node-hot-loader

Node Hot Loader

Node Hot Loader is a small tool for Hot Module Replacement support for Node.js application development with webpack.

It based on sources of webpack-dev-middleware and webpack/hot/only-dev-server. Under the hood it uses webpack and babel, so you can use all you need configurations in config files for babel and webpack.

The most suitable use case for Node Hot Loader is hot-reloaded express application. Express application can contains API and frontend together, moreover frontend can use own HMR, e.g. React with React Hot Loader. See how to setup React HMR with Express in React Hot Loader docs. Thus, both the frontend and the server will be hot-reloadable.

Node Hot Loader also supports webpack config files written on ES2015+ (through babel). For using ES2015+ in webpack configuration you must provide .babelrc configuration file in project root directory.

Requirements

Tested with Node.js v7, but must work on previous versions.

Installation

npm install --save-dev node-hot-loader webpack

Usage

Usage: node-hot {options}

Options:
  -c, --config       Webpack config file. If not set then search webpack.config.js in root directory.

Usage example

node-hot --config webpack.config.server.js

You can use all configurations for webpack compiler which webpack supports.

The minimum required configuration:

Node Hot Loader adds all necessaries to webpack config if not present already (e.g. HotModuleReplacementPlugin), but it's require the minimum configuration in your webpack config file:

import fs from 'fs';

export default {
  // node-hot run the all entries in one child process.
  // And the all entries will be with HMR support.
  // Usually only one entry required for node application. 
  entry: {
    server: [
      './server/index',
    ],
  },

  output: {
    // Webpack can't find hot-update if output file is not directly in output.path.
    // For example, filename: 'js/[name].js' will not work.
    // However, I have no many tests for that.
    filename: '[name].js',
  },

  // Exclude node_modules from bundle manual
  // or use for instance webpack-node-externals package (https://github.com/liady/webpack-node-externals)
  externals: fs.readdirSync(paths.nodeModules.dirname)
      .filter(x => ['.bin'].indexOf(x) === -1)
      .reduce((modules, mod) => {
        modules[mod] = `commonjs ${mod}`;
        return modules;
      }, {}),
  
  // It may be necessary when your compiled app uses Webpack too, e.g. for frontend serving,
  //   because Webpack sets __dirname to '/'.
  // It may be some issues in your app, so sets __dirname to false can help you.
  // See https://github.com/webpack/webpack/issues/1599.
  node: {
    __dirname: false,
    __filename: false,
  },
};

Express Hot Reload Example

import app from './app'; // configuring express app, e.g. routes and logic
import DB from './services/DB'; // DB service


function startServer() {
  const httpServer = app.listen(app.get('port'), (error) => {
    if (error) {
      console.error(error);
    } else {
      const address = httpServer.address();
      console.info(`==> 🌎 Listening on ${address.port}. Open up http://localhost:${address.port}/ in your browser.`);
    }
  });

  // Hot Module Replacement API
  if (module.hot) {
    // Hot reload of `app` and related modules.
    let currentApp = app;
    module.hot.accept('./app', () => {
      httpServer.removeListener('request', currentApp);
      import('./app').then(m => {
        httpServer.on('request', m.default);
        currentApp = m.default;
        console.log('Server reloaded!');
      })
      .catch(err => console.error(err));
    });

    // Hot reload of entry module (self). It will be restart http-server.
    module.hot.accept();
    module.hot.dispose(() => {
      console.log('Disposing entry module...');
      httpServer.close();
    });
  }
}

// After DB initialized start server
DB.connect()
    .then(() => {
      console.log('Successfully connected to MongoDB. Starting http server...');
      startServer();
    })
    .catch((err) => {
      console.error('Error in server start script.', err);
    });

License

MIT

Changelog

1.2.0 (2017-10-12)

• 1.2.0 (4d4c47f)
• Choose target 'node' only for multiple configurations (9362cca)
• Update README.md (0fb08e5)

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