vue項目中一些文件的做用

原文

　　簡書原文：https://www.jianshu.com/p/38749e5bec3c

大綱

　　一、vue項目結構
　　二、主要的配置文件
　　2.一、package.json
　　2.二、dev-server.js
　　2.三、webpack.base.conf.js
　　2.四、webpack.dev.conf.js
　　2.五、build.js
　　2.六、webpack.prod.conf.js
　　2.七、config/index.js

一、vue項目結構

/*
├── build --------------------------------- webpack相關配置文件
│   ├── build.js --------------------------webpack打包配置文件
│   ├── check-versions.js ------------------------------ 檢查npm,nodejs版本
│   ├── dev-client.js ---------------------------------- 設置環境
│   ├── dev-server.js ---------------------------------- 建立express服務器，配置中間件，啓動可熱重載的服務器，用於開發項目
│   ├── utils.js --------------------------------------- 配置資源路徑，配置css加載器
│   ├── vue-loader.conf.js ----------------------------- 配置css加載器等
│   ├── webpack.base.conf.js --------------------------- webpack基本配置
│   ├── webpack.dev.conf.js ---------------------------- 用於開發的webpack設置
│   ├── webpack.prod.conf.js --------------------------- 用於打包的webpack設置
├── config ---------------------------------- 配置文件
├── node_modules ---------------------------- 存放依賴的目錄
├── src ------------------------------------- 源碼
│   ├── assets ------------------------------ 靜態文件
│   ├── components -------------------------- 組件 
│   ├── main.js ----------------------------- 主js
│   ├── App.vue ----------------------------- 項目入口組件
│   ├── router ------------------------------ 路由
├── package.json ---------------------------- node配置文件
├── .babelrc--------------------------------- babel配置文件
├── .editorconfig---------------------------- 編輯器配置
├── .gitignore------------------------------- 配置git可忽略的文件
*/

二、主要的配置文件

2.一、package.json

/*
  首選來看一下package.json裏面scripts字段，看一下在執行npm run dev 和
npm run build時作了什麼
*/
"name": "wheelsfactory",
"version": "1.0.0",
"description": "this is a demo",
"scripts": {
    "dev": "node build/dev-server.js",
    "start": "node build/dev-server.js",
    "build": "node build/build.js"
}

/*
    當咱們執行npm run dev時，首選執行的是dev-server.js
    當咱們執行npm run build時，首選執行的是build.js
*/

2.二、dev-server.js

/*
    一、引入配置文件
    二、引入相關插件
    三、建立express實例
    四、配置webpack-dev-middleware和webpack-hot-middleware
    五、配置靜態資源路徑，並掛到express服務上
    六、啓動服務器，並判斷是否自動打開默認瀏覽器
    七、監聽端口
*/
require('./check-versions')()
//引入相關配置
var config = require('../config')
// 檢查Node的環境變量，若是沒有則使用配置文件中設置的環境
if (!process.env.NODE_ENV) {
  process.env.NODE_ENV = JSON.parse(config.dev.env.NODE_ENV)
}
 
//opn -- A better node-open. Opens stuff like websites, files, executables. Cross-platform.
//這裏用來打開默認瀏覽器，打開dev-server監聽的端口
var opn = require('opn')
var path = require('path')
var express = require('express')
var webpack = require('webpack')
//express中間件，用於http請求代理到其餘服務器
var proxyMiddleware = require('http-proxy-middleware')
//判斷當前環境，選擇導入的webpack配置
var webpackConfig = process.env.NODE_ENV === 'testing'
  ? require('./webpack.prod.conf')
  : require('./webpack.dev.conf')

// default port where dev server listens for incoming traffic
//默認的dev-server的監聽端口
var port = process.env.PORT || config.dev.port
// automatically open browser, if not set will be false
//是否自動打開瀏覽器，默認是false
var autoOpenBrowser = !!config.dev.autoOpenBrowser
// Define HTTP proxies to your custom API backend
// https://github.com/chimurai/http-proxy-middleware
//定義http代理到你的自定義的API後端
var proxyTable = config.dev.proxyTable
//建立express實例
var app = express()
// 根據webpack的config建立Compiler對象
var compiler = webpack(webpackConfig)

