webpack.config.js

const path = require('path');

module.exports = {
  mode: process.env.NODE_ENV,
  entry: './client/index.js',
  output: {
    filename: 'bundle.js',
    path: `${__dirname}/dist`,
  },
  devServer: {
    publicPath: '/dist/',
    proxy: {
      '/': 'http://localhost:4000/',
      '/socket.io': { // connection to socket.io
        target: 'http://localhost:4000',
        ws: true
    }
    },
  },
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          {
            loader: 'style-loader', // inject CSS to page
          },
          {
            loader: 'css-loader', // translates CSS into CommonJS modules
          },
          {
            loader: 'postcss-loader', // Run postcss actions
            options: {
              plugins() {
                // postcss plugins, can be exported to postcss.config.js
                return [require('precss'), require('autoprefixer')];
              },
            },
          },
          {
            loader: 'sass-loader', // compiles Sass to CSS
          },
        ],
      },
      {
        test: /\.s[ac]ss$/i,
        exclude: /node_modules/,
        use: ['style-loader', 'css-loader', 'sass-loader'],
      },
      {
        test: /\.jsx?/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['@babel/preset-env', '@babel/preset-react'],
          },
        },
      },
    ],
  },
  resolve: {
    // Enable importing JS / JSX files without specifying their extension
    modules: [path.resolve(__dirname, 'node_modules')],
    extensions: ['.js', '.jsx', '.json', '.scss', '.less', '.css'],
  },
};