title: Webpack "start": "webpack-dev-server --config=config/webpack.dev.js", not working
body: <p>I am learning react and Webpack dev server is not starting and giving me this error </p>
  
  <p>internal/modules/cjs/loader.js:573
      throw err;
      ^
  Error: Cannot find module 'webpack'</p>
  
  <p>Scripts </p>
  
  <pre><code>"scripts": {
  "start": "webpack-dev-server --config=config/webpack.dev.js",
  "build": "NODE_ENV=production webpack --config=config/webpack.prod.js",
  "compile": "webpack --config webpack.config.js"
  </code></pre>
  
  <p>},</p>
  
  <p>Terminal output </p>
  
  <pre><code> npm start
  </code></pre>
  
  <blockquote>
    <p>react-shopping-cart@0.1.0 start C:\Users\iClick Digital\                                                                             Documents\ZerotoMastery\frontendprojects\react-shopping-ca                                                                             rt
    webpack-dev-server --config=config/webpack.dev.js</p>
  </blockquote>
  
  <p>internal/modules/cjs/loader.js:573
      throw err;
      ^</p>
  
  <p>Error: Cannot find module 'webpack'
      at Function.Module._resolveFilename (internal/modules/                                                                             cjs/loader.js:571:15)
      at Function.Module._load (internal/modules/cjs/loader.                                                                             js:497:25)
      at Module.require (internal/modules/cjs/loader.js:626:                                                                             17)
      at require (internal/modules/cjs/helpers.js:20:18)
      at Object. (C:\Users\iClick Digital\Documen                                                                             ts\ZerotoMastery\frontendprojects\react-shopping-cart\conf                                                                             ig\webpack.dev.js:2:17)
      at Module._compile (internal/modules/cjs/loader.js:678                                                                             :30)
      at Object.Module._extensions..js (internal/modules/cjs                                                                             /loader.js:689:10)
      at Module.load (internal/modules/cjs/loader.js:589:32)
      at tryModuleLoad (internal/modules/cjs/loader.js:528:1                                                                             2)
      at Function.Module._load (internal/modules/cjs/loader.                                                                             js:520:3)
  npm ERR! code ELIFECYCLE
  npm ERR! errno 1
  npm ERR! react-shopping-cart@0.1.0 start: <code>webpack-dev-ser                                                                             ver --config=config/webpack.dev.js</code>
  npm ERR! Exit status 1
  npm ERR!
  npm ERR! Failed at the react-shopping-cart@0.1.0 start scr                                                                             ipt.
  npm ERR! This is probably not a problem with npm. There is                                                                              likely additional logging output above.
  npm WARN Local package.json exists, but node_modules missi                                                                             ng, did you mean to install?</p>
  
  <p>npm ERR! A complete log of this run can be found in:
  npm ERR!     C:\Users\iClick Digital\AppData\Roaming\npm-c                                                                             ache_logs\2018-09-02T12_06_07_432Z-debug.log</p>