A somewhat minimal webpack config file for JS via Babel, with a dev server and hot module replacement.

webpack.config.js

'use strict';

const path = require('path');
const webpack = require('webpack');

module.exports = {
    /** @see https://webpack.js.org/configuration/entry-context/#entry */
    entry: './src/js/index.js',

    /** @see https://webpack.js.org/configuration/output/ */
    output: {
        filename: 'bundle.js',
        path: path.resolve(__dirname, 'dist')
    },

    /** @see https://webpack.js.org/configuration/dev-server/ */
    devServer: {
        contentBase: path.join(__dirname, 'dist'),
        compress: true,
        hot: true,
        open: true,
        overlay: true,
        port: 8080
    },

    /** @see https://webpack.js.org/configuration/devtool/ */
    devtool: 'source-map',

    /** @see https://webpack.js.org/configuration/resolve/ */
    resolve: {
        extensions: ['.js']
    },

    /** @see https://webpack.js.org/configuration/module/ */
    module: {
        rules: [
            {
                test: /\.js$/,
                loader: 'babel-loader',
                options: {
                    presets: ['env']
                },
                exclude: /node_modules/
            }
        ]
    },

    /** @see https://webpack.js.org/configuration/plugins/ */
    plugins: [
       new webpack.HotModuleReplacementPlugin()
    ]
}

Install dependencies via: yarn add --dev babel-core babel-loader babel-preset-env webpack webpack-dev-server.