PORT = port
// add port to devServer config
devWebpackConfig.devServer.port = port

// Add FriendlyErrorsPlugin
devWebpackConfig.plugins.push(new FriendlyErrorsPlugin({
compilationSuccessInfo: {
messages: [Your application is running here: http://${devWebpackConfig.devServer.host}:${port}],onErrors: config.dev.notifyOnErrors
? utils.createNotifierCallback()
: undefined
}))

resolve(devWebpackConfig)
}
})
})