Install Express in Node JS

Last Updated: 22nd June, 2023

Introduction

Welcome to this lesson on installing and setting up Express.js! Express.js is a powerful and versatile web application framework that allows developers to build scalable and robust applications quickly and efficiently. However, before you can start using Express.js, you need to ensure that it is installed and set up correctly on your system. In this lesson, we will cover the basics of installing Node.js and npm, creating a new project, creating a server, setting up basic routing, serving static files, and more. By the end of this lesson, you will have a solid understanding of how to install and set up Express.js, and you will be ready to start building your own web applications. So let's get started!

Prerequisites to install Express.js

Before installing Express.js, there are a few prerequisites that need to be installed on your system:

1. Node.js: Express.js is built on top of Node.js, so you will need to have Node.js installed on your system. You can download the latest version of Node.js from the official website: https://nodejs.org/en/download/.
2. Package manager: You will need a package manager to install Express.js and its dependencies. The most popular package managers for Node.js are NPM and yarn. NPM is installed automatically when you install Node.js, but you can also install yarn by following the instructions on the official website: https://classic.yarnpkg.com/en/docs/install/.

Once you have Node.js and a package manager installed, you are ready to install Express.js.

Installation and setup

To install Express.js, you need to follow these steps:

1. Create a new Node.js project: Once Node.js is installed, open your terminal or command prompt and create a new folder for your project. Navigate to the project folder and run the following command to create a new Node.js project:

npm init

This command will create a package.json file for your project that will contain all the information about your project, including its dependencies.

2. Install Express.js: Now that your project is set up, you can install Express.js by running the following command in your terminal:

npm install express --save

This will install the latest version of Express.js and save it as a dependency in your package.json file.

Creating a small application

1. Create a new file in your project directory called index.js. This will be the main file for your Express.js application.
2. Add the following code to index.js to create a simple Express.js server:

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

app.get('/', function (req, res) {
  res.send('Hello World!');
});

app.listen(3000, function () {
  console.log('Example app listening on port 3000!');
});

3. Save the changes to index.js.
4. Start the Express.js server by running the following command in your terminal:

node index.js

5. Open your web browser and navigate to http://localhost:3000 . You should see the message "Hello World!" displayed in your browser.

Congratulations! You have successfully installed and set up Express.js. From here, you can begin building your own web applications using this powerful Node.js framework

The Working of Express JS

The working of Express.js can be summarized in the following steps:

1. Import the Express.js module and create an instance of the express object.

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

2. Define routes for handling incoming HTTP requests using the app.get(), app.post(), app.put(), and app.delete() methods. Each route takes a URL pattern and a callback function that is executed when the route is matched.

app.get('/', function(req, res) {
  res.send('Hello, World!');
});

3. Define middleware functions using the app.use() method. Middleware functions can be defined globally for the entire application or specific to a particular route.

app.use(function(req, res, next) {
  console.log('Request received at:', new Date());
  next();
});

4. Define a template engine using the app.set() method. This is optional but recommended if you plan to render dynamic HTML content on the server.

app.set('view engine', 'ejs');

5. Start the server using the app.listen() method, which listens for incoming HTTP requests on a specified port.

app.listen(3000, function() {
  console.log('Server started on port 3000');
});

Overall, Express.js provides a powerful and flexible framework for building web applications and APIs in Node.js. Its intuitive API, middleware functions, and template engine support make it a popular choice for web developers.

Conclusion

Congratulations on completing this lesson on installing and setting up Express.js! Remember, Express.js is a powerful and versatile framework that allows you to build scalable and robust applications quickly and efficiently. As you continue to learn and develop your skills, be sure to explore the many features and tools that Express.js has to offer. With a little practice and perseverance, you can create amazing web applications that meet the unique needs of your projects.