Introduction to Express.js
Express.js is a popular and minimalist web application framework for Node.js. It simplifies the process of building web applications and APIs by providing a set of powerful features and tools. Express.js is open-source and has a large community, making it a preferred choice for web developers working with Node.js.
Installing Express.js
Before you can use Express.js, you need to set up a Node.js environment and have Node Package Manager (npm) installed. Follow these steps to install Express.js in your Node.js project:
mkdir my-express-app
cd my-express-app
npm init -y
npm install express
Creating a Basic Express.js Server
To create a basic Express.js server, follow these steps:
const express = require('express');
const app = express();
app.get('/', (req, res) => {
res.send('Hello, Express!');
});
const port = 3000;
app.listen(port, () => {
console.log(`Server is running on http://localhost:${port}`);
});
Handling Different Types of Routes
Handling POST Requests
To handle a POST request, you need to use the app.post method:
app.post('/api/data', (req, res) => {
// Process the incoming data from the request (req.body)
res.send('Data received successfully!');
});
Handling Route Parameters
Route parameters allow you to pass dynamic values in the URL. For example, to handle a request for a specific user ID, you can define a route like this:
app.get('/users/:id', (req, res) => {
const userId = req.params.id;
// Fetch user data from the database using the userId
res.send(`User with ID ${userId} found.`);
});
Handling Query Parameters
Query parameters are used to pass data to the server in the URL. To handle query parameters, use the
req.query object:
app.get('/search', (req, res) => {
const searchTerm = req.query.q;
// Perform a search based on the searchTerm
res.send(`Search results for: ${searchTerm}`);
});
Middleware in Express.js
Middleware functions are functions that have access to the request and response objects. They can be used to perform actions before a request reaches the route handler or after the response is sent. Middleware functions can be used for tasks like logging, authentication, error handling, etc.
Creating a Middleware Function
const myMiddleware = (req, res, next) => {
// Perform some actions here
console.log('Middleware executed.');
// Call next() to pass control to the next middleware or route handler
next();
};
// Implement middleware globally for all routes
app.use(myMiddleware);
Conclusion
Express.js is a powerful and flexible web application framework for Node.js. By following the steps outlined above, you can easily create a basic Express.js server, handle different types of routes, and use middleware to extend its functionality. With the proper use of Express.js, you can efficiently build robust web applications and APIs using Node.js.
