The arrival of Express.js v5 marks a decade of development!

Express.js has been a popular web application framework for Node.js for over a decade, and now it has finally released its latest version, v5. This new version comes with some major improvements and changes that make it even more powerful and flexible. In this tutorial, we will walk you through the new features and changes in Express.js v5 and show you how to get started with this latest version.

1. Installation
   To install Express.js v5, you can use npm, the Node.js package manager. Open your terminal and run the following command:

npm install express@next

This will install the latest version of Express.js, which is currently v5. You can also specify the exact version by running:

npm install express@5.0.0-alpha.1

1. Major Changes
   Express.js v5 comes with some major changes and improvements, including:

• Removal of the built-in middleware: In previous versions of Express.js, there were built-in middleware functions that were automatically added to every route. In v5, these middleware functions have been removed, and you need to explicitly add them to your routes if you want to use them.
• Improved error handling: Error handling has been restructured in v5, making it easier and more flexible to handle errors in your application.
• Enhanced routing capabilities: The routing system in Express.js has been improved in v5, allowing for more complex and flexible routing configurations.

1. Getting Started
   To get started with Express.js v5, create a new Node.js project and install Express.js using npm as described in the installation section above. Create a new file called app.js and add the following code to set up a basic Express.js server:

const express = require('express');
const app = express();
const port = 3000;

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`);
});

Run the following command in your terminal to start the server:

node app.js

You should see a message in the terminal saying "Server running at http://localhost:3000". Open your web browser and navigate to http://localhost:3000 to see the "Hello World!" message displayed on the page.

1. Express.js Middleware
   Middleware functions are at the core of Express.js, allowing you to intercept and modify incoming requests and outgoing responses. In Express.js v5, you need to explicitly add middleware functions to your routes. Here’s an example of how to add a middleware function to a route:

const express = require('express');
const app = express();
const port = 3000;

// Custom middleware function
app.use((req, res, next) => {
  console.log('Middleware function triggered');
  next();
});

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`);
});

In the example above, the custom middleware function is added using app.use() and will be triggered for every incoming request. You can also add middleware functions to specific routes using app.use('/myroute', myMiddleware).

1. Error Handling
   Error handling in Express.js v5 has been improved and restructured to make it easier to handle and manage errors in your application. You can use the next() function to pass errors to the error handling middleware, as shown in the example below:

const express = require('express');
const app = express();
const port = 3000;

app.get('/', (req, res) => {
  const error = new Error('Error message');
  next(error);
});

app.use((err, req, res, next) => {
  res.status(500).send('Internal Server Error');
});

app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`);
});

In the example above, an error is created within the route handler, and then passed to the error handling middleware using next(error). The error handling middleware then responds with a 500 status code and an error message.

1. Conclusion
   Express.js v5 brings significant improvements and changes to the popular web application framework for Node.js. The removal of built-in middleware, improved error handling, and enhanced routing capabilities make Express.js even more powerful and flexible. This tutorial has shown you how to get started with Express.js v5 and use some of its new features. Express.js v5 is definitely worth exploring for both new and existing Express.js developers.