Angular 16 Micro Frontend - Step by step

Micro frontends is an architectural approach that involves breaking down a frontend monolith into smaller, more manageable parts or micro-applications. Each micro-frontend is responsible for a specific feature or functionality of the application, and they can be developed and deployed independently. Angular, being a popular JavaScript framework for building web applications, can also be used to implement micro frontends. Here are some key concepts and strategies for implementing micro frontends with Angular:

• Module Federation: Module Federation is a technique introduced by the Webpack team that allows you to load independently developed and deployed Angular modules (micro-frontends) into a host application. With Module Federation, you can share dependencies, dynamically load remote modules, and compose your application from multiple micro-frontends.

• Angular Elements: Angular Elements is a feature of Angular that allows you to package Angular components as standalone custom elements (web components). This enables you to use these components in different applications, including non-Angular applications, which can be a part of your micro-frontend architecture.

• Routing: Micro frontends often need to handle routing independently. Angular's router can be used to manage the routing within each micro-frontend. Each micro-frontend can define its routes and handle navigation within its scope.

• Communication: Communication between micro-frontends and the host application or between different micro-frontends can be achieved through various methods such as custom events, HTTP requests, or a shared state management system like Redux or NgRx.

• Shared Libraries: To ensure consistency and reduce duplication, you can create shared libraries that contain common components, services, or utilities used across multiple micro-frontends.

• Versioning and Deployment: Managing versions and deployments of individual micro-frontends is a critical aspect of this architecture. Each micro-frontend should have its own versioning and deployment process, allowing for independent updates.

• Lazy Loading: Take advantage of Angular's lazy loading capabilities to load micro-frontends on-demand, reducing the initial load time of your application.

• Container Application: The host application or container application is responsible for loading and orchestrating the various micro-frontends. It provides the shell or layout for the micro-frontends to be displayed within.

• Error Handling: Implement error handling strategies to gracefully handle failures in individual micro-frontends without impacting the overall user experience.

• Testing: Develop testing strategies that encompass both unit testing for individual micro-frontends and integration testing to ensure the entire application works as expected.

Remember that while micro frontends can provide benefits in terms of development and scalability, they also introduce complexity. It's essential to carefully plan your architecture, versioning, and communication strategies to make the most of this approach. Additionally, tools and best practices may have evolved since my last update in September 2021, so it's a good idea to consult the Angular documentation and community resources for the latest guidance on implementing micro frontends with Angular.

Creating a complete Angular micro-frontend application involves several steps and components. I'll provide you with a high-level outline of how to structure such an application. Keep in mind that building a full-fledged micro-frontend architecture can be complex and may require in-depth knowledge of Angular, Webpack, and module federation. Here's a simplified example to get you started: 1. **Create Angular Micro-Frontend Projects**: Start by creating multiple Angular projects, each representing a micro-frontend. You can use the Angular CLI to generate these projects:

ng new micro-frontend1
ng new micro-frontend2
# Create as many micro-frontends as needed

2. **Develop Micro-Frontends**: In each micro-frontend project, develop Angular components, services, and routing specific to that micro-frontend's functionality. For example, create `Component1` in the first micro-frontend and `Component2` in the second one. 3. **Expose Micro-Frontends as Web Components**: To make your Angular components usable in different applications, convert them into web components using Angular Elements. You'll need to create a separate module for each web component and define a custom element for it. Here's a simplified example:

// app.module.ts in a micro-frontend project
import { NgModule, Injector } from '@angular/core';
import { createCustomElement } from '@angular/elements';
import { Component1Component } from './component1.component';

@NgModule({
  declarations: [Component1Component],
  entryComponents: [Component1Component],
})
export class AppModule {
  constructor(private injector: Injector) {}

  ngDoBootstrap() {
    const el = createCustomElement(Component1Component, { injector: this.injector });
    customElements.define('micro-frontend1', el);
  }
}

4. **Build and Package Web Components**: Build each micro-frontend project and package the resulting web components into separate JavaScript bundles. You can use the Angular CLI or Webpack for this purpose. Make sure to generate `.js` files that can be loaded independently in other applications. 5. **Set Up Module Federation**: In your container application (the application that will host the micro-frontends), configure Webpack with Module Federation to load the micro-frontends dynamically. This involves specifying the remote entry points for each micro-frontend.

// webpack.config.js in the container application
const ModuleFederationPlugin = require('webpack/lib/container/ModuleFederationPlugin');

module.exports = {
  // ...
  plugins: [
    new ModuleFederationPlugin({
      name: 'container',
      remotes: {
        microfrontend1: 'microfrontend1@http://path-to-microfrontend1.com/remoteEntry.js',
        microfrontend2: 'microfrontend2@http://path-to-microfrontend2.com/remoteEntry.js',
      },
    }),
  ],
};

6. **Container Application**: Create an Angular application (container) that will host the micro-frontends. This application should include routing and a layout to display the micro-frontends. Use Angular router to load the micro-frontends dynamically based on the user's navigation. 7. **Integrate Micro-Frontends**: In the container application's templates, use custom elements to integrate the micro-frontends. For example:

<app-root>
  <!-- Load Micro-Frontends using custom elements -->
  <micro-frontend1></micro-frontend1>
  <micro-frontend2></micro-frontend2>
</app-root>

8. **Routing and Navigation**: Implement routing in the container application to navigate between different micro-frontends. You can use Angular's router for this purpose, and each route can correspond to a specific micro-frontend. 9. **Testing and Deployment**: Test each micro-frontend independently, and also test the container application's integration of micro-frontends. Deploy the micro-frontends separately, and ensure that the container application can load them from their remote locations. 10. **Error Handling and State Management**: Implement error handling strategies to handle failures in loading or communicating with micro-frontends. Consider using state management libraries like NgRx for shared state between micro-frontends. Please note that this is a simplified example, and building a production-ready micro-frontend architecture can be much more complex. You'll need to consider aspects like versioning, security, and performance optimization as well. Additionally, tooling and best practices may have evolved since my last update in September 2021, so consult the Angular documentation and relevant community resources for the latest guidance on implementing micro frontends with Angular.