Introduction to Express.js
Express.js, commonly referred to as Express, is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It's designed to build web applications and APIs quickly and efficiently.
Key Features of Express:โ
Routing: Express makes it easy to define routes for your application. Routes are used to map specific HTTP methods and URLs to functions that handle them.
Middleware: Middleware functions are a powerful feature of Express. They can be used to perform tasks before the request reaches its final handler. This can include tasks like authentication, logging, and data parsing.
Templating: Express allows you to use various template engines like EJS, Pug, or Handlebars to dynamically generate HTML.
Static Files: You can serve static files (like HTML, CSS, and JavaScript) using Express, making it ideal for building single-page applications and static websites.
Error Handling: Express provides a clean and effective way to handle errors in your application.
Installing Expressโ
Before you can use Express, you need to install it. You can install Express using npm (Node Package Manager). Open your terminal and run:
npm install express
Creating a Simple Express Applicationโ
Let's create a basic Express application and see how it works. First, create a file, for example, app.js
. Then, add the following code:
const express = require('express');
const app = express();
const port = 3000;
// Define a route
app.get('/', (req, res) => {
res.send('Hello, Express!');
});
// Start the server
app.listen(port, () => {
console.log(`Server is running on port ${port}`);
});
In this example, we:
- Import the Express module.
- Create an Express application.
- Define a route for the root URL ('/').
- Use the
app.get
method to handle HTTP GET requests. - Send a response of "Hello, Express!" when someone accesses the root URL.
- Start the server on port 3000.
To run this application, use the following command:
node app.js
Now, if you open a web browser and go to http://localhost:3000
, you'll see "Hello, Express!" displayed in your browser.
Hello, Express!
This is a simple example, but it demonstrates the basics of creating an Express application and defining routes. You can build on this foundation to create more complex web applications and APIs.