Node.js

Node.js is a cross-platform, open-source JavaScript runtime environment that can run on Windows, Linux, Unix, macOS, and more. Node.js runs on the V8 JavaScript engine, and executes JavaScript code outside a web browser.

Node.js uses an asynchronous event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices. Upon each connection, the callback is fired, but if there is no work to be done, Node.js will sleep.

Official Website

npm

npm is the default package manager for Node.js and is written entirely in JavaScript. It is used for managing and sharing packages of code with other developers.

npm is the world’s largest Software Registry.

npm commands

npm init - Create a new package.json file (initialize a new project)
npm i <package_name> - Install a package (locally, folder node_modules will be created)
Running npm i will install all the dependencies listed in the package.json file
npm i -g <package_name> - Install a package globally
npm i -D <package_name> - Install a package as a development dependency
npm uninstall <package_name> - Uninstall a package
npm uninstall -g <package_name> - Uninstall a package globally
npm uninstall -D <package_name> - Uninstall a development dependency
npm run <script_name> - Run a script from the package.json file (e.g. npm run dev)
npm list - List all locally installed packages
npm list -g - List all globally installed packages
npm audit - Check for vulnerabilities in installed packages
npm audit fix - Fix vulnerabilities in installed packages
npm outdated - Check for outdated packages
npm update - Update all packages to the latest version

Installation and Usage

To install Node.js and npm, run the following command:

sudo apt-get install nodejs npm

To install a package, run the following command:

npm install <package_name>

Create Hello World Application

Simple console application that prints “Hello, World!” to the console.

mkdir hello-world - Create a new directory
cd hello-world - Change to the new directory
npm init -y - Create a new package.json file (-y flag will skip the questionnaire)
nano index.js - Create and open a new file
Add the following code to the file

console.log('Hello, World!');

node index.js - Run the file

Web application that prints “Hello, World!” to the browser.

nano server.js - Create a new file
Add the following code to the file

const http = require('http');
const hostname = '';
const port = 3000;

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Hello, World!\n');
});

server.listen(port, hostname, () => {
  console.log(`Server running at http://${hostname}:${port}/`);
});

node server.js - Run the file

Open a web browser and navigate to http://localhost:3000. You should see the message “Hello, World!”.

Express.js

Express.js is fast, unopinionated, minimalist web framework for Node.js It is used for building web applications and APIs.

Official Website

Installation and Usage

To install Express.js, run the following command:

npm install express

npm and node commands

npm init - Create a new package.json file (initialize a new project)
npm i <package_name> - Install a package
npme i -D <package_name> - Install a package as a development dependency
- npm i -D typescript ts-node nodemon @types/express @types/socket.io
npm run <script_name> - Run a script from the package.json file
- npm run dev - Run the script named “dev” from the package.json file
- npm run start - Run the script named “start” from the package.json file
node -v - Check the installed version of Node.js
node <file_name> - Run a JavaScript file (e.g. node index.js)