webpack.config.js

const path = require('path');
var webpack = require("webpack");

var plugins = []; // if using any plugins for both dev and production
var devPlugins = [
  new webpack.DefinePlugin({
    'process.env.NODE_ENV': JSON.stringify(process.env.NODE_ENV || 'development')
  })
]; // if using any plugins for development

var prodPlugins = [
  new webpack.DefinePlugin({
    'process.env.NODE_ENV': JSON.stringify(process.env.NODE_ENV || 'production'),
  }),
  // new webpack.optimize.UglifyJsPlugin({
  //   compress: {
  //     warnings: true
  //   }
  // })
];

plugins = plugins.concat(
  process.env.NODE_ENV === 'production' ? prodPlugins : devPlugins
);

module.exports = {
  context: __dirname,
  entry: './frontend/bootup.jsx',
  output: {
    path: path.resolve(__dirname, 'app', 'assets', 'javascripts'),
    filename: 'bundle.js'
  },
  resolve: {
    extensions: ['.js', '.jsx', '*']
  },
  module: {
    rules: [
      {
        test: /\.jsx?$/,
        exclude: /(node_modules)/,
        use: {
          loader: 'babel-loader',
          query: {
            presets: ['@babel/env', '@babel/react']
          }
        },
      }
    ]
  },
  devtool: 'source-map',
  plugins: [
    new webpack.DefinePlugin({
      'process.env.NODE_ENV': JSON.stringify(process.env.NODE_ENV || 'production')
    }),
  ],
  mode: 'production',
};