• What is Node.js?

    • Node.js is a JavaScript runtime environment that runs JavaScript code outside the browser.
    • Built on Chrome’s V8 engine for fast execution.
    • Allows building server-side and backend applications using JavaScript.
    • Supports non-blocking, event-driven architecture for handling multiple requests efficiently.
    • Comes with npm (Node Package Manager) to manage packages and dependencies.

    Tip: Node.js lets you use JavaScript for both frontend and backend development.

  • Why Node is single-threaded?

    • Node.js uses a single-threaded event loop to handle requests.
    • It is designed to be non-blocking and asynchronous, so one thread can manage many connections efficiently.
    • Heavy I/O operations don’t block the thread; they use callbacks, promises, or async/await.
    • Single-threaded design reduces context switching and memory overhead.

    Tip: Node’s single-threaded model is ideal for I/O-heavy applications, not CPU-intensive tasks.

  • Event loop in Node

    • The event loop is Node.js’s mechanism to handle asynchronous operations.
    • It allows Node to perform non-blocking I/O using a single thread.
    • Works in phases: timers, I/O callbacks, idle/prepare, poll, check, close callbacks.
    • Executes callbacks from callbacks queue when the main thread is free.
    • Enables Node to handle thousands of concurrent connections efficiently.

    Tip: Understanding the event loop is key to writing efficient asynchronous Node.js applications.

  • Non-blocking I/O

    • Non-blocking I/O allows Node.js to initiate I/O operations (like reading files or network requests) without waiting for them to complete.
    • Other code continues executing while I/O is processed asynchronously.
    • Uses callbacks, promises, or async/await to handle results once ready.
    • Improves performance by handling multiple requests concurrently on a single thread.

    Tip: Non-blocking I/O is what makes Node.js fast and scalable for I/O-heavy applications.

  • What is npm?

    • npm (Node Package Manager) is the default package manager for Node.js.
    • Used to install, manage, and share JavaScript packages and libraries.
    • Allows version control of dependencies via package.json.
    • Provides a vast ecosystem of open-source modules.
    • Supports scripts for running tasks like build, test, or start.

    Tip: npm simplifies dependency management and accelerates development with reusable packages.

  • package.json

    • package.json is a manifest file for a Node.js project.
    • Stores project metadata: name, version, description, author, license.
    • Lists dependencies and devDependencies needed for the project.
    • Defines scripts like start, build, test to automate tasks.
    • Helps npm install, update, and manage packages consistently.

    Tip: Always keep package.json updated to ensure project reproducibility and dependency management.

  • What is module in Node?

    • A module in Node.js is a reusable block of code encapsulated in a file.
    • Provides functionality that can be exported and imported using module.exports or exports.
    • Can be built-in (core), third-party (npm), or custom modules.
    • Helps organize code into smaller, maintainable pieces.

    Tip: Modules make Node.js applications modular, reusable, and easier to maintain.

  • CommonJS

    • CommonJS is a module system used in Node.js.
    • Uses require() to import modules and module.exports to export them.
    • Synchronous loading of modules, suitable for server-side environments.
    • Enables modular and reusable code structure.
    • Standard for most Node.js core and npm packages.

    Tip: CommonJS is the default module system in Node.js, though ES Modules (import/export) are also supported.

  • What is require?

    • require() is a Node.js function used to import modules into a file.
    • Loads core, third-party, or custom modules.
    • Returns the module.exports object from the required module.
    • Synchronous operation: code waits until the module is loaded.
    • Example:
    const fs = require('fs'); // import Node.js file system module

    Tip: Use require() to organize code by reusing modules efficiently in Node.js.

  • What is fs module?

    • fs (File System) is a built-in Node.js module for working with files and directories.
    • Allows reading, writing, updating, deleting, and watching files.
    • Supports synchronous and asynchronous methods.
    • Examples of methods: fs.readFile(), fs.writeFile(), fs.appendFile(), fs.unlink().

    Tip: Use asynchronous methods in fs to avoid blocking the Node.js event loop.

  • What is path module?

    • path is a built-in Node.js module for working with file and directory paths.
    • Provides utilities to join, resolve, normalize, and parse paths across different OS.
    • Common methods: path.join(), path.resolve(), path.basename(), path.extname().
    • Helps avoid errors with file separators (/ vs \\) across platforms.

    Tip: Use path to handle file paths safely and consistently in Node.js projects.

  • What is http module?

    • http is a built-in Node.js module used to create HTTP servers and clients.
    • Allows handling requests and sending responses over the web.
    • Common methods: http.createServer(), server.listen(), req.on(), res.write(), res.end().
    • Forms the foundation for building web servers without additional frameworks.

    Tip: Use http for lightweight servers; for complex apps, combine with frameworks like Express.js.

  • How Node handles async tasks

  • What is process?

  • What is env variable?

  • What is cluster?

  • What is child process?

  • What is buffer?

  • What is stream?

  • Readable vs writable stream