//使用compiler相應的文件進行編譯和綁定，編譯後的內容將存放在內存中
var devMiddleware = require('webpack-dev-middleware')(compiler, {
  publicPath: webpackConfig.output.publicPath,
  quiet: true
})
//用於實現熱重載
var hotMiddleware = require('webpack-hot-middleware')(compiler, {
  log: false,
  heartbeat: 2000
})
// force page reload when html-webpack-plugin template changes
//當html-webpack-plugin提交頁面以後，使用熱重載強制頁面重載
compiler.plugin('compilation', function (compilation) {
  compilation.plugin('html-webpack-plugin-after-emit', function (data, cb) {
    hotMiddleware.publish({ action: 'reload' })
    cb()
  })
})

// proxy api requests
//在express上使用代理表中的配置
Object.keys(proxyTable).forEach(function (context) {
  var options = proxyTable[context]
  if (typeof options === 'string') {
    options = { target: options }
  }
  app.use(proxyMiddleware(options.filter || context, options))
})

// handle fallback for HTML5 history API
//一個解決單頁的重定向錯誤的插件
app.use(require('connect-history-api-fallback')())

// serve webpack bundle output
// 使用devMiddleware，webpack編譯後的文件將掛到express服務器上
app.use(devMiddleware)

// enable hot-reload and state-preserving
// compilation error display
// 使用熱重載中間件
app.use(hotMiddleware)

// serve pure static assets
//配置靜態資源路徑
var staticPath = path.posix.join(config.dev.assetsPublicPath, config.dev.assetsSubDirectory)
//將靜態文件掛到express服務器上
app.use(staticPath, express.static('./static'))
//設置應用的url
var uri = 'http://localhost:' + port

var _resolve
var readyPromise = new Promise(resolve => {
  _resolve = resolve
})

console.log('> Starting dev server...')
//devMiddleware valid以後，啓動服務
devMiddleware.waitUntilValid(() => {
  console.log('> Listening at ' + uri + '\n')
  // when env is testing, don't need open it
  //若是設置爲自動打開瀏覽器，經過opn打開uri
  if (autoOpenBrowser && process.env.NODE_ENV !== 'testing') {
    opn(uri)
  }
  _resolve()
})
//監聽配置的端口
var server = app.listen(port)

module.exports = {
  ready: readyPromise,
  close: () => {
    server.close()
  }
}

2.三、webpack.base.conf.js

/*
    一、配置編譯入口和輸出路徑
    二、模塊resolve的規則
    三、配置不一樣類型模塊的處理規則
*/
var path = require('path')
var utils = require('./utils')
var config = require('../config')
var vueLoaderConfig = require('./vue-loader.conf')
//絕對路徑
function resolve (dir) {
  return path.join(__dirname, '..', dir)
}

