# Micro-frontend, Module Federation

## Building a Super App with React Native and Module Federation: A Step-by-Step Guide

Building a **super app** with **micro frontends** in React Native using **Module Federation** involves a combination of tools, strategies, and patterns. Module Federation, introduced in Webpack 5, enables sharing code between different applications (or micro frontends). In the context of React Native, you can achieve a similar architecture by combining Module Federation concepts with React Native-specific tools and strategies. Here's a step-by-step guide:

#### **1. Understand the Requirements**

* **Super App**: A unified app hosting multiple smaller apps (micro-apps) with their own independent development, deployment, and scaling.
* **Micro Frontends**: Breaking down your super app into smaller, self-contained modules that are independently deployable and maintainable.

***

#### **2. Tools and Libraries**

* **Webpack 5 with Module Federation**: Use for code splitting and sharing components across micro-apps.
* **React Native Web**: Bridges React Native components to the web, making them compatible with Module Federation.
* **Metro Bundler**: The React Native default bundler. You'll need to adjust its setup for federation.
* **Hermes or JSI**: Use JavaScript engines and bridging for efficient communication between modules.
* **React Navigation**: For seamless navigation between micro frontends.
* **Module Federation Tools**: Libraries like `@module-federation/native-federation`.

***

#### **3. Architecture**

1. **Super App Shell**:
   * Acts as a host container for micro frontends.
   * Manages shared services like authentication, global state, theming, and navigation.
   * Loads micro frontends dynamically using Module Federation.
2. **Micro Frontends**:
   * Self-contained React Native applications or features.
   * Expose components, screens, or services via Module Federation.
3. **Shared Components and Libraries**:
   * Reusable UI components, hooks, or utilities shared across micro frontends.

***

#### **4. Implement Module Federation**

1. **Setup Webpack for Module Federation**:

   * Configure Webpack in each micro frontend and the super app to expose/consume modules.

   Example `webpack.config.js` for a micro-frontend:

   ```javascript
   javascriptCopy codeconst { ModuleFederationPlugin } = require('webpack').container;

   module.exports = {
     // Other configurations
     plugins: [
       new ModuleFederationPlugin({
         name: 'MicroFrontend',
         filename: 'remoteEntry.js',
         exposes: {
           './SomeComponent': './src/components/SomeComponent',
         },
         shared: ['react', 'react-native'],
       }),
     ],
   };
   ```

   In the super app:

   ```javascript
   javascriptCopy codeconst { ModuleFederationPlugin } = require('webpack').container;

   module.exports = {
     plugins: [
       new ModuleFederationPlugin({
         name: 'SuperApp',
         remotes: {
           MicroFrontend: 'MicroFrontend@http://localhost:3001/remoteEntry.js',
         },
         shared: ['react', 'react-native'],
       }),
     ],
   };
   ```
2. **React Native Web for Compatibility**:

   * Add `react-native-web` to your micro frontends to make them compatible with Webpack.
   * Configure aliases in `webpack.config.js` for React Native dependencies.

   ```javascript
   javascriptCopy coderesolve: {
     alias: {
       'react-native$': 'react-native-web',
     },
   },
   ```

***

#### **5. Metro Bundler Configuration**

To use Module Federation with React Native’s Metro bundler:

* Consider using tools like **@module-federation/native-federation** to adapt Module Federation concepts to React Native.
* Update `metro.config.js` to work with federated modules.

Example:

```javascript
javascriptCopy codeconst { withMetro } = require('@module-federation/native-federation/metro');

module.exports = withMetro({
  projectRoot: __dirname,
});
```

***

#### **6. Navigation Integration**

* Use **React Navigation** to allow seamless navigation between micro frontends.
* Each micro frontend defines its own navigation stack but integrates with the super app shell.

Example:

```javascript
javascriptCopy codeconst AppShell = () => {
  return (
    <NavigationContainer>
      <Stack.Navigator>
        <Stack.Screen name="Home" component={HomeScreen} />
        <Stack.Screen
          name="MicroFrontend"
          getComponent={() => import('MicroFrontend/SomeScreen').then((mod) => mod.default)}
        />
      </Stack.Navigator>
    </NavigationContainer>
  );
};
```

***

#### **7. Shared State Management**

Use libraries like **Redux** or **Recoil** for shared global state across micro frontends. Use Webpack’s `shared` configuration to ensure dependencies are not duplicated.

***

#### **8. Deployment and Updates**

* Host micro frontends independently (e.g., on a CDN or a server).
* Use Module Federation to load the latest version dynamically, enabling incremental updates without redeploying the super app.

***

#### **9. Testing and Performance Optimization**

* Test each micro frontend independently.
* Optimize Webpack configurations for tree-shaking and efficient code splitting.
* Use tools like **React DevTools** and **Profiler** for debugging.

***

#### **10. Challenges to Address**

* **Performance**: Ensure seamless user experience with lazy loading and efficient communication.
* **Consistency**: Maintain UI and state consistency across micro frontends.
* **Compatibility**: Resolve issues between Metro and Webpack.

***

<figure><img src="https://3244021997-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FkyX4f2mLrTFIb2Dhfun0%2Fuploads%2F9HzsPuyKlZStbqzTlUvV%2Fe979c2b7-5a5c-4380-8e47-eaaa5155ade0.webp?alt=media&#x26;token=c49f3787-c529-4b82-8d93-25fd9e816a3e" alt=""><figcaption></figcaption></figure>

#### Example Repository

* Consider starting with this guide on Module Federation with React Native or a boilerplate that supports React Native and Webpack integration.