webpack.config.js

var path = require("path");
var webpack = require("webpack");
var plugins = [];

var prodPlugins = [
  new webpack.DefinePlugin({
    'process.env': {
      'NODE_ENV': JSON.stringify('development')
    }
  })
];

plugins = plugins.concat( prodPlugins );

module.exports = {
  context: __dirname,
  entry: "./frontend/envent.jsx",
  output: {
    path: path.resolve(__dirname, 'app', 'assets', 'javascripts'),
    filename: "bundle.js"
  },
  plugins: plugins,
  module: {
    loaders: [
      {
        test: [/\.jsx?$/, /\.js?$/],
        exclude: /node_modules/,
        loader: 'babel-loader',
        query: {
          presets: ['es2017', 'react']
        },
      },
      {
        test: /\.css$/,
        use: [ 'style-loader', 'css-loader' ]
      },
    ],
  },
  devtool: 'source-map',
  resolve: {
    extensions: [".js", ".jsx", "*"]
  }
};