module.exports = {
  //webpack的入口文件
  entry: {
    app: './src/main.js'
  },
  output: {
     //webpack輸出文件的路徑
    path: config.build.assetsRoot,
    //輸出的文件命名格式
    filename: '[name].js',
    // webpack編譯輸出的發佈路徑
    publicPath: process.env.NODE_ENV === 'production'
      ? config.build.assetsPublicPath
      : config.dev.assetsPublicPath
  },
  //模塊resolve的規則
  resolve: {
    //resolve的後綴名
    extensions: ['.js', '.vue', '.json'],
    //配置路徑別名，好比import Vue from 'vue/dist/vue.common.js'--> import Vue from 'vue'
    alias: {
      'vue$': 'vue/dist/vue.esm.js',
      '@': resolve('src')
    }
  },
  //配置不一樣類型模塊的處理規則
  module: {
    rules: [
    // src和test文件夾下的.js和.vue文件使用eslint-loader
      {
        test: /\.(js|vue)$/,
        loader: 'eslint-loader',
        enforce: 'pre',
        include: [resolve('src'), resolve('test')],
        options: {
          formatter: require('eslint-friendly-formatter')
        }
      },
      //全部的.vue文件使用vue-loader
      {
        test: /\.vue$/,
        loader: 'vue-loader',
        options: vueLoaderConfig
      },
      //src和test下的.js文件使用babel-loader
      {
        test: /\.js$/,
        loader: 'babel-loader',
        include: [resolve('src'), resolve('test')]
      },
      //全部的圖片文件使用url-loader
      {
        test: /\.(png|jpe?g|gif|svg)(\?.*)?$/,
        loader: 'url-loader',
        options: {
          limit: 10000,
          name: utils.assetsPath('img/[name].[hash:7].[ext]')
        }
      },
      //全部的音頻文件使用url-loader
      {
        test: /\.(mp4|webm|ogg|mp3|wav|flac|aac)(\?.*)?$/,
        loader: 'url-loader',
        options: {
          limit: 10000,
          name: utils.assetsPath('media/[name].[hash:7].[ext]')
        }
      },
      //全部的字體文件使用url-loader
      {
        test: /\.(woff2?|eot|ttf|otf)(\?.*)?$/,
        loader: 'url-loader',
        options: {
          limit: 10000,
          name: utils.assetsPath('fonts/[name].[hash:7].[ext]')
        }
      }
    ]
  }
}

2.四、webpack.dev.conf.js

/*
    一、合併基礎的webpack配置
    二、使用styleLoaders
    三、配置Source Maps
    四、配置webpack插件
*/
var utils = require('./utils')
var webpack = require('webpack')
var config = require('../config')
var merge = require('webpack-merge')
var baseWebpackConfig = require('./webpack.base.conf')
//生成html文件並自動注入依賴文件的插件， script & link
var HtmlWebpackPlugin = require('html-webpack-plugin')
//一個輸出webpack警告，錯誤的插件
var FriendlyErrorsPlugin = require('friendly-errors-webpack-plugin')

// add hot-reload related code to entry chunks
//添加熱重載相關的代碼到entry chunks
Object.keys(baseWebpackConfig.entry).forEach(function (name) {
  baseWebpackConfig.entry[name] = ['./build/dev-client'].concat(baseWebpackConfig.entry[name])
})
//合併webpack.base.conf
module.exports = merge(baseWebpackConfig, {
  module: {
    //使用styleLoaders處理樣式文件
    rules: utils.styleLoaders({ sourceMap: config.dev.cssSourceMap })
  },
  // cheap-module-eval-source-map is faster for development
  //配置Source Maps

  devtool: '#cheap-module-eval-source-map',
  //配置webpack插件
  plugins: [
    new webpack.DefinePlugin({
      'process.env': config.dev.env
    }),
    // https://github.com/glenjamin/webpack-hot-middleware#installation--usage
    new webpack.HotModuleReplacementPlugin(),
    //在編譯出現錯誤時，使用 NoEmitOnErrorsPlugin 來跳過輸出階段。這樣能夠確保輸出資源不會包含錯誤。
    new webpack.NoEmitOnErrorsPlugin(),
    // https://github.com/ampedandwired/html-webpack-plugin
    new HtmlWebpackPlugin({
      filename: 'index.html',
      template: 'index.html',
      inject: true
    }),
    new FriendlyErrorsPlugin()
  ]
})

>/** 配置Source Maps
/*
    一、source-map 在一個單獨的文件中產生一個完整且功能徹底的文件。這個文件具備最
好的source map，可是它會減慢打包文件的構建速度；

    二、cheap-module-source-map在一個單獨的文件中生成一個不帶列映射的map，不帶列
映射提升項目構建速度，可是也使得瀏覽器開發者工具只能對應到具體的行，不能對應
到具體的列（符號），會對調試形成不便；

    三、eval-source-map 使用eval打包源文件模塊，在同一個文件中生成乾淨的完整的
source map。這個選項能夠在不影響構建速度的前提下生成完整的sourcemap，可是對打包後
輸出的JS文件的執行具備性能和安全的隱患。不過在開發階段這是一個很是好的選項，可是在
生產階段必定不要用這個選項；

