Building Micro Frontend with Express
In this chapter, we will explore the concept of Micro Frontends and how to implement them using Express.js as a backend server. Micro Frontends is an architectural style that breaks up a frontend application into smaller, manageable pieces, allowing teams to work independently on different parts of an application. This chapter will provide a comprehensive guide from basic concepts to advanced implementation, including practical examples.
Introduction to Micro Frontends
What are Micro Frontends?
Micro Frontends extend the concept of microservices to the frontend. Instead of having a single monolithic frontend application, the application is split into smaller, independent applications or modules that can be developed, deployed, and scaled independently. This allows different teams to work on different parts of the application without interfering with each other.
Benefits of Micro Frontends
- Independent Development: Teams can work on different micro frontends using different technologies or frameworks.
- Scalability: Each micro frontend can be scaled independently based on traffic.
- Improved Deployment: Micro frontends can be deployed independently, reducing the risk of deployment failures.
Setting Up the Environment
Prerequisites
Before we start building, ensure you have the following tools installed:
- Node.js: Make sure you have Node.js installed on your machine. You can download it from nodejs.org.
- npm: This usually comes with Node.js.
Creating a New Project
Create a new directory for your micro frontend application:
mkdir micro-frontend-example
cd micro-frontend-example
Initializing a New Node.js Project
Run the following command to create a new package.json file:
npm init -y
Installing Express
Install Express.js as our backend framework:
npm install express
Project Structure
Create the following directory structure:
micro-frontend-example/
│
├── backend/
│ ├── index.js
│
├── frontend/
│ ├── app1/
│ │ ├── index.html
│ │ └── main.js
│ ├── app2/
│ │ ├── index.html
│ │ └── main.js
│
└── package.json
Building the Backend with Express
Creating the Express Server
In the backend/index.js file, set up a basic Express server:
// backend/index.js
const express = require('express');
const path = require('path');
const app = express();
const PORT = process.env.PORT || 3000;
// Serve static files from the frontend directory
app.use('/app1', express.static(path.join(__dirname, '../frontend/app1')));
app.use('/app2', express.static(path.join(__dirname, '../frontend/app2')));
// Default route
app.get('/', (req, res) => {
res.send('Welcome to the Micro Frontend Application');
});
// Start the server
app.listen(PORT, () => {
console.log(`Server is running on http://localhost:${PORT}`);
});
Explanation of the Code
- express.static(): This middleware serves static files from the specified directory. We are serving files for two micro frontends:
app1andapp2. - Default Route: A simple route that returns a welcome message when accessing the root URL.
Running the Backend Server
Run the server using the following command:
node backend/index.js
Visit http://localhost:3000 in your browser to see the welcome message.
Building the Frontend Applications
Creating Micro Frontend Application 1
In the frontend/app1/index.html, create a simple HTML file
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Micro Frontend App 1</title>
</head>
<body>
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</html>
In the frontend/app1/main.js, add the following code:
// frontend/app1/main.js
console.log('Micro Frontend App 1 is loaded');
Creating Micro Frontend Application 2
In the frontend/app2/index.html, create another simple HTML file:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Micro Frontend App 2</title>
</head>
<body>
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In the frontend/app2/main.js, add the following code:
// frontend/app2/main.js
console.log('Micro Frontend App 2 is loaded');
Explanation of the Frontend Code
- HTML Structure: Each micro frontend has its own HTML file that contains a title and a script tag linking to its JavaScript file.
- JavaScript Logging: Each micro frontend logs a message to the console when loaded.
Accessing the Micro Frontends
Now that both the backend and frontend applications are set up, you can access them by navigating to the following URLs:
- Micro Frontend App 1: http://localhost:3000/app1
- Micro Frontend App 2: http://localhost:3000/app2
You should see the respective messages for each micro frontend in your browser.
Enhancing Communication Between Micro Frontends
To facilitate communication between micro frontends, we can use an event bus or a shared state management approach. For simplicity, we will demonstrate a basic event bus.
Creating a Simple Event Bus
Create an eventBus.js file in the root of your frontend directory:
// frontend/eventBus.js
const eventBus = {
events: {},
on(event, listener) {
if (!this.events[event]) {
this.events[event] = [];
}
this.events[event].push(listener);
},
emit(event, data) {
if (this.events[event]) {
this.events[event].forEach(listener => listener(data));
}
}
};
export default eventBus;
Using the Event Bus in Micro Frontend Apps
Update the main.js files of both applications to use the event bus for communication.
In frontend/app1/main.js:
// frontend/app1/main.js
import eventBus from '../eventBus.js';
console.log('Micro Frontend App 1 is loaded');
eventBus.on('paymentProcessed', (data) => {
console.log(`App 1 received payment processed event with data: ${data}`);
});
// Emit an event
setTimeout(() => {
eventBus.emit('paymentProcessed', { amount: 100 });
}, 2000);
In frontend/app2/main.js:
// frontend/app2/main.js
import eventBus from '../eventBus.js';
console.log('Micro Frontend App 2 is loaded');
eventBus.on('paymentProcessed', (data) => {
console.log(`App 2 received payment processed event with data: ${data}`);
});
Explanation of the Event Bus
- Event Bus: A simple implementation that allows different parts of the application to communicate via events.
- on() Method: Registers an event listener.
- emit() Method: Emits an event, triggering all registered listeners.
Testing the Event Bus
When you load Micro Frontend App 1, it will emit a paymentProcessed event after 2 seconds, which will be received by both Micro Frontend App 1 and Micro Frontend App 2, demonstrating intercommunication.
In this chapter, we explored the concept of Micro Frontends and how to implement them using Express.js as a backend server. We learned about the benefits of using Micro Frontends and how to create independent frontend applications that can communicate with each other through an event bus. Happy coding !❤️