old_contents: var path = require('path');
  var webpack = require('webpack');
  var ExtractTextPlugin = require('extract-text-webpack-plugin');
  // multiple extract instances
  var extractCSS = new ExtractTextPlugin('[name].css');
  module.exports = [
    {
      entry: {
        app: './js/index.js',
        vendor: ['whatwg-fetch']
      },
      output: {
        path: '../app/assets/javascripts/webpack',
        filename: '[name].js'
      },
      module: {
        loaders: [{
          test: /\.(jsx|js)$/,
          exclude: /node_modules/,
          loader: 'babel-loader',
          query: {
            presets: ['es2015', 'react', 'stage-2']
          }
        }]
      },
      plugins:[
        // vendor.bundle.jsを入れてないものはエラーになる
        new webpack.optimize.CommonsChunkPlugin("vendor", "vendor.bundle.js"),
      ],
      resolve: {
        extensions: ['', '.js', '.jsx']
      },
      devServer: {
        // dev-serverのcontext root
        contentBase: 'public',
        port: 3001
      }
    },
    {
      entry: {
        app: './css/index.scss'
      },
      output: {
        path: '../app/assets/stylesheets/webpack',
        filename: '[name].css'
      },
      module: {
        loaders: [
          {
            test: /\.css$/,
            loader: extractCSS.extract(['css'])
          },{
            test: /\.scss$/,
            loader: extractCSS.extract(['css','sass'])
          }
        ]
      },
      plugins:[
        extractCSS
      ],
      resolve: {
        extensions: ['', '.css', '.scss']
      }
    }
  ]
  
new_contents: var path = require('path');
  var webpack = require('webpack');
  var ExtractTextPlugin = require('extract-text-webpack-plugin');
  // multiple extract instances
  var extractCSS = new ExtractTextPlugin('[name].css');
  module.exports = [
    {
      entry: {
        app: './js/index.jsx',
        vendor: ['whatwg-fetch']
      },
      output: {
        path: '../app/assets/javascripts/webpack',
        filename: '[name].js'
      },
      module: {
        loaders: [{
          test: /\.(jsx|js)$/,
          exclude: /node_modules/,
          loader: 'babel-loader',
          query: {
            presets: ['es2015', 'react', 'stage-2']
          }
        }]
      },
      plugins:[
        // vendor.bundle.jsを入れてないものはエラーになる
        new webpack.optimize.CommonsChunkPlugin("vendor", "vendor.bundle.js"),
      ],
      resolve: {
        extensions: ['', '.js', '.jsx']
      },
      devServer: {
        // dev-serverのcontext root
        contentBase: 'public',
        port: 3001
      }
    },
    {
      entry: {
        app: './css/index.scss'
      },
      output: {
        path: '../app/assets/stylesheets/webpack',
        filename: '[name].css'
      },
      module: {
        loaders: [
          {
            test: /\.css$/,
            loader: extractCSS.extract(['css'])
          },{
            test: /\.scss$/,
            loader: extractCSS.extract(['css','sass'])
          }
        ]
      },
      plugins:[
        extractCSS
      ],
      resolve: {
        extensions: ['', '.css', '.scss']
      }
    }
  ]
  
subject: rename to jsx