webpack.config.server.js

const webpack = require("webpack");
const path = require("path");
const nodeExternals = require("webpack-node-externals");
const StartServerPlugin = require("start-server-webpack-plugin");

module.exports = {
    mode: 'development',
    entry: [
        "webpack/hot/poll?1000",
        "./server/index"
    ],
    watch: true,
    target: "node",
    externals: [
        nodeExternals({ whitelist: [ "webpack/hot/poll?1000" ] })
    ],
    module: {
        rules: [
            { test: /\.js?$/, use: "babel-loader", exclude: /node_modules/ },
        ],
    },
    plugins: [
        new webpack.NormalModuleReplacementPlugin(/\.(css|less)$/, './empty.js'),
        new StartServerPlugin("server.js"),
        new webpack.NamedModulesPlugin(),
        new webpack.HotModuleReplacementPlugin(),
        new webpack.NoEmitOnErrorsPlugin(),
        new webpack.DefinePlugin({
            "process.env": { BUILD_TARGET: JSON.stringify("server") },
        })
    ],
    output: {
        path: path.join(__dirname, ".build"),
        filename: "server.js"
    },
};