webpack.prod.js

const webpack = require('webpack');
const path = require('path');

module.exports = {
  entry: path.join(__dirname, 'src', 'index.js'),
  output: {
    path: path.join(__dirname, 'dist', 'js'),
    filename: 'app.js',
    sourceMapFilename: 'app.map'
  },
  module: {
    loaders: [{
      test: path.join(__dirname, 'src'),
      loader: ['babel-loader'],
      query: {
        cacheDirectory: 'babel_cache',
        presets: ['react', 'es2015']
      }
    }, {
      include: /\.json$/,
      loaders: ["json-loader"]
    }]
  },
  resolve: {
    extensions: ['', '.json', '.jsx', '.js']
  },
  plugins: [
    new webpack.DefinePlugin({
      'process.env.NODE_ENV': JSON.stringify(process.env.NODE_ENV)
    }),
    new webpack.optimize.DedupePlugin(),
    new webpack.optimize.OccurenceOrderPlugin(),
    new webpack.optimize.UglifyJsPlugin({
			beautify: false,
      output: {
        comments: false
      },
      mangle: {
        screw_ie8: true
      },
      compress: {
        screw_ie8: true,
        warnings: false,
        conditionals: true,
        unused: true,
        comparisons: true,
        sequences: true,
        dead_code: true,
        evaluate: true,
        if_return: true,
        join_vars: true
      }
    })
  ]
};