    四、cheap-module-eval-source-map 這是在打包文件時最快的生成source map的方法，
生成的Source Map 會和打包後的JavaScript文件同行顯示，沒有列映射，和eval-source-map
選項具備類似的缺點；
*/

2.五、build.js

/*
    一、webpack編譯
    二、輸出信息
*/

require('./check-versions')()
process.env.NODE_ENV = 'production'
//控制檯loading動畫
var ora = require('ora')
var rm = require('rimraf')
var path = require('path')
// 高亮控制檯輸出的插件
var chalk = require('chalk')
var webpack = require('webpack')
var config = require('../config')
var webpackConfig = require('./webpack.prod.conf')
//在控制檯輸出building for production...
var spinner = ora('building for production...')
//開始loading動畫
spinner.start()
//獲取輸出文件路徑
rm(path.join(config.build.assetsRoot, config.build.assetsSubDirectory), err => {
  if (err) throw err
  //webpack編譯  
  webpack(webpackConfig, function (err, stats) {
    //中止loading動畫
    spinner.stop()
    //若是錯誤拋出錯誤
    if (err) throw err
    //完成輸出相關信息 
    process.stdout.write(stats.toString({
      colors: true,
      modules: false,
      children: false,
      chunks: false,
      chunkModules: false
    }) + '\n\n')

    console.log(chalk.cyan('  Build complete.\n'))
    console.log(chalk.yellow(
      '  Tip: built files are meant to be served over an HTTP server.\n' +
      '  Opening index.html over file:// won\'t work.\n'
    ))
  })
})

2.六、webpack.prod.conf.js

/*
    一、合併基礎的webpack配置
    二、配置webpack的輸出
    三、配置webpack插件
    四、配置gzip模式
    五、配置webpack-bundle-analyzer，分析打包後生成的文件結構
*/

var path = require('path')
var utils = require('./utils')
var webpack = require('webpack')
var config = require('../config')
var merge = require('webpack-merge')
var baseWebpackConfig = require('./webpack.base.conf')
var CopyWebpackPlugin = require('copy-webpack-plugin')
var HtmlWebpackPlugin = require('html-webpack-plugin')
// 抽取css，js文件,與webpack輸出的bundle分離
var ExtractTextPlugin = require('extract-text-webpack-plugin')
var OptimizeCSSPlugin = require('optimize-css-assets-webpack-plugin')

var env = process.env.NODE_ENV === 'testing'
  ? require('../config/test.env')
  : config.build.env
//合併webpack.base.conf
var webpackConfig = merge(baseWebpackConfig, {
  module: {
    rules: utils.styleLoaders({
      sourceMap: config.build.productionSourceMap,
      extract: true
    })
  },
  devtool: config.build.productionSourceMap ? '#source-map' : false,
  output: {
    //配置輸出路徑
    path: config.build.assetsRoot,
    //輸出的文件命名格式
    filename: utils.assetsPath('js/[name].[chunkhash].js'),
    //未指定文件名的文件的文件名格式
    chunkFilename: utils.assetsPath('js/[id].[chunkhash].js')
  },
  //相關插件
  plugins: [
    // http://vuejs.github.io/vue-loader/en/workflow/production.html
    new webpack.DefinePlugin({
      'process.env': env
    }),
    //壓縮js插件
    new webpack.optimize.UglifyJsPlugin({
      compress: {
        warnings: false
      },
      sourceMap: true
    }),
    // extract css into its own file
    //從bundle中抽取css文件
    new ExtractTextPlugin({
      filename: utils.assetsPath('css/[name].[contenthash].css')
    }),
    // Compress extracted CSS. We are using this plugin so that possible
    // duplicated CSS from different components can be deduped.
    //壓縮抽取的css文件
    new OptimizeCSSPlugin({
      cssProcessorOptions: {
        safe: true
      }
    }),
    // generate dist index.html with correct asset hash for caching.
    // you can customize output by editing /index.html
    // see https://github.com/ampedandwired/html-webpack-plugin
    //用於生成dist/index.html，加入hash用於緩存。hash不改變不進行更新
    new HtmlWebpackPlugin({
      filename: process.env.NODE_ENV === 'testing'
        ? 'index.html'
        : config.build.index,
      template: 'index.html',
      inject: true,
      minify: {
        removeComments: true,
        collapseWhitespace: true,
        removeAttributeQuotes: true
        // more options:
        // https://github.com/kangax/html-minifier#options-quick-reference
      },
      // necessary to consistently work with multiple chunks via CommonsChunkPlugin
      chunksSortMode: 'dependency'
    }),
    // split vendor js into its own file
    //分離第三方js到單獨的文件中
    new webpack.optimize.CommonsChunkPlugin({
      name: 'vendor',
      minChunks: function (module, count) {
        // any required modules inside node_modules are extracted to vendor
        return (
          module.resource &&
          /\.js$/.test(module.resource) &&
          module.resource.indexOf(
            path.join(__dirname, '../node_modules')
          ) === 0
        )
      }
    }),
    // extract webpack runtime and module manifest to its own file in order to
    // prevent vendor hash from being updated whenever app bundle is updated
    new webpack.optimize.CommonsChunkPlugin({
      name: 'manifest',
      chunks: ['vendor']
    }),
    // copy custom static assets
    new CopyWebpackPlugin([
      {
        from: path.resolve(__dirname, '../static'),
        to: config.build.assetsSubDirectory,
        ignore: ['.*']
      }
    ])
  ]
})
// 配置gzip模式
if (config.build.productionGzip) {
  var CompressionWebpackPlugin = require('compression-webpack-plugin')

