webpack.config.js

const path = require('path'),
      webpack = require('webpack'),
      nodeExternals = require('webpack-node-externals');

module.exports = (env, argv) => ({
    watch: argv.mode !== 'production',
    entry: ['babel-polyfill', './src/server.js'],
    output: {
        path: path.join(__dirname, 'dist'),
        publicPath: '/',
        filename: 'server.js'
    },
    target: 'node',
    node: {
        // Need this when working with express, otherwise the build fails
        __dirname: false,   // if you don't put this is, __dirname
        __filename: false,  // and __filename return blank or /
    },
    externals: [nodeExternals()], // Need this to avoid error when working with Express
    module: {
        rules: [
            {
                // Transpiles ES6-8 into ES5
                test: /\.js$/,
                exclude: /node_modules/,
                use: {
                    loader: "babel-loader"
                }
            }
        ]
    },
    plugins: []
});