一开始装webpack建议先装低一点版本，所以npm i -D webpack@3 装了个3.12版本的,然后装了webpack-dev-server

配置如下：

{
  "name": "WebPack",
  "version": "1.0.0",
  "description": "",
  "main": "webpack.config.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "dev": "webpack",
    "start": "webpack-dev-server"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "babel-core": "^6.26.3",
    "babel-loader": "^7.1.4",
    "babel-preset-react": "^6.24.1",
    "html-webpack-plugin": "^3.2.0",
    "webpack": "^3.12.0",
    "webpack-dev-server": "^3.1.4"
  },
  "dependencies": {
    "react": "^16.4.1",
    "react-dom": "^16.4.1"
  }
}

然后运行npm run start提示要安装webpack-cli,然后就装呗 npm i -D webpack-cli,装出来是

"webpack-cli": "^3.0.8",运行npm run start又报了个错

> webpack-dev-server

xx/web/node_modules/_webpack-dev-server@3.12@webpack-dev-server/bin/webpack-dev-server.js:405
    throw e;
    ^

TypeError: Cannot read property 'compile' of undefined

TypeError: Cannot read property 'compile' of undefined

这个错误，同理如果webpack是3.x,则webpack-dev-server必须是2.x 

于是将webpack卸载npm uninstall webpack然后再npm install webpack这时候装上去的默认是最新的版本，我此次装的是4.14版本，然后再次npm run start就可以正常运行了