webpack.config.js

const path = require('path');
const productionConfig = merge([

    parts.generateSourceMaps({ type: 'source-map' }),
  ]);

module.exports = {
    entry: './src/app.js',
    output: {
        path: path.join(__dirname, 'public'),
        filename: 'bundle.js',
    },
    module: {
        loaders: [
            {
                test: /\.(js|jsx)$/,
                exclude: [/node_modules/, /public/],
                loader: 'babel-loader',
                query: {
                    presets: ['env'],
                }
            },
        ],
    },
};