👉 Overview
👀 What ?
NodeJS Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It is known for its efficiency and lightweight nature, making it ideal for building fast, scalable network applications.
🧐 Why ?
Express is essential because it acts as a middleware to manage everything, from routes to handling requests and views. It simplifies the process of writing server code, eliminating the need to worry about low-level protocols, threads, and processes. It is also extremely flexible and pluggable, allowing developers to choose from a wide array of plugins to add additional functionality. This makes it a popular choice for web application development.
⛏️ How ?
To implement Express, you first need to install Node.js and npm (Node Package Manager). After that, you can simply install Express using npm with the command 'npm install express'. To create an Express application, you need to require Express in your file, create an instance of Express, define routes, and finally start the server using app.listen().
⏳ When ?
NodeJS Express began to be widely used in web development soon after its release in 2010 due to its simplicity, speed, and minimalism.
⚙️ Technical Explanations
Express.js is a web application framework for Node.js. It is designed for building web applications and APIs. It is the standard server framework for Node.js and is known for its simplicity, flexibility, and scalability.
At its core, Express.js operates on top of Node.js, a platform that uses Chrome's JavaScript runtime. This allows it to provide HTTP utility methods and middleware, creating a robust API both quickly and easily. This makes Express.js ideal for building efficient web applications.
One of the key features of Express.js is its use of middleware. Middleware are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle. The next middleware function is often represented by a variable named 'next'. Middleware can execute any code, alter the request and the response objects, end the request-response cycle, or call the next middleware function in the stack.
The middleware functions in Express.js operate in a stack-like manner. When a request is received, it is passed from one middleware function to the next, each function performing some operation on the request or response. If a middleware function does not end the request-response cycle, it must call 'next()' to pass control to the next middleware function in the stack. If it fails to call 'next()', the request will be left hanging, and the client will not receive a response.
Express.js also provides a routing table which is used to perform different actions based on the HTTP method and URL. This allows developers to define routes based on the requirements of the application.
Furthermore, Express.js is highly customizable and allows developers to choose from a wide array of plugins to add additional functionality. This makes it a popular framework for web application development.
In summary, Express.js is a powerful, efficient, and flexible framework for Node.js. Its use of middleware, HTTP utility methods, and routing makes it an ideal choice for building robust web applications and APIs.
Let's demonstrate a simple Express.js application:
- Install Node.js and npm: Before you can start using Express.js, you need to have Node.js and npm (Node Package Manager) installed on your computer. If they're not installed, you can download and install them from https://nodejs.org/.
- Install Express.js: Once Node.js and npm are installed, open your terminal and install Express.js using npm with the command
npm install express. - Create a new file: Create a new file named
app.jsin your project directory. - Setting up an Express.js application: In the
app.jsfile, start by requiring Express.js and create an instance of Express:
const express = require('express');
const app = express();
- Define a route: Let's define a simple route that will respond with "Hello World" when someone visits the root ('/') of our application:
app.get('/', function(req, res) {
res.send('Hello World!');
});
In this code, app.get() is a method that tells the server to respond with 'Hello World!' when a GET request is made to the homepage. The req (request) and res (response) are objects that provide information and functionality for HTTP requests and responses respectively.
- Start the server: We can start our server to listen on, for example, port 3000:
app.listen(3000, function() {
console.log('App is listening on port 3000!');
});
This code tells the server to listen for requests on port 3000 and logs a message to the console once the server is ready.
- Run the application: Save your
app.jsfile. In your terminal, navigate to your project directory and run the application using Node.js with the commandnode app.js. You should see the message 'App is listening on port 3000!'. Open a web browser and navigate tohttp://localhost:3000. You should see the message 'Hello World!'.
This is a very basic example of an Express.js application. Express.js allows for much more complex applications with multiple routes, middleware, and more.