1) Node Introduction

1. Basic Introduction
   Node.js is a runtime environment that allows you to run JavaScript outside the browser, typically on the server.
   It’s built on Google Chrome V8 Engine, which compiles JavaScript into fast machine code.
   Node.js lets you use JavaScript to build backend services, APIs, real-time apps, and scalable network applications.
   i) Installation of Node.js
   a) On distributions that support apt package manager, you can install Node.js with the following commands,

   sudo apt update
   sudo apt install nodejs
   sudo apt install npm
   

   b) Verify Installation
   Open your command line tool (Command Prompt, Terminal, etc.).
   Type node -v to see the Node.js version installed.
   Type npm -v to see the npm (Node Package Manager) version installed.

   When to Use Node.js
   Best for: REST APIs Real-time apps (chat, notifications), Streaming apps, Microservices architecture
   Avoid for: Heavy CPU processing Complex multi-threaded enterprise systems

2. How node js Works
   Node.js uses an event-driven, non-blocking I/O model, which is very different from traditional server models.
   i) Single-threaded Event Loop
   Node.js runs on a single main thread
   Uses an event loop to handle multiple requests efficiently
   ii) Non-blocking I/O
   Operations like file reading, DB calls, API requests are asynchronous
   Instead of waiting, Node.js continues executing other tasks
   iii) Event Loop Flow
   Request comes in
   If it’s a simple task → handled immediately
   If it’s I/O (DB, file, API): Sent to background workers (libuv thread pool)
   Node.js continues handling other requests
   Once the task completes → callback/promise is executed
   Here High concurrency with low resource usage

3. Advantages of Node.js
   i) High Performance
   Powered by V8 engine
   Fast execution due to JIT compilation
   ii) Non-blocking & Scalable
   Handles thousands of concurrent connections efficiently
   Ideal for: Real-time apps (chat, gaming), Streaming apps, APIs
   iii) Same Language (JavaScript Everywhere)
   Frontend + Backend both use JavaScript
   Easier for full-stack developers
   iv) Huge Ecosystem
   npm provides millions of packages
   v) Great for Microservices
   Lightweight and fast startup Easy to scale horizontally
   vi) Real-time Capabilities
   Works well with WebSockets (e.g., chat apps, live updates)

4. Limitations of Node.js
   i) Not Ideal for CPU-Intensive Tasks
   Since it’s single-threaded: Heavy computations block the event loop
   Example: Image processing Large data calculations
   Solution: Worker threads / microservices
   ii) Callback Hell (historically)
   Deep nested callbacks can make code messy (Though modern solutions exist: Promises, async/await)
   iii) Less Mature for Heavy Enterprise Workloads
   Some areas (like heavy multi-threading or complex transactions) are better handled by languages like Java
   iv) Error Handling Complexity
   Asynchronous code can make debugging harder if not structured properly
   v) API Instability in Some Packages
   Open-source ecosystem is huge, but: Some libraries are poorly maintained

5. V8 Engine
   The Google Chrome V8 Engine (commonly called V8) is a high-performance JavaScript engine developed by Google.
   Its main job: Convert JavaScript code into machine code so the computer can execute it fast.
   How V8 Works (Step-by-Step)
   i) Parsing
   Reads JavaScript code
   Converts it into an Abstract Syntax Tree (AST)
   👉 Think: breaking code into a structured format
   ii) Ignition (Interpreter)
   V8 first uses Ignition (its interpreter)
   Converts AST → Bytecode
   Executes the code quickly without waiting for full optimization
   👉 Fast startup time
   iii) TurboFan (Compiler)
   Frequently used code (“hot code”) is optimized by TurboFan
   Converts bytecode → optimized machine code
   👉 This is called Just-In-Time (JIT) Compilation
   iii) Execution
   Machine code runs directly on CPU
   Optimized paths make execution very fast
   iv) De-optimization
   If assumptions fail (e.g., variable types change), V8:
   Falls back to unoptimized code
   Re-optimizes again if needed
   👉 Smart but dynamic optimization

6. Key Concepts
   i) Just-In-Time (JIT) Compilation
   Combines: Interpreter (fast start) and Compiler (high performance)
   ii) Hidden Classes
   V8 internally optimizes objects using hidden classes
   Objects with same structure → faster access
   iii) Inline Caching
   Caches object property access
   Avoids repeated lookups → faster execution
   iv) Garbage Collection
   Automatically frees memory
   Uses Generational Garbage Collection: Young Generation (short-lived objects) Old Generation (long-lived objects)
   v) Call Stack & Heap
   Call Stack → function execution
   Heap → memory allocation for objects
   vi) Why V8 is Fast
   Compiles JS to native machine code
   Uses JIT optimization
   Smart memory management
   Optimizes frequently used code paths

7. nodemon module
   nodemon is a utility that helps develop Node.js applications by automatically restarting the node application when file changes in the directory are detected. It is particularly useful for development, where you might frequently change your code and need the server to reflect those changes without manually restarting it each time.
   You can install nodemon globally or as a development dependency

   npm install --save-dev nodemon
   npm install -g nodemon
   

   After installing, you can run your application using nodemon instead of node

   nodemon your_script.js
   

https://www.youtube.com/watch?v=ooBxSg1Cl1w