title: Webpack output is empty object
body: <p>I want to build a react component library as a node module to then import it into different projects. But if I try to import a component it just returns an empty object.</p>
  
  <p>button.jsx:</p>
  
  <pre><code>import React, {Component} from 'react'
  
  export class Button extends Component {
  
     render() {
         return &lt;button className='btn'&gt;Hello Button comp&lt;/button&gt;
     }
  }
  
  export default Button
  </code></pre>
  
  <p>index.js</p>
  
  <pre><code>var Button = require('./button/button').default;
  
  module.exports  = {
     Button: Button
  }
  </code></pre>
  
  <p>webpack.config.js</p>
  
  <pre><code>const Path = require('path');
  
  module.exports = {
     resolve: {
        extensions: ['.js', '.jsx']
     },
     entry: {
        app: './src/components/index.js'
     },
     output: {
        path: __dirname,
        filename: 'bundle.js'
     },
     module: {
      rules: [
          {
              test: /\.jsx$/,
              loader: 'babel-loader',
              query: {
                  presets: [
                      'es2015',
                      'react'
                  ]
              },
              exclude: /node_modules/,
              include: [
                  Path.resolve(__dirname, 'src')
              ]
          },
          {
              test: /\.js$/,
              loader: 'babel-loader',
              query: {
                  presets: [
                      'es2015',
                      'react'
                  ]
              },
              exclude: /node_modules/,
              include: [
                  Path.resolve(__dirname, 'src')
              ]
          }
      ]
    }
  }
  </code></pre>
  
  <p>Main property in package.json is bundle.js</p>
  
  <p>I figured out that when I import Button in a project it is just an empty object. It seems to me as if webpack doesn't bundle the index file properly. Any ideas what could be wrong here?</p>