old_contents: import path from 'path';
  import webpack from 'webpack';
  import CommonsChunkPlugin from 'webpack/lib/optimize/CommonsChunkPlugin';
  
  const PROD = process.env.NODE_ENV || 0;
  
  module.exports = {
    devtool: PROD ? false : 'eval',
  
    entry: {
      app: './app/assets/scripts/App.js',
      vendor: [
        'picturefill',
        './app/assets/_compiled/modernizr'
      ]
    },
  
    output: {
      path: __dirname + '/app/assets/_compiled',
      publicPath: '/assets/_compiled/',
      filename: '[name].js',
      chunkFilename: '_chunk/[name]_[chunkhash].js'
    },
  
    plugins: [
      new webpack.optimize.UglifyJsPlugin({
        compress: PROD ? true : false,
        output: {
          comments: false
        }
      }),
  
      new CommonsChunkPlugin({
        children: true,
        minChunks: 2
      })
    ],
  
    module: {
      loaders: [
        {
          test: /\.js$/,
          exclude: /node_modules/,
          loader: 'babel-loader'
        }
      ]
    }
  };
  
new_contents: import path from 'path';
  import webpack from 'webpack';
  import CommonsChunkPlugin from 'webpack/lib/optimize/CommonsChunkPlugin';
  
  const PROD = process.env.NODE_ENV || 0;
  
  module.exports = {
    devtool: PROD ? false : 'eval-cheap-module-source-map',
  
    entry: {
      app: './app/assets/scripts/App.js',
      vendor: [
        'picturefill',
        './app/assets/_compiled/modernizr'
      ]
    },
  
    output: {
      path: __dirname + '/app/assets/_compiled',
      publicPath: '/assets/_compiled/',
      filename: '[name].js',
      chunkFilename: '_chunk/[name]_[chunkhash].js'
    },
  
    plugins: [
      new webpack.optimize.UglifyJsPlugin({
        compress: PROD ? true : false,
        output: {
          comments: false
        }
      }),
  
      new CommonsChunkPlugin({
        children: true,
        minChunks: 2
      })
    ],
  
    module: {
      loaders: [
        {
          test: /\.js$/,
          exclude: /node_modules/,
          loader: 'babel-loader'
        }
      ]
    }
  };
  
subject: Improve source maps for JS