Koa2取代webpack-dev-server作为开发环境服务器

安装相关依赖

yarn add koa koa-static koa-convert koa-webpack-middleware -D

• koa-convert: 由于koa2中使用async await异步中间件，而koa-webpack-middleware仍然是generator函数，需要用koa-convert转换下

sever.js

const Koa = require('koa')
const webpack = require('webpack')
const serve = require('koa-static')
const convert  = require('koa-convert')
const koaWebpackMiddleware = require('koa-webpack-middleware')
const webpackDevMiddleware = koaWebpackMiddleware.devMiddleware
const webpackHotMiddleware = koaWebpackMiddleware.hotMiddleware

const app = new Koa()
const config = require('./webpack.config')
const compiler = webpack(config)

const wdm = webpackDevMiddleware(compiler, {
  watchOptions: {
    aggregateTimeout: 300,
    poll: true
  },
  reload: true,
  publicPath: config.output.publicPath,
  stats: {
    colors: true
  }
})
app.use(convert(wdm))

app.use(convert(webpackHotMiddleware(compiler)))

app.use(serve(config.output.publicPath))

const server = app.listen(3000, 'localhost', function (err) {
  if (err) {
    console.error(err)
    return
  }
  console.log('Example app listening on port 3000!\n');
});