Express.js

Introduction

Express.js is a popular, fast, and lightweight web application framework for Node.js. It provides a set of robust features for developing web and mobile applications. With Express.js, it is easy to build both server-side and client-side components with powerful APIs and an efficient routing system.

Features

Express.js comes with a set of powerful features:

Routing

Express.js provides an efficient and easy-to-use routing system. With the routing system, you can easily define routes using HTTP methods (GET, POST, PUT, etc.) and send responses based on different URLs.

Here's an example of defining a simple route:

app.get('/products', (req, res) => {
  res.send('All products');
});

Middleware

Middleware functions in Express.js are used to handle incoming requests and outgoing responses. Express.js provides a set of built-in middleware functions, and it is easy to create custom middleware.

Here's an example of a custom middleware function:

app.use((req, res, next) => {
  console.log('Time:', Date.now());
  next();
});

Templating Engines

With Express.js, you can easily render HTML templates using various templating engines such as EJS, Pug, and Handlebars. Templating engines allow you to write dynamic HTML content easily.

Here's an example of using the EJS templating engine:

app.set('view engine', 'ejs');
app.get('/users', (req, res) => {
  res.render('users', { title: 'Users', users: [ { name: 'Alice' }, { name: 'Bob' } ] });
});

Error Handling

Express.js provides a built-in error handling mechanism. You can define error handling middleware functions to catch and handle errors that occur during the execution of the application.

Here's an example of error handling middleware:

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

Conclusion

Express.js is a powerful and popular web application framework for Node.js. With its efficient routing system, middleware functions, templating engines, and error handling mechanism, it makes web development easy and fast.