Setting Up a Basic Express.js Server

Introduction and Goals

Welcome to your first lesson in Back-End Engineering with Express.js! Today, we're going to dive into the world of server-side development, a critical component of any web application. By understanding and setting up a basic Express.js server, you'll unlock the door that allows user browsers and your web application to communicate. Express.js is a lightweight and efficient web application framework for Node.js that's loved by developers worldwide. It's perfect for building web applications and APIs, serving as the back-end part of the MEAN stack — namely MongoDB, Express.js, AngularJS, and Node.js . You'll get a lot of hands-on practice throughout this course. Remember, all the necessary libraries, like Express.js, are pre-installed on the CodeSignal IDE, so you don't need to worry about installation for now. By the end of this lesson, you will be able to set up an Express.js server from scratch, understand how it operates, and see it in action. Are you excited? Let's get started!

Getting to Know Express.js

Just as human societies cannot function without rules and structures, web development requires frameworks to organize code and streamline development. One such framework is Express.js, used for building web applications on top of Node.js . Node.js is a runtime environment that lets us execute JavaScript code on the server side. When you wrap this with Express.js, it becomes much more straightforward and elegant to handle HTTP requests, manage routes, and deal with middleware functionalities. Express.js is widely used on some of the internet's most popular websites, including IBM, Uber, and Twitter. This popularity is due to Express.js's flexibility, simplicity, and scalability. In real-world applications, Express.js simplifies tasks such as user authentication, data retrieval, and serving static files, making it a go-to solution for many developers. JavaScript const express = require('express'); const app = express(); In the example above, we first import the Express.js module using the require() function. We then create an instance of Express.js as an app by calling the express() function. This app object will be used to set up our server.

Express.js Syntax Basics

Like every language or framework, Express.js has its syntax. Luckily, Express.js's syntax is quite minimalistic, which makes it easy to use and understand. A commonly used feature in Express.js is the concept of middleware. Middleware functions 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. JavaScript app.use((req, res, next) => {console.log('Time:', Date.now()); next();}); In the example above, this middleware logs the time of the request to the console. Middleware is crucial in real-world apps for handling tasks like logging, user authentication, and parsing request bodies.

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Lesson Summary and Practice

Great job getting to this point! Today we've learned about the Express.js web application framework and the Node.js platform it's built upon. We have delved into the world of server-side development, exploring the Express.js syntax and setting up a basic server.

In this lesson, we covered how to set up a basic Express.js server, handle GET requests as well as POST requests, and use middleware.

You have seen how to listen for HTTP requests, serve responses, and interact with the server using your web browser. You now understand the concept of routes and know how to handle GET and POST requests on different routes, and how to interact with them using axios library.

Below is the full code of this lesson for reference:

JavaScript

// Importing the Express.js module
const express = require('express');

// Creating an instance of the Express.js app
const app = express();

// Defining the port that the server will listen on
const port = 3000;

// Middleware function to log the time of the request
app.use((req, res, next) => {
    console.log('Time:', Date.now());
    next();
});

// Defining a GET route handler for the root URL ('/')
app.get('/', (req, res) => {
    res.send('Hello world!');
});

// Defining a POST route handler for the '/submit' URL
app.post('/submit', (req, res) => {
    res.send('Data Received');
});

// Starting the server and making it listen for requests on the specified port
app.listen(port, () => {
    console.log(`Server listening at http://localhost:${port}`);
});

// Importing the Express.js module
const express = require('express');

// Creating an instance of the Express.js app
const app = express();

// Defining the port that the server will listen on
const port = 3000;

// Middleware function to log the time of the request
app.use((req, res, next) => {
    console.log('Time:', Date.now());
    next();
});

// Defining a GET route handler for the root URL ('/')
app.get('/', (req, res) => {
    res.send('Hello world!');
});

// Defining a POST route handler for the '/submit' URL
app.post('/submit', (req, res) => {
    res.send('Data Received');
});

// Starting the server and making it listen for requests on the specified port
app.listen(port, () => {
    console.log(`Server listening at http://localhost:${port}`);
});

Just like learning to ride a bike, the best way to understand servers and Express.js is to practice continuously. Upcoming exercises will allow you to hone these skills, enabling you to respond to different routes, manage varying request methods, and serve specific responses.

So, are we ready to get our hands on the code and lay the first stone toward becoming an Express.js pro? Let's hop on to the exercises!

Introduction and Goals

Getting to Know Express.js

Express.js Syntax Basics

Join the 1M+ learners on CodeSignal

Setting up a Basic Express.js Server

Interacting with the Server

Reviewing the Express.js Server Code

Running the Server

Using Axios for HTTP Requests

Real-world Application and Takeaways

Lesson Summary and Practice