- **Beginner Node.js Interview Questions:**
  1. What is a first class function in Javascript?
     - Functions that can be treated like any other variable.
  2. What is Node.js and how it works?
     - A virtual machine using JavaScript, running Chrome’s V8 engine, with an event-driven architecture.
  3. How do you manage packages in your node.js project?
     - Using npm or yarn, along with package.json and package-lock.json for version control.
  4. How is Node.js better than other frameworks most popularly used?
     - Non-blocking I/O, event-based model, runs on Chrome's V8 engine, faster development, abundant libraries.
  5. Explain the steps how “Control Flow” controls the functions calls?
     - Order of execution, data collection, concurrency limitation, calling subsequent steps.
  6. What are some commonly used timing features of Node.js?
     - setTimeout/clearTimeout, setInterval/clearInterval, setImmediate/clearImmediate, process.nextTick.
  7. What are the advantages of using promises instead of callbacks?
     - Better code manageability, avoiding callback hell.
  8. What is fork in node JS?
     - Used to spawn child processes, creating new instances of V8 engine for multiple workers.
  9. Why is Node.js single-threaded?
     - Experiment in async processing, utilizing event-driven model.
  10. How do you create a simple server in Node.js that returns Hello World?
      ```javascript
      var http = require("http");
      http.createServer(function (request, response) {
          response.writeHead(200, {'Content-Type': 'text/plain'});
          response.end('Hello World\n');
      }).listen(3000);
      ```
  11. How many types of API functions are there in Node.js?
      - Asynchronous, non-blocking functions and synchronous, blocking functions.
  12. What is REPL?
      - Read, Eval, Print, Loop; for evaluating code on the go.
  13. List down the two arguments that async.queue takes as input?
      - Task Function and Concurrency Value.
  14. What is the purpose of module.exports?
      - Exposing functions of a module for use elsewhere.
  15. What tools can be used to assure consistent code style?
      - ESLint for maintaining consistent coding style.

- **Intermediate Node.js Interview Questions:**
  16. What do you understand by callback hell?
      - Nested callbacks making code unreadable and unmaintainable.
  17. What is an event-loop in Node JS?
      - Manages asynchronous operations with queues and listeners.
  18. If Node.js is single threaded then how does it handle concurrency?
      - Managed by libuv library with a thread pool.
  19. Differentiate between process.nextTick() and setImmediate()?
      - process.nextTick() adds to the start of the event queue, setImmediate() to the check phase.
  20. How does Node.js overcome the problem of blocking of I/O operations?
      - Handles I/O operations asynchronously through the event loop.
  21. How can we use async await in node.js?
      - Utilizing async-await pattern for asynchronous operations.
  22. What is node.js streams?
      - Instances of EventEmitter for working with streaming data.
  23. What are node.js buffers?
      - Temporary memory for streaming data in fixed-length sequences of bytes.
  24. What is middleware?
      - Intercepts requests before reaching the business logic.
  25. Explain what a Reactor Pattern in Node.js?
      - Pattern for nonblocking I/O operations.
  26. Why should you separate Express app and server?
      - Encapsulates business logic and application logic, improving readability.
  27. For Node.js, why Google uses V8 engine?
      - Most evolved and fastest JavaScript and WebAssembly engine.
  28. Describe the exit codes of Node.js?
      - Indicate reasons behind process termination.
  29. Explain the concept of stub in Node.js?
      - Replaces functions being tested for easier testing.

- **Advanced Node.js Interview Questions:**
  30. What is an Event Emitter in Node.js?
      - EventEmitter is a class in Node.js capable of emitting events, allowing attached functions to be invoked synchronously.
  31. Enhancing Node.js performance through clustering.
      - Clustering enables multiple instances of the event loop to utilize multiple CPU cores, improving performance.
  32. What is a thread pool and which library handles it in Node.js?
      - The thread pool is managed by the libuv library, which provides support for asynchronous I/O operations.
  33. What is WASI and why is it being introduced?
      - WASI (WebAssembly System Interface) provides a way for WebAssembly modules to interact with the underlying operating system, enhancing efficiency and access to system-level features.