webpack.dev.js

const path = require('path');

module.exports = {
    mode: 'development',
    // eslint-disable-next-line no-undef
    entry: path.join(__dirname, 'src', 'dev', 'index.js'),
    output: {
        // eslint-disable-next-line no-undef
        path: path.join(__dirname, 'build'),
        filename: 'bundle.js',
    },
    devServer: {
        // eslint-disable-next-line no-undef
        contentBase: path.join(__dirname, 'public'),
        port: 9000,
    },
    module: {
        rules: [
            {
                test: /\.m?js|\.m?jsx$/,
                exclude: /(node_modules|bower_components)/,
                use: [
                    {
                        loader: 'babel-loader',
                        options: {
                            presets: ['@babel/react', '@babel/preset-env'],
                        },
                    },
                    'eslint-loader',
                ],
            },
            {
                test: /\.css$/i,
                use: ['style-loader', 'css-loader'],
            },
        ],
    },
};