Webpack 2 Tree Shaking

.babelrc

{
  "presets": [
    ["es2015", {
      "modules": false
    }],
    "react",
    "stage-0"
  ],
  "compact": "true",
  "plugins": [
    ["transform-relay-hot", {
      "schemaJsonFilepath": "./data/schema.json",
      "watchInterval": 2000
    }]
  ],
  "env": {
    "development": {
      "plugins": [
        "transform-react-jsx-source"
      ]
    }
  }
}

package.json

{
  ...
  "scripts": {
    "build": "webpack --config webpack.prod.config.js --progress --profile --colors"
  }
  ...
}

webpack.prod.config.js

/* eslint-disable */

const webpack = require('webpack');
const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const CleanPlugin = require('clean-webpack-plugin');
const dotEnv = require('dotenv-webpack');

module.exports = {
  // Default folder for code source
  context: path.join(__dirname, './src'),
  devtool: 'hidden-source-map',
  entry: './index.js',
  output: {
		path: path.join(__dirname, 'admin'),
    publicPath: '/admin/',
		filename: '[chunkhash].js'
	},
  resolve: {
    modules: [
      path.join(__dirname, 'src'),
      'node_modules',
    ],
    extensions: ['.js'],
  },
  module: {
    rules: [{
      test: /\.js?$/,
      exclude: [/node_modules/],
      use: [
        {
          loader: 'babel-loader',
          options: {
            babelrc: false,
            presets: [
              ['es2015', { modules: false }],
              'react',
              'stage-0',
            ],
          }
        },
      ],
      // include: path.join(__dirname, 'src'),
    }],
  },
	plugins: [
    new dotEnv({
      path: './.env',
    }),
    new webpack.LoaderOptionsPlugin({
      minimize: true,
      debug: false
    }),
    new webpack.optimize.UglifyJsPlugin({
      compress: {
        warnings: false,
        screw_ie8: true,
        drop_console: true,
        drop_debugger: true,
        dead_code: true,
        unused: true,
      },
    }),
    new CleanPlugin(['admin'], { verbose: false }),
		new HtmlWebpackPlugin({
			template: './index.html'
		}),
	]
};