webpack.config.js

const webpack = require('webpack');
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const devMode = true;

module.exports = {
    entry: [
        'react-hot-loader/patch',
        './src/app.js'
    ],
    devtool: "cheap-eval-source-map",
    module: {
        rules: [
            {
                test: /\.(js|jsx)$/,
                exclude: /node_modules/,
                use: ['babel-loader']
            },
            {
                test: /\.(sa|sc|c)ss$/,
                use: [
                    devMode ? 'style-loader' : MiniCssExtractPlugin.loader,
                    'css-loader',
                    'sass-loader',
                ],
            }
        ]
    },
    resolve: {
        extensions: ['*', '.js', '.jsx']
    },
    output: {
        path: __dirname + '/dist',
        publicPath: '/',
        filename: 'bundle.js'
    },
    plugins: [
        new MiniCssExtractPlugin({
            // Options similar to the same options in webpackOptions.output
            // both options are optional
            filename: devMode ? '[name].css' : '[name].[hash].css',
            chunkFilename: devMode ? '[id].css' : '[id].[hash].css',
        }),
        new webpack.HotModuleReplacementPlugin()
    ],
    devServer: {
        contentBase: './dist',
        hot: true,
        historyApiFallback: true,
        headers: {
            'Access-Control-Allow-Origin': '*'
        }
    }
};