Getting Started with Node.js

Node.js allows developers to run JavaScript outside the browser. It is widely used for backend development, APIs, and server-side applications.

In this guide, you will learn how to install Node.js, test the installation, use the REPL, and create your first server.

---

Installing Node.js

To start using Node.js, first install it on your computer.

Steps:

1. Visit the official website:

https://nodejs.org

1. Download the LTS (Long Term Support) version

2. Run the installer and complete setup using default options

This installation works on:

• Windows

• macOS

• Linux

Important:

Node.js installation automatically includes:

• Node runtime

• npm (Node Package Manager)

---

Checking Installation Using Terminal

After installation, open your terminal or command prompt.

Check Node.js version:

node -v

Example output:

v20.x.x

Check npm version:

npm -v

If both commands show version numbers, installation is successful.

---

Understanding Node REPL

REPL stands for:

• Read

• Eval

• Print

• Loop

It is an interactive environment where you can run JavaScript directly from the terminal.

Start REPL:

node

Example:

> console.log("Hello")
Hello

Another example:

> 10 + 20
30

Exit REPL:

.exit

Why REPL is Useful:

• Test JavaScript quickly

• Practice small snippets

• Debug logic easily

---

Creating Your First JavaScript File

Create a new file named:

app.js

Add the following code:

console.log("Hello from Node.js");

---

Running Script Using Node Command

Open terminal in the project folder and run:

node app.js

Output:

Hello from Node.js

First Execution Flow:

app.js → Node Runtime → Code Executes → Output Appears

---

Node Execution Flow (Concept)

JavaScript File
      ↓
Node Runtime
      ↓
Executes Instructions
      ↓
Shows Result in Terminal

---

Writing a Hello World Server

Node.js includes a built-in module called http that allows you to create servers.

Example:

const http = require("http");

const server = http.createServer((req, res) => {
  res.end("Hello World");
});

server.listen(3000, () => {
  console.log("Server running on http://localhost:3000");
});

---

Running the Server

Save the file and run:

node app.js

Terminal Output:

Server running on http://localhost:3000

Now open your browser and visit:

http://localhost:3000

You will see:

Hello World

---

Script → Runtime → Output Flow

JavaScript File
      ↓
Node Runtime Starts
      ↓
Server Executes
      ↓
Browser Receives Response

---

Suggestions (Best Practices)

• Use the LTS version of Node.js

• Learn terminal basics alongside Node.js

• Understand REPL before building projects

• Practice running scripts multiple times

• Keep early examples simple

• Avoid frameworks like Express in the beginning

• Focus on understanding core Node.js behavior

---

Conclusion

• Node.js runs JavaScript outside the browser

• Installation includes both Node and npm

• REPL helps test JavaScript interactively

• Scripts are executed using the node command

• Node.js can create servers using built-in modules

Learning these basics builds a strong foundation for backend development with Node.js.

---