webpack-dev.config.js

const path = require("path");
const webpack=require("webpack");

const use= [
    {   loader: "babel-loader",
    }
]

const env=process.env.NODE_ENV || 'development';
if(env!=='development') console.error("NODE_ENV is",env, "but needs to be 'development' when the server runs");

module.exports = {
    context: path.resolve(__dirname, "app"),
    mode: 'development',
    watch: true,
    devtool: 'source-map',
    entry: {
    'only-dev-server':    'webpack/hot/only-dev-server', // "only" prevents reload on syntax errors
     main:   "./client/main.js",
    },
    output: {
        path: path.join(__dirname, "assets/webpack"),
        filename: "[name].js"
    },
    module: {
        rules: [
            {
                test: /\.jsx$/,
                exclude: /node_modules/,
                include: /(.*profile.*)/, // for some reason, webpack (4.25.1) will exclude files with names containing 'profile' (or 'profile-' not sure) so I has to explicitly include them
                use,
            },
            {
                test: /\.js$/,
                exclude: /node_modules/,
                use,
            },
            {
                test: /\.jsx$/,
                exclude: /node_modules/,
                use,
            }
        ]
    },
    resolve: {
        extensions: ['*','.js','.jsx'],
    },
    node: {
        fs: 'empty' // logger wants to require fs though it's not needed on the browser
    },
    devServer: {
        disableHostCheck: true,
        publicPath: '/assets/webpack/',  // in main.js also ass if(typeof ___webpack_public_path__ !== 'undefined' __webpack_public_path__ = "http://localhost:3011/assets/webpack/";  // this is where the hot loader sends requests to
        hot: true,
        hotOnly: true,
        host: '0.0.0.0',
        port: 3011,
        index: '', // specify to enable root proxying
        proxy: { // the dev server will proxy all traffic other than publicPath to target below.
            context: () => true,
            '/': 'http://localhost:3012'  // this is where the node server of the application is really running
        }
    },
    plugins:[
        new webpack.IgnorePlugin(/nodemailer/), // not used in the client side - those should be move outside of the app directory
        new webpack.NormalModuleReplacementPlugin(/.+models\/.+/,'../models/client-side-model'), // do not include models on the client side - the app/api files contain server side and client side code
        new webpack.HotModuleReplacementPlugin()  // DO NOT use --hot in the command line - it will cause a stack overflow on the client
    ]
};