Extension/webpack.config.babel.js

import webpack from 'webpack';
import HtmlWebpackPlugin from 'html-webpack-plugin';
import ChromeExtensionReloader from 'webpack-chrome-extension-reloader';
import CopyPlugin from 'copy-webpack-plugin';
import path from 'path';

const { NODE_ENV = 'development' } = process.env;

const base = {
  context: __dirname,
  entry: {
    background: './src/background/index.js',
    'content-script': './src/content-scripts/index.js',
    popup: './src/popup/popup.js'
  },
  output: {
    path: path.join(__dirname, 'build'),
    filename: '[name].js'
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        loader: 'babel-loader'
      },
      {
        test: /\.scss$/,
        use: [
          {
            loader: 'style-loader' // creates style nodes from JS strings
          },
          {
            loader: 'css-loader' // translates CSS into CommonJS
          },
          {
            loader: 'sass-loader' // compiles Sass to CSS
          }
        ]
      }
    ]
  },
  plugins: [
    new CopyPlugin([
      { from: './src/manifest.json', to: './manifest.json' },
      { from: './src/assets/images', to: './images' }
    ]),
    new HtmlWebpackPlugin({
      template: './src/popup/popup.html',
      chunks: ['popup']
    }),
    new webpack.DefinePlugin({
      'process.env': {
        NODE_ENV: JSON.stringify(NODE_ENV)
      }
    })
  ]
};

const development = {
  ...base,
  mode: 'development',
  devtool: '#eval-module-source-map',
  module: {
    ...base.module
  },
  plugins: [
    ...base.plugins,
    new webpack.HotModuleReplacementPlugin(),
    new ChromeExtensionReloader()
  ]
};

const production = {
  ...base,
  output: {
    path: path.join(__dirname, 'dist'),
    filename: '[name].js'
  },
  mode: 'production',
  devtool: '#source-map',

  plugins: [
    ...base.plugins,
    new webpack.LoaderOptionsPlugin({
      minimize: true,
      debug: false
    })
  ]
};

if (NODE_ENV === 'development') {
  module.exports = development;
} else {
  module.exports = production;
}