首先在package.json下有
開發(fā)環(huán)境下運(yùn)行這條命令

"dev": "node build/dev-server.js",

運(yùn)行build下的dev-server.js
這個(gè)相當(dāng)于自定義一個(gè)server 利用webpack-dev-middleware配合express來自動(dòng)生成 自己寫一個(gè)server.js
主要就是導(dǎo)入一些webpack.dev.conf或者config里面的一些生產(chǎn)環(huán)境下的配置 來自定義服務(wù)器

require('./check-versions')()

var config = require('../config') 
if (!process.env.NODE_ENV) {
  process.env.NODE_ENV = JSON.parse(config.dev.env.NODE_ENV) //如果沒有設(shè)置為生產(chǎn)模式
}

var opn = require('opn')
var path = require('path')
var express = require('express')
var webpack = require('webpack')
var proxyMiddleware = require('http-proxy-middleware')
var webpackConfig = require('./webpack.dev.conf')

// default port where dev server listens for incoming traffic
var port = process.env.PORT || config.dev.port
// automatically open browser, if not set will be false
var autoOpenBrowser = !!config.dev.autoOpenBrowser
// Define HTTP proxies to your custom API backend
// https://github.com/chimurai/http-proxy-middleware
var proxyTable = config.dev.proxyTable

var app = express()
var compiler = webpack(webpackConfig)

var devMiddleware = require('webpack-dev-middleware')(compiler, {
  publicPath: webpackConfig.output.publicPath,
  quiet: true  //向控制臺(tái)顯示任何內(nèi)容 
})

var hotMiddleware = require('webpack-hot-middleware')(compiler, {
  log: () => {}
})
// force page reload when html-webpack-plugin template changes
compiler.plugin('compilation', function (compilation) {
  compilation.plugin('html-webpack-plugin-after-emit', function (data, cb) {
    hotMiddleware.publish({ action: 'reload' })
    cb()
  })
})

// proxy api requests
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
app.use(require('connect-history-api-fallback')())

// serve webpack bundle output
app.use(devMiddleware)

// enable hot-reload and state-preserving
// compilation error display
app.use(hotMiddleware)

// serve pure static assets
var staticPath = path.posix.join(config.dev.assetsPublicPath, config.dev.assetsSubDirectory)
app.use(staticPath, express.static('./static'))

var uri = 'http://localhost:' + port

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

console.log('> Starting dev server...')
devMiddleware.waitUntilValid(() => {
  console.log('> Listening at ' + uri + '\n')
  // when env is testing, don't need open it
  if (autoOpenBrowser && process.env.NODE_ENV !== 'testing') {
    opn(uri)
  }
  _resolve()
})

var server = app.listen(port)

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

var compiler = webpack(webpackConfig) ；webpackConfig就是在生產(chǎn)環(huán)境下的webpack的配置文件 這個(gè)里面合并了公共配置文件和生產(chǎn)環(huán)境下的專有配置文件 這里就是傳入config重新編譯一次。

entry: {
    app: './src/main.js'
  },

打包文件入口為這個(gè)路徑下的文件 chunkName為app

 output: {
    path: config.build.assetsRoot,
    filename: '[name].js',
    publicPath: process.env.NODE_ENV === 'development'
      ? config.dev.assetsPublicPath
      : config.build.assetsPublicPath
  },

path:打包后的文件存放在路徑 這里找到之后是在dist下
filename： 則是生成文件的名字
publicPath：打包的時(shí)候，webpack會(huì)在靜態(tài)文件路徑前面添加publicPath的值，當(dāng)我們把資源放到CDN上的時(shí)候，把publicPath的值設(shè)為CDN的值就可以了
靜態(tài)資源最終訪問路徑 = output.publicPath + 資源loader或插件等配置路徑
在這里開發(fā)環(huán)境下靜態(tài)訪問路徑為‘/’ 即根路徑下的 生成環(huán)境下靜態(tài)訪問路徑為‘./’ 即當(dāng)前路徑下的

resolve: {
    extensions: ['.js', '.vue', '.json'],
    alias: {
      '@': resolve('src')
    },
  },