webpack.server.config.js

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

module.exports = (env, argv) => {
    const SERVER_PATH = (argv.mode === 'production') ? './src/server/server-prod.js' : './src/server/server-dev.js'

    return ({
        entry: {
            server: SERVER_PATH,
        },
        output: {
            path: path.join(__dirname, 'dist'),
            publicPath: '/',
            filename: '[name].js',
        },
        target: 'node',
        node: {
            // Need this when working with Express,
            // otherwise the build failed
            __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'
                    }
                }
            ]
        }
    })
}