webpack.config.js

var path = require('path'),
    webpack = require('webpack'),
    merge = require('webpack-merge');

const TARGET = process.env.npm_lifecycle_event;
const PATHS = {
  src: path.join(__dirname, 'src'),
  dest: path.join(__dirname, 'dist')
}
const common = {
  entry: PATHS.src + '/main',
  resolve: {
    extensions: ['', '.js', '.jsx']
  },
  module: {
    loaders: [
      {
        test: /\.jsx$/,
        include: PATHS.src,
        loader: 'babel'
      }
    ]
  }
}

if(TARGET === 'start' || !TARGET) {
  module.exports = merge(common, {
    devServer: {
      contentBase: PATHS.src,
      port: 8000,
      historyApiFallback: true,
      hot: true,
      inline: true,
      progress: true,
      stats: 'errors-only'
    },
    plugins: [
      new webpack.HotModuleReplacementPlugin()
    ]
  });
}

if(TARGET === 'build') {
  module.exports = merge(common, {
    output: {
      path: PATHS.dest,
      filename: 'bundle.js'
    }
  });
}