webpack.config.js

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');

// Constant with our paths
const paths = {
    DIST: path.resolve(__dirname, 'dist-client'),
    JS: path.resolve(__dirname, 'client'),
    SRC: path.resolve(__dirname, 'client/public')
};

module.exports = {
    entry: path.join(paths.JS, 'index.js'),
    output: {
        path: paths.DIST,
        filename: 'index.bundle.js'
    },
    // Enable sourcemaps for debugging webpack's output.
    devtool: "source-map",

    resolve: {
        extensions: [".js", ".json"]
    },

    module: {
        rules: [
            {
                test: /\.(js|jsx)$/,
                exclude: /node_modules/,
                use: [
                    'babel-loader',
                ],
            },
        ],
    },

    // When importing a module whose path matches one of the following, just
    // assume a corresponding global variable exists and use that instead.
    // This is important because it allows us to avoid bundling all of our
    // dependencies, which allows browsers to cache those libraries between builds.
    externals: {
        "react": "React",
        "react-dom": "ReactDOM"
    },
    devServer: {
        historyApiFallback: true
    },
    plugins: [
        new HtmlWebpackPlugin({
            template: path.join(paths.SRC, 'index.html')
        })
    ],
};