webpack.config.js

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

module.exports = {
  entry: ["@babel/polyfill", "./src/index.js"],
  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        exclude: /node_modules/,
        use: ["babel-loader"]
      },
      { 
        test: /\.(sa|sc|c)ss$/,
        use: [
          "style-loader",
          "css-loader",
          "sass-loader"
        ]
      }
    ]
  },
  output: {
    path: __dirname + "/build",
    publicPath: "/",
    filename: "bundle.js"
  },
  plugins: [
    new MiniCssExtractPlugin(),
    new webpack.HotModuleReplacementPlugin(),
    new HtmlWebpackPlugin({
      inject: true,
      template: path.resolve(__dirname, "./public/index.html")
    })
  ],
  devServer: {
    contentBase: "./public",
    hot: true,
    historyApiFallback: true,
    publicPath: '/'
  }
};