webpack.config.js

const path = require("path");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");

module.exports = env => {
  const isProduction = env === "production" ? "production" : "development";
  console.log(env);
  console.log(isProduction);

  return {
    mode: isProduction,
    entry: "./src/app.js",
    output: {
      path: path.join(__dirname, "public"),
      filename: "bundle.js"
    },
    module: {
      rules: [
        {
          loader: "babel-loader",
          test: /\.js$/,
          exclude: /node_modules/
        },
        {
          test: /\.s?css$/,
          use: [MiniCssExtractPlugin.loader, "css-loader", "sass-loader"]
        }
      ]
    },
    plugins: [
      new MiniCssExtractPlugin({
        filename: "styles.css"
      })
    ],
    devtool: "cheap-module-eval-source-map",
    devServer: {
      contentBase: path.join(__dirname, "public")
    }
  };
};