webpack.config.server.js

// @flow
const path = require('path');
const ExternalsPlugin = require('webpack-externals-plugin');

module.exports = {
  entry: ['babel-polyfill', path.resolve(__dirname, 'src/server.js')],

  output: {
    path: `${__dirname}/dist/`,
    filename: 'server.bundle.js',
  },

  target: 'node',

  node: {
    __filename: true,
    __dirname: true,
  },

  resolve: {
    extensions: ['', '.js', '.jsx'],
    modules: ['client', 'node_modules'],
  },

  module: {
    loaders: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        loader: 'babel-loader',
        query: {
          presets: ['react', 'es2015', 'stage-0'],
          plugins: [
            [
              'babel-plugin-webpack-loaders',
              {
                config: './webpack.config.babel.js',
                verbose: false,
              },
            ],
          ],
        },
      },
      {
        test: /\.json$/,
        loader: 'json-loader',
      },
    ],
  },
  plugins: [
    new ExternalsPlugin({
      type: 'commonjs',
      include: path.join(__dirname, './node_modules/'),
    }),
  ],
};