webpack.config.js

var path = require('path');

module.exports = {
    mode: 'production',
    entry: './src/index.js',
    output: {
        path: path.resolve(__dirname, 'public'),
        filename: 'bundle.js'
    },
    module: {
        rules: [
            {
                test: /\.m?js$/,
                exclude: /node_modules/,
                use: {
                    loader: 'babel-loader',
                    options: {
                        presets: [
                            '@babel/preset-env',
                            '@babel/preset-react'
                        ],
                        plugins: ['@babel/plugin-proposal-class-properties']
                    }
                }
            },
            {
                test: /\.s?css$/,
                use: [
                    // Creates `style` nodes from JS strings
                    "style-loader",
                    // Translates CSS into CommonJS
                    "css-loader",
                    // Compiles Sass to CSS
                    "sass-loader",
                ]  
            }
        ]
    },
    devtool: 'eval-cheap-module-source-map',
    devServer: {
        contentBase: path.join(__dirname, 'public'),
        compress: true,
        port: 9000
    }
};