Node.js is a runtime environment that lets you run JavaScript code outside the browser — for example, on your computer or server. It uses the V8 JavaScript engine (the same engine in Google Chrome) to execute code quickly.

⚙️ Key Features of Node.js

✅ Non-blocking, event-driven I/O: Handles many connections at once without waiting for each to finish (great for real-time apps).

✅ Single-threaded, but can handle concurrency: Uses an event loop to manage asynchronous tasks efficiently.

✅ npm (Node Package Manager): Comes with a massive ecosystem of reusable libraries.

✅ Cross-platform: Runs on Windows, Mac, and Linux.

🔥 What is Node.js Used For?

• Web servers (e.g., Express.js apps)
• REST APIs and GraphQL APIs
• Real-time apps (e.g., chat, online games)
• Command-line tools
• Microservices
• Proxies, middleware, and more

To run a JavaScript file using Node.js, you just open your terminal, navigate to the folder containing your .js file, and type: node filename.js

What is Node.js LTS?

• LTS stands for Long-Term Support.
• An LTS release of Node.js is a version guaranteed by the Node.js team to receive active support (bug fixes, new features) for 18 months and maintenance (critical fixes, security patches) for an additional 12 months after that.
• LTS versions are labeled with codenames (e.g., Node 18 “Gallium”).
• Non-LTS releases (sometimes called "Current") only get short-term support and are mainly for trying out the latest features.

Why prefer LTS?

✅ Stability – LTS versions are tested extensively and avoid breaking changes, so they’re reliable for production use.

✅ Security – LTS versions receive critical security patches, keeping your application protected.

✅ Ecosystem Compatibility – Popular packages and frameworks (like React, Angular, Express) tend to support LTS versions first, ensuring fewer compatibility issues.

✅ Longer Support – With up to 3 years of support, you don’t have to upgrade frequently, which reduces maintenance overhead.

In summary: For production environments, always choose the latest LTS release to ensure stability, security, and smoother development.

Package and module

Packages: In Node.js, a package is a reusable piece of code — often a library or tool — that you can install into your project to avoid reinventing the wheel. Packages are how you share, reuse, and manage code in the Node ecosystem.

Modules: A module is a reusable block of code — either built-in or custom — that encapsulates related functions, objects, or logic. In Node.js, modules help organize code by splitting it into separate files that can be imported using require or import. Node provides built-in core modules (like fs, http, path) as part of its runtime, which let you perform essential tasks without needing to install anything from npm.

✅ A module is a single file or folder with code you can import (like require('./myModule.js')).

✅ A package is a collection of one or more modules bundled together, usually with a package.json file describing them. Packages are what you install from npm.

• Every package contains at least one module (that’s what makes it usable),
• But not every module is a package — your local myModule.js file is a module, but it’s not a package unless you add a package.json.
• A module is an individual building block (e.g., one JavaScript file with reusable code).
• A package is a box that can contain one or many modules, along with metadata (name, version, dependencies) — making it easy to share and install.

Key difference:

• A package is the bigger, distributable unit — it may contain many modules.
• A module is an individual file (or sometimes a folder acting as a module) you can import into your code.

What does npm init -y do?

• It quickly creates a package.json file in your current directory.
• The y flag means “yes to all defaults” — so npm skips asking you questions like project name, version, description, entry point, author, etc.
• Instead, it fills in package.json with default values, using your folder name as the project name.

🔸 Scenario 1: You run npm install some-package

🔸 Scenario 2: You run npm install without specifying a package

Key files and folders created/used

Common sections in package.json