old_contents: const webpack = require('webpack');
  
  const envToBeInjected = {
    OPEN_WEATHER_API_KEY: process.env.OPEN_WEATHER_API_KEY,
    NODE_ENV: process.env.NODE_ENV || 'development'
  };
  
  module.exports = {
    entry: [
      './src/index.js'
    ],
    output: {
      path: __dirname,
      publicPath: '/',
      filename: 'bundle.js'
    },
    module: {
      loaders: [
        {
          test: /\.jsx?$/,
          loader: 'babel-loader',
          exclude: /node_modules/,
          query: {
            cacheDirectory: true,
            presets: ['react', 'es2015', 'stage-1']
          }
        }
      ]
    },
    resolve: {
      extensions: ['', '.js', '.jsx']
    },
    devServer: {
      historyApiFallback: true,
      contentBase: './'
    },
    plugins: [
      new webpack.LoaderOptionsPlugin({
        minimize: true,
        debug: false
      }),
      new webpack.DefinePlugin({
        'process.env': JSON.stringify(envToBeInjected)
      }),
      new webpack.optimize.UglifyJsPlugin({
        beautify: false,
        mangle: {
          screw_ie8: true,
          keep_fnames: true
        },
        compress: {
          screw_ie8: true
        },
        comments: false
      })
    ]
  };
  
new_contents: const webpack = require('webpack');
  
  const envToBeInjected = {
    OPEN_WEATHER_API_KEY: process.env.OPEN_WEATHER_API_KEY,
    NODE_ENV: process.env.NODE_ENV
  };
  
  module.exports = {
    entry: [
      './src/index.js'
    ],
    output: {
      path: __dirname,
      publicPath: '/',
      filename: 'bundle.js'
    },
    module: {
      loaders: [
        {
          test: /\.jsx?$/,
          loader: 'babel-loader',
          exclude: /node_modules/,
          query: {
            cacheDirectory: true,
            presets: ['react', 'es2015', 'stage-1']
          }
        }
      ]
    },
    resolve: {
      extensions: ['', '.js', '.jsx']
    },
    devServer: {
      historyApiFallback: true,
      contentBase: './'
    },
    plugins: [
      new webpack.DefinePlugin({
        'process.env': JSON.stringify(envToBeInjected)
      }),
      new webpack.optimize.UglifyJsPlugin()
    ]
  };
  
subject: Revise webpack.config.js