Node.js Mastery: Challenging Interview Questions for 2025 Quiz

Sharpen your Node.js expertise with this quiz designed for 2025, covering essential concepts, asynchronous programming, event loops, modules, and practical coding scenarios. Enhance your readiness for interviews with focused questions on the fundamentals and advanced features of Node.js.

1. Node.js Event Loop Basics

   Which component in Node.js processes asynchronous callbacks and manages non-blocking I/O operations?

   1. Callback Heap
   2. Request Queue
   3. Event Loop
   4. Main Thread

   Explanation: The event loop is responsible for processing asynchronous callbacks and managing non-blocking I/O in Node.js. The main thread only initiates actions but doesn't handle ongoing asynchronous events. The request queue and callback heap are not actual components in Node.js, making them incorrect choices.

2. Default Port for HTTP Server

   What is the default port commonly used by an HTTP server created using Node.js’s built-in module?

   1. 443
   2. 8080
   3. 80
   4. 3000

   Explanation: Port 80 is the default port for HTTP servers, making it the standard unless otherwise specified. Ports 3000 and 8080 are popular choices for development but are not defaults. Port 443 is reserved for HTTPS, not HTTP.

3. Type of Node.js Module System

   Which module system is used by default in Node.js when requiring modules with the 'require' function?

   1. AMD
   2. ES Modules
   3. UMD
   4. CommonJS

   Explanation: Node.js uses the CommonJS module system by default with the 'require' function, enabling server-side JavaScript modularity. ES Modules are supported in modern versions but are not the default when using 'require'. AMD and UMD are formats used mostly for client-side JavaScript and are not natively supported in Node.js.

4. Node.js Global Objects

   Which global object in Node.js provides information about and control over the current process?

   1. os
   2. Buffer
   3. process
   4. global

   Explanation: The process object in Node.js allows access to details of the running process, such as environment variables and exiting the process. Global refers to the global scope but does not provide process-specific information. Buffer is used for binary data manipulation, and os provides operating system-related utility functions.

5. Asynchronous Programming Example

   In Node.js, which method is often used to execute a function after a specified delay in milliseconds?

   1. delayFunction
   2. afterDelay
   3. waitFor
   4. setTimeout

   Explanation: setTimeout is the correct method for delaying function execution by a specified number of milliseconds in Node.js. afterDelay, waitFor, and delayFunction are not valid global methods in Node.js, nor do they perform this function.

6. Understanding Streams

   Which stream type in Node.js allows for data to be written but not read?

   1. Writable
   2. Readable
   3. Transform
   4. Duplex

   Explanation: Writable streams support writing data but do not allow reading from them, making them the correct answer. Readable streams do the opposite, duplex streams can both read and write, and transform streams are a specific type of duplex stream capable of modifying data.

7. Handling Uncaught Exceptions

   Which event can be used to catch unhandled exceptions in Node.js and prevent the process from crashing abruptly?

   1. processError
   2. uncaughtException
   3. errorCatch
   4. exceptionThrown

   Explanation: The 'uncaughtException' event allows listening for exceptions not handled elsewhere, helping to log errors before process termination. errorCatch, exceptionThrown, and processError are not recognized events and will not serve this purpose.

8. Checking for Array Buffer

   If you want to check whether an object is a Buffer in Node.js, which method would you use?

   1. Array.isBuffer
   2. Buffer.isBuffer
   3. Buffer.check
   4. Buffer.test

   Explanation: The method Buffer.isBuffer(object) correctly determines if the given object is a Buffer instance. Buffer.check and Buffer.test are not valid buffer methods, and Array.isBuffer only checks for arrays, not buffers.

9. Reading a File Asynchronously

   Which built-in module provides an asynchronous method to read the contents of a text file in Node.js?

   1. fs
   2. net
   3. http
   4. path

   Explanation: The fs module supplies functions for file system operations, including asynchronous file reading. The net module is for networking, http is for HTTP servers and clients, and path helps manipulate file paths, but none of these read files directly.

10. Node.js Package Initialization

    What command is used to create a new package.json file with default values in a Node.js project directory?

    1. npm create
    2. npm init -y
    3. npm start
    4. npm install

    Explanation: npm init -y initializes a package.json file using default values quickly, which is essential for package management in Node.js. npm start is used to run scripts, npm create doesn't exist, and npm install is for installing packages, not initializing package.json.