  webpackConfig.plugins.push(
    new CompressionWebpackPlugin({
      asset: '[path].gz[query]',
      algorithm: 'gzip',
      test: new RegExp(
        '\\.(' +
        config.build.productionGzipExtensions.join('|') +
        ')$'
      ),
      threshold: 10240,
      minRatio: 0.8
    })
  )
}
//配置webpack-bundle-analyzer，分析打包後生成的文件結構
if (config.build.bundleAnalyzerReport) {
  var BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin
  webpackConfig.plugins.push(new BundleAnalyzerPlugin())
}

module.exports = webpackConfig

2.七、config/index.js

/*
    最後是config中的index.js文件，它都配置了什麼
*/

var path = require('path')

module.exports = {
    //打包時使用的配置
  build: {
    //webpack的環境
    env: require('./prod.env'),
    //輸入的index.html的路徑
    index: path.resolve(__dirname, '../dist/index.html'),
    //輸出的目標文件夾路徑
    assetsRoot: path.resolve(__dirname, '../dist'),
    //輸出的子文件夾路徑
    assetsSubDirectory: 'static',
    //發佈路徑
    assetsPublicPath: '/',
    //是否使用SourceMap
    productionSourceMap: true,
    // Gzip off by default as many popular static hosts such as
    // Surge or Netlify already gzip all static assets for you.
    // Before setting to `true`, make sure to:
    // npm install --save-dev compression-webpack-plugin
    // 是否開啓Gzip
    productionGzip: false,
    //Gzip的壓縮文件類型
    productionGzipExtensions: ['js', 'css'],
    // Run the build command with an extra argument to
    // View the bundle analyzer report after build finishes:
    // `npm run build --report`
    // Set to `true` or `false` to always turn it on or off
    bundleAnalyzerReport: process.env.npm_config_report
  },
  //開發時使用的配置
  dev: {
    //webpack環境
    env: require('./dev.env'),
    //端口
    port: 8080,
    //是否自動打開瀏覽器
    autoOpenBrowser: true,
    //輸出的子文件夾路徑
    assetsSubDirectory: 'static',
    //發佈路徑
    assetsPublicPath: '/',
    //配置代理表
    proxyTable: {},
    // CSS Sourcemaps off by default because relative paths are "buggy"
    // with this option, according to the CSS-Loader README
    // (https://github.com/webpack/css-loader#sourcemaps)
    // In our experience, they generally work as expected,
    // just be aware of this issue when enabling this option.
    cssSourceMap: false
  }
}

參考網址

http://www.javashuo.com/article/p-pjtiduem-gs.html