Introduction to Node.js for Beginners

What is Node.js

Node.js is a runtime environment that allows you to run JavaScript outside a web browser. It is commonly used for backend development to build fast and scalable server-side applications.

Why Use Node.js

Uses JavaScript for both frontend & backend
Fast and scalable due to its non-blocking architecture
Has a huge library of open-source packages (NPM)
Used by big companies like Netflix, PayPal, and LinkedIn

Installing Node.js

Step 1: Download & Install

Go to nodejs.org
Download the LTS (Long-Term Support) version
Install it (Make sure NPM is included)

Step 2: Check Installation

Open Command Prompt (Windows) or Terminal (Mac/Linux) and type:

node -v

This should show the installed version of Node.js.

To check NPM (Node Package Manager):

NPM -v

Creating Your First Node.js App

1. Create a Project Folder

Open the terminal and run:

mkdir my-node-app CD my-node-app

2. Initialize a Node.js Project

npm init -y

This creates a package.json file, which manages dependencies and configurations.

3. Creating a Simple Server

Create a file called server.js and open it in a code editor (e.g., VS Code).

Write this code in server.js

const http = require("http");

const server = http.createServer((req, res) => {

res.writeHead(200, { "Content-Type": "text/plain" });

res.end("Hello, Node.js Server!");

});

server.listen(3000, () => {

console.log("Server is running on port 3000");

});

const http = require("http");
const server = http.createServer((req, res) => {
  res.writeHead(200, { "Content-Type": "text/plain" });
  res.end("Hello, Node.js Server!");
});

server.listen(3000, () => {
  console.log("Server is running on port 3000");
});

4. Run the Server

terminal, run:

node server.js

5. Test Your Server

http://localhost:3000

You should see “Hello, Node.js Server!”

Using Express.js (Framework)

Express.js is a popular framework for building web applications.

1. Install Express

npm install express

2. Create an Express Server (server.js)

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

app.get("/", (req, res) => {

res.send("Hello from Express.js!");

});

app.listen(3000, () => {

console.log("Server running on port 3000");

});

const express = require("express");const app = express(); app.get("/", (req, res) => { res.send("Hello from Express.js!"); }); app.listen(3000, () => { console.log("Server running on port 3000"); });

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

app.get("/", (req, res) => {
  res.send("Hello from Express.js!");
});

app.listen(3000, () => {
  console.log("Server running on port 3000");
});

3. Start the Express Server

node server.js

http://localhost:3000

“Hello from Express.js!”

Requests:

The request is coming from the client side, and the user wants a response from the server to act on. These actions may be non-blocking, simple, or they may block complex tasks.

Node.js Server:

Node.js is used on the server side. It takes the incoming client requests from the users, processes the requests, and responds to that particular client or user.

Event Queue:

The Node.js event queue stores the requests and passes them one by one into the event loop.

Event Loop:

The event loop receives the request from the event queue, processes the request, and returns the response to the particular client.

Thread Pool:

The thread pool consists of the available threads in our Node.js server, which will take some tasks to complete the client request.

External Resources:

External resources are those that need to fulfill the blocking operations in client requests. These resources can be for computation, data storage, etc.