webpack.common.js

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

const HtmlWebPackPlugin = require('html-webpack-plugin');
const htmlPlugin = new HtmlWebPackPlugin({
  template: './src/index.html',
  filename: './index.html',
});

const CleanWebpackPlugin = require('clean-webpack-plugin');
const cleanWebpackPlugin = new CleanWebpackPlugin(['dist']);
const dotenv = require('dotenv');

module.exports.getDotEnvPlugin = (filename) => {
  const envVariables = dotenv.config({
    path: `${path.join(__dirname)}/${filename}`,
  }).parsed;
  const envKeys = Object.keys(envVariables).reduce((prev, next) => {
    prev[`process.env.${next}`] = JSON.stringify(envVariables[next]);
    return prev;
  }, {});
  return new webpack.DefinePlugin(envKeys);
}

module.exports.config = {
  entry: ['@babel/polyfill', './src/index.js'],
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader',
        },
      },
      {
        test: /\.(s*)css$/,
        use: [
          {
            loader: 'style-loader',
          },
          {
            loader: 'css-loader',
            options: {
              modules: true,
              importLoaders: 1,
              localIdentName: '[local]',
              sourceMap: true
            },
          },
          {
            loader: 'sass-loader',
          },
        ],
      },
    ],
  },
  optimization: {
    splitChunks: {
      chunks: 'all',
    },
  },
  plugins: [cleanWebpackPlugin, htmlPlugin],
  output: {
    filename: '[name].bundle.js',
    chunkFilename: '[name].bundle.js',
    path: path.resolve(__dirname, 'dist'),
  },
};