Webpack 4 babel-loader config

config.js

/*
  Relevant packages used:
  -----------------------
  
  "@babel/core": "^7.0.0-beta.40",
  "@babel/plugin-proposal-class-properties": "^7.0.0-beta.40",
  "@babel/plugin-proposal-object-rest-spread": "^7.0.0-beta.40",
  "@babel/preset-env": "^7.0.0-beta.40",
  "@babel/preset-react": "^7.0.0-beta.40",
  "babel-loader": "^8.0.0-beta.2",
  "webpack": "^4.2.0",
  "webpack-cli": "^2.0.10",
*/

{
  test: /\.(js|jsx)$/,
  exclude: /node_modules/, // This may not be needed since we supplied `include`.
  include: path.resolve(__dirname, 'src'),

  /*
    https://goo.gl/99S6sU
    Loaders will be applied from right to left.
    E.x.: loader3(loader2(loader1(data)))
  */
  use: [
    // https://goo.gl/EXjzoG
    {
      loader: 'babel-loader',
      options: {
        presets: [
          /*
            To get tree shaking working, we need the `modules: false` below.

            https://goo.gl/4vZBSr - 2ality blog mentions that the issue is caused
            by under-the-hood usage of `transform-es2015-modules-commonjs`.

            https://goo.gl/sBmiwZ - A comment on the above post shows that we
            can use `modules: false`.

            https://goo.gl/aAxYAq - `babel-preset-env` documentation.
          */
          [
            '@babel/preset-env',
            {
              targets: {
                browsers: [
                  'last 2 versions'
                ]
              },
              modules: false // Needed for tree shaking to work.
            }
          ],
          // '@babel/preset-env', // https://goo.gl/aAxYAq
          '@babel/preset-react' // https://goo.gl/4aEFV3
        ],

        // https://goo.gl/N9gaqc - List of Babel plugins.
        plugins: [
          '@babel/plugin-proposal-object-rest-spread', // https://goo.gl/LCHWnP
          '@babel/plugin-proposal-class-properties' // https://goo.gl/TE6TyG
        ]
      }
    }
  ]
}