webpack.demo.config.js

var webpack = require('webpack');

module.exports = {
  plugins: [
    new webpack.DefinePlugin({
      'process.env': {
        'NODE_ENV': JSON.stringify('production')
      }
    })
  ],
  module:  {
    rules: [
      { test: /\.jsx?$/, use: 'babel-loader', exclude: /node_modules/ },
      { test: /\.json$/, use: 'json-loader',  exclude: /node_modules/ }
    ]
  }
};