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(); 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();}); 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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JavaScript

const express = require('express');
const app = express();

JavaScript

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

JavaScript

const express = require('express');
const app = express();
const port = 3000;

app.get('/', (req, res) => {
    res.send('Hello world!');
});

app.listen(port, () => {
    console.log(`Server listening at http://localhost:${port}`);
});

const express = require('express');
const app = express();
const port = 3000;

app.get('/', (req, res) => {
    res.send('Hello world!');
});

app.listen(port, () => {
    console.log(`Server listening at http://localhost:${port}`);
});

JavaScript

app.post('/submit', (req, res) => {
    res.send('Data Received');
});

app.post('/submit', (req, res) => {
    res.send('Data Received');
});

JavaScript

app.get('/', (req, res) => {
    res.send('Hello world!');
});

app.get('/', (req, res) => {
    res.send('Hello world!');
});

JavaScript

const axios = require('axios');

const serverUrl = 'http://localhost:3000';

// Making a GET request to the server's root endpoint
axios.get(serverUrl)
  .then(response => {
    console.log('Response from the server:', response.data);
  })
  .catch(error => {
    console.error('Error while making GET request:', error.message);
  });

const axios = require('axios');

const serverUrl = 'http://localhost:3000';

// Making a GET request to the server's root endpoint
axios.get(serverUrl)
  .then(response => {
    console.log('Response from the server:', response.data);
  })
  .catch(error => {
    console.error('Error while making GET request:', error.message);
  });

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}`);
});

JavaScript

const express = require('express');
const app = express();
const port = 3000;

app.get('/', (req, res) => {
    res.send('Hello world!');
});

app.listen(port, () => {
    console.log(`Server listening at http://localhost:${port}`);
});

JavaScript

app.post('/submit', (req, res) => {
    res.send('Data Received');
});

JavaScript

app.get('/', (req, res) => {
    res.send('Hello world!');
});

JavaScript

const axios = require('axios');

const serverUrl = 'http://localhost:3000';

// Making a GET request to the server's root endpoint
axios.get(serverUrl)
  .then(response => {
    console.log('Response from the server:', response.data);
  })
  .catch(error => {
    console.error('Error while making GET request:', error.message);
  });

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}`);
});