webpack.config.js

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

module.exports = {
  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader"
        }
      },
      {
        test: /\.html$/,
        use: [
          {
            loader: "html-loader"
          }
        ]
      },
      {
        test: /\.s[ac]ss$/i,
        use: [
          MiniCssExtractPlugin.loader,
          {
            loader: 'css-loader'
          },
          {
            loader: 'sass-loader',
            options: {
              sourceMap: true,
              // options...
            }
          }
        ]
      }
    ]
  },
  plugins: [
    new HtmlWebPackPlugin({
      template: "./src/index.html",
      filename: "./index.html"
    }),
    new MiniCssExtractPlugin({
      filename: 'css/style.css'
    }),
    new webpack.ProvidePlugin({
      'React':     'react',
      'ReactDOM':  'react-dom',
    })
  ]
};