深入探索 vue-cli，讓我們來看看 build/build.js 與 build/webpack.dev.conf.js 做了些什麼！

2018鐵人賽

Alex Tzeng, 曾苔眠

2017-12-30 16:44:28

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Hi 大家好

昨天我們回到了最一開始讀不懂的 package.json

試著使用我們這幾週學到的知識，是否可以應用在讀懂 vue-cli 的 boilerplate

這邊有兩個檔案，build/webpack.dev.conf.js 和 build/build.js

build/webpack.dev.config.js，他是我們 npm run dev 時所使用的設定檔

而 build/build.js，我們則會把它應用在 npm run build

就是我們要打包出實際上 production 環境的 code

(因為編譯要很久，我們一般開發都是使用 npm run dev)

這邊，就讓我們一起來讀懂 source code 吧！

`webpack.dev.conf.js`

'use strict'
const utils = require('./utils')
const webpack = require('webpack')
const config = require('../config')
const merge = require('webpack-merge')
const baseWebpackConfig = require('./webpack.base.conf')
const HtmlWebpackPlugin = require('html-webpack-plugin')
const FriendlyErrorsPlugin = require('friendly-errors-webpack-plugin')
const portfinder = require('portfinder')

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: config.dev.devtool,

  // these devServer options should be customized in /config/index.js
  devServer: {
    clientLogLevel: 'warning',
    historyApiFallback: true,
    hot: true,
    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: [
    new webpack.DefinePlugin({
      'process.env': require('../config/dev.env')
    }),
    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
    }),
  ]
})

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)
    }
  })
})

他的原始碼不太長，我們來慢慢看

我們這邊來先把 webpack.dev.conf.js 前面設定的 const(常數) 來一個一個看