webpack.config.js

const path = require('path');
const webpack = require('webpack');

process.env.NODE_ENV = process.env.NODE_ENV || 'development';

if (process.env.NODE_ENV === 'test') {
  require('dotenv').config({ path: '.env.test' });
} else if (process.env.NODE_ENV === 'development') {
  require('dotenv').config({ path: '.env.development' });
}

module.exports = (env) => {
  const isProduction = env === 'production';
  const MiniCssExtractPlugin = require('mini-css-extract-plugin');

  return {
    entry: ['babel-polyfill', './src/app.js'],
    output: {
      path: path.join(__dirname, 'public', 'dist'),
      filename: 'bundle.js',
    },
    mode: 'development',
    devtool: isProduction ? 'source-map' : 'cheap-module-eval-source-map',
    devServer: {
      contentBase: path.join(__dirname, 'public'),
      historyApiFallback: true,
      publicPath: '/dist/',
    },
    module: {
      rules: [
        {
          test: /\.jsx?$/,
          loader: 'babel-loader',
          exclude: /node_modules/,
          resolve: {
            extensions: ['.js', '.jsx'],
          },
        },
        {
          test: /\.s?css$/,
          use: [
            {
              loader: MiniCssExtractPlugin.loader,
              options: {
                publicPath: (resourcePath, context) => `${path.relative(path.dirname(resourcePath), context)}/`,
              },
            },
            'css-loader',
            'sass-loader',
          ],
        },
      ],
    },
    plugins: [
      new MiniCssExtractPlugin({
        filename: 'styles.css',
      }),
      new webpack.DefinePlugin({
        'process.env.FIREBASE_API_KEY': JSON.stringify(process.env.FIREBASE_API_KEY),
        'process.env.FIREBASE_AUTH_DOMAIN': JSON.stringify(process.env.FIREBASE_AUTH_DOMAIN),
        'process.env.FIREBASE_DATABASE_URL': JSON.stringify(process.env.FIREBASE_DATABASE_URL),
        'process.env.FIREBASE_PROJECT_ID': JSON.stringify(process.env.FIREBASE_PROJECT_ID),
        'process.env.FIREBASE_STORAGE_BUCKET': JSON.stringify(process.env.FIREBASE_STORAGE_BUCKET),
        'process.env.FIREBASE_MESSAGING_SENDER': JSON.stringify(process.env.FIREBASE_MESSAGING_SENDER),
        'process.env.FIREBASE_APP_ID': JSON.stringify(process.env.FIREBASE_APP_ID),
      }),
    ],
  };
};