old_contents: const path = require('path');
  const webpackMerge = require('webpack-merge');
  const ExtractTextPlugin = require('extract-text-webpack-plugin');
  const { DefinePlugin, LoaderOptionsPlugin, NoEmitOnErrorsPlugin } = require('webpack');
  const { UglifyJsPlugin } = require('webpack').optimize;
  const commonConfig = require('./webpack.common.js');
  
  const ENV = process.env.NODE_ENV = process.env.ENV = 'production';
  
  module.exports = webpackMerge(commonConfig, {
    devtool: 'inline-source-map',
  
    output: {
      path: path.resolve(__dirname, '../dist'),
      filename: '[name].[hash].js',
      chunkFilename: '[id].[hash].chunk.js'
    },
  
    plugins: [
      new NoEmitOnErrorsPlugin(),
      new ExtractTextPlugin('[name].[hash].css'),
      new DefinePlugin({
        'process.env': {
          'ENV': JSON.stringify(ENV),
          'NODE_ENV': JSON.stringify(ENV)
        }
      }),
      new UglifyJsPlugin({
        sourceMap: false,
        mangle: {
          keep_fnames: true
        },
        compress: {
          warnings: false
        },
        output: {
          comments: false
        },
      }),
      new LoaderOptionsPlugin({
        htmlLoader: {
          minimize: false
        }
      })
    ],
    devServer: {
      historyApiFallback: true
    }
  });
  
new_contents: const path = require('path');
  const webpackMerge = require('webpack-merge');
  const ExtractTextPlugin = require('extract-text-webpack-plugin');
  const { DefinePlugin, LoaderOptionsPlugin, NoEmitOnErrorsPlugin } = require('webpack');
  const { UglifyJsPlugin } = require('webpack').optimize;
  const commonConfig = require('./webpack.common.js');
  
  const ENV = process.env.NODE_ENV = process.env.ENV = 'production';
  
  module.exports = webpackMerge(commonConfig, {
    devtool: '',
  
    output: {
      path: path.resolve(__dirname, '../dist'),
      filename: '[name].[hash].js',
      chunkFilename: '[id].[hash].chunk.js'
    },
  
    plugins: [
      new NoEmitOnErrorsPlugin(),
      new ExtractTextPlugin('[name].[hash].css'),
      new DefinePlugin({
        'process.env': {
          'ENV': JSON.stringify(ENV),
          'NODE_ENV': JSON.stringify(ENV)
        }
      }),
      new UglifyJsPlugin({
        sourceMap: false,
        mangle: {
          keep_fnames: true
        },
        compress: {
          warnings: false
        },
        output: {
          comments: false
        },
      }),
      new LoaderOptionsPlugin({
        htmlLoader: {
          minimize: false
        }
      })
    ],
    devServer: {
      historyApiFallback: true
    }
  });
  
subject: update prod