sass/sass module, react,

webpack.config.js

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


let isDevelopment = process.env.NODE_ENV;

module.exports = {
  entry: './src/index.js',
  output: {
    filename: 'bundle.js',
    path: path.resolve(__dirname, 'dist')
  },
  devServer: {
    contentBase: path.join(__dirname, 'src'),
    watchContentBase: true,
    hot: true,
  },
  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader",
        }
      },
      {
        test: /\.module\.s(a|c)ss$/,
        loader: [
          isDevelopment ? 'style-loader' : MiniCssExtractPlugin.loader,
          {
            loader: 'css-loader',
            options: {
              modules: true,
              localIdentName: '[name]__[local]___[hash:base64:5]',
              camelCase: true,
              sourceMap: isDevelopment
            }
          },
          {
            loader: 'sass-loader',
            options: {
              sourceMap: isDevelopment
            }
          }
        ]
      },
      {
        test: /\.s(a|c)ss$/,
        exclude: /\.module.(s(a|c)ss)$/,
        loader: [
          isDevelopment ? 'style-loader' : MiniCssExtractPlugin.loader,
          'css-loader',
          {
            loader: 'sass-loader',
            options: {
              sourceMap: isDevelopment
            }
          }
        ]
      }
    ]
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: isDevelopment ? '[name].css' : '[name].[hash].css',
      chunkFilename: isDevelopment ? '[id].css' : '[id].[hash].css'
    }),
    new webpack.HotModuleReplacementPlugin()
  ]
};

"devDependencies": {
"@babel/core": "^7.4.5",
"@babel/preset-env": "^7.4.5",
"@babel/preset-react": "^7.0.0",
"babel-loader": "^8.0.6",
"css-loader": "^2.1.1",
"mini-css-extract-plugin": "^0.5.0",
"node-sass": "^4.12.0",
"sass-loader": "^7.1.0",
"style-loader": "^0.23.1",
"webpack": "^4.28.4",
"webpack-cli": "^3.2.1",
"webpack-dev-server": "^3.1.14",
}

// .babelrc
{
"presets": ["@babel/preset-env", "@babel/preset-react"]
}