React Webpack env example

package.json

{
  "name": "webpack-demo",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "webpack",
    "build": "cross-env NODE_ENV=production webpack -p"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "emoji-green-heart": "^1.2.1"
  },
  "devDependencies": {
    "babel-core": "^6.17.0",
    "babel-loader": "^6.2.5",
    "babel-preset-es2015": "^6.16.0",
    "cross-env": "^3.1.1",
    "webpack": "^2.1.0-beta.25"
  }
}

webpack.config.js

const webpack = require('webpack');
const NODE_ENV = process.env.NODE_ENV || 'development';

module.exports = {
    entry: './main.js',
    output: {
         path: './build',
         filename: 'bundle.js'
    },
    watch: NODE_ENV === 'development',
    devtool: NODE_ENV === 'development' && 'eval-source-map',
    module: {
        loaders: [{
            test: /\.js$/,
            exclude: /node_modules/,
            loader: 'babel-loader'
        }]
    },
    plugins: [
        new webpack.DefinePlugin({
            'process.env': {
                'NODE_ENV': JSON.stringify(NODE_ENV)
            }
        })
    ]
};