webpack.common.js

const path = require('path');
const webpack = require('webpack');
const ExtractTextPlugin = require('extract-text-webpack-plugin');

module.exports = (env) => {
  return {
    entry: ['babel-polyfill', './src/app.jsx'],
    output: {
      path: path.join(__dirname, 'public', 'dist'),
      filename: 'bundle.js',
    },
    module: {
      rules: [
        {
          test: /\.(js|jsx)$/,
          exclude: /node_modules/,
          use: ['babel-loader', 'eslint-loader']
        },
        {
          test: /\.s?css$/,
          use: ExtractTextPlugin.extract({
            use: [
              {
                loader: 'css-loader',
                options: {
                  sourceMap: true,
                },
              },
              {
                loader: 'sass-loader',
                options: {
                  sourceMap: true,
                },
              },
            ],
          }),
        },
      ],
    },
    resolve: {
      extensions: ['.js', '.json', '.jsx'],
    },
    plugins: [
      new ExtractTextPlugin('styles.css'),
      new webpack.DefinePlugin({
        'process.env.FIREBASE_API_KEY': JSON.stringify(env.FIREBASE_API_KEY),
        'process.env.FIREBASE_AUTH_DOMAIN': JSON.stringify(env.FIREBASE_AUTH_DOMAIN),
        'process.env.FIREBASE_DATABASE_URL': JSON.stringify(env.FIREBASE_DATABASE_URL),
        'process.env.FIREBASE_PROJECT_ID': JSON.stringify(env.FIREBASE_PROJECT_ID),
        'process.env.FIREBASE_STORAGE_BUCKET': JSON.stringify(env.FIREBASE_STORAGE_BUCKET),
        'process.env.FIREBASE_MESSAGING_SENDER_ID': JSON.stringify(env.FIREBASE_MESSAGING_SENDER_ID),
      }),
    ],
  };
};