webpack.common.js

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

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

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

const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
  entry: [ 'babel-polyfill', './src/app.js' ],
  output: {
    path: path.join(__dirname, 'public', 'dist'),
    filename: 'bundle.js'
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        loader: 'babel-loader'
      },
      {
        test: /\.s?css$/,
        use: [
          MiniCssExtractPlugin.loader,
          '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_ID': JSON.stringify(process.env.FIREBASE_MESSAGING_SENDER_ID)
    })
  ]
};