Federate a Module

Module Federation is a concept that allows developers to share code between applications at run-time. It is a way of doing micro-frontends, but it can also be used to share code between applications that are not micro-frontends.

In the context of Module Federation, a module can be thought as any piece of code, functionally independent, that can be reused in different applications. It can be a component, a service, a library, a utility, etc.

In order to share a module, it must be federated. This means that the module must be configured to be shared, and the application that wants to use it must be configured to use it.

Nx includes first class support for Module Federation for React and Angular applications. This means that you can federate modules in your workspace with a few simple commands.

Assumption

With this recipe we assume that you have already created a workspace with at least one React or Angular Module Federation host application. If you haven't, you can follow the Create a Host Recipe.

Step 1: Create the module

We will create a module that exports a hello function. Since we are using Nx, we will create a library for this module.

Create a library

❯

nx generate @nx/js:library hello --unitTestRunner=jest

Update the hello.ts file with the following code:

hello/src/lib/hello.ts
export default function hello(): string {
  return 'Hello from Nx';
}

Update hello/ barrel file index.ts with the following code:

hello/src/index.ts
export { default } from './lib/hello';

Step 2: Federate the module

Now that we have created the module, we need to configure it to be federated.

❯

nx generate @nx/react:federate-module hello/src/index.ts --name=hello --remote=greeting

Remote does not exist

If the remote provided does not exist (in this instance greeting), Nx will create it for you.

This command will:

Adds a module entry to the greeting remote module federation config file.

greeting/module-federation.config.ts
import { ModuleFederationConfig } from '@nx/webpack';

const config: ModuleFederationConfig = {
  name: 'greeting',
  exposes: {
    './Module': './src/remote-entry.ts',
    './Hello': 'hello/src/index.ts', // <-- this line was added,
  },
};
export default config;

Adds a Typescript path mapping to the greeting/Hello module in your root TSConfig file.

/tsconfig.base.json
{
  "paths": {
    "greeting/Module": ["greeting/src/remote-entry.ts"],
    "greeting/Hello": ["hello/src/index.ts"] // <-- this line was added
  }
}

Step 3: Use the module

Update the host application to use the federated module.

host/module-federation.config.ts
import { ModuleFederationConfig } from '@nx/webpack';

const config: ModuleFederationConfig = {
  name: 'host',
  remotes: ['greeting'], //  <-- Ensure that greeting remote is listed here
};

export default config;

host/src/app/app.tsx
import hello from 'greeting/Hello';

export function App() {
  return <div>{hello()}</div>;
}

export default App;

If you are using Angular, you would update the application in a similar fashion to use the federated module.

Step 4: Run the application

Just run the application as usual.

❯

nx serve host

To start the application, use the following address: http://localhost:4200. Once opened, you'll see the message "Hello from Nx". This message is loaded from the greeting remote, which runs on port 4201.