Basic Webpack 5 + HMR basic setup (multiple files)

webpack.common.js

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const CopyPlugin = require('copy-webpack-plugin');
const { CleanWebpackPlugin } = require('clean-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

const isProd = process.env.NODE_ENV === 'production';
const isDev = !isProd;

const filename = ext => isProd ? `bundle.[fullhash].${ext}` : `bundle.${ext}`;

module.exports = {
    target: 'web',
    context: path.resolve(__dirname, '../src'),
    entry: './index.js',
    output: {
        path: path.resolve(__dirname, '../dist'),
        filename: filename('js'),
    },
    resolve: {
        extensions: ['.js'],
        alias: {
            '@': path.resolve(__dirname, '../src'),
            '@core': path.resolve(__dirname, '../src/core')
        }
    },
    module: {
        rules: [
            {
                test: /\.m?js$/,
                exclude: /node_modules/,
                use: {
                    loader: "babel-loader",
                    options: {
                        presets: ['@babel/preset-env']
                    }
                }
            },
            {
                test: /\.s[ac]ss$/i,
                use: [
                    MiniCssExtractPlugin.loader,
                    // Translates CSS into CommonJS
                    'css-loader',
                    // Compiles Sass to CSS
                    'sass-loader',
                ],
            },
        ]
    },
    plugins: [
        new CleanWebpackPlugin(),
        new HtmlWebpackPlugin({
            template: 'index.html',
            minify: {
                removeComments: isProd,
                collapseWhitespace: isProd
            }
        }),
        new CopyPlugin({
            patterns: [
                {
                    from: path.resolve(__dirname, '../src/favicon.ico'),
                    to: path.resolve(__dirname, '../dist'),
                }
            ]
        }),
        new MiniCssExtractPlugin({
            filename: filename('css'),
        })
    ]
}

webpack.dev.js

const path = require('path');
const webpack = require('webpack');
const { merge } = require('webpack-merge');
const common = require('./webpack.common');

const isProd = process.env.NODE_ENV === 'production';
const isDev = !isProd;

module.exports = merge(common, {
    mode: 'development',
    devtool: isDev ? 'source-map' : false,
    devServer: {
        open: true,
        compress: true,
        hot: true,
        port: 8080,
    },
    plugins: [
        new webpack.HotModuleReplacementPlugin(),
    ]
})