q: What is Node.js? Where can you use it?
ans:
- Node.js is an open-source, cross-platform JavaScript runtime environment and library.
- It is used for creating server-side web applications.
- Node.js can be used for developing real-time web applications, network applications, general-purpose applications, and distributed systems.

q: Why use Node.js?
ans:
- Node.js is generally fast and rarely blocks.
- It offers a unified programming language and data type, as everything is asynchronous.
- It yields great concurrency, making it suitable for handling multiple requests simultaneously.

q: How does Node.js work?
ans:
- Clients send requests to the web server.
- Node.js retrieves incoming requests and adds them to the Event Queue.
- The Event Loop processes simple requests and passes them to the corresponding clients.
- Complex requests are assigned to a single thread from the Thread Pool.
- Once the task is completed, the response is sent back to the client.

q: Why is Node.js Single-threaded?
ans:
- Node.js is single-threaded for async processing, which improves performance and scalability under typical web loads.

q: If Node.js is single-threaded, then how does it handle concurrency?
ans:
- Node.js follows the Single-Threaded Event Loop Model.
- It manages concurrency through the event loop, which processes multiple client requests asynchronously.

q: Explain callback in Node.js.
ans:
- A callback function is called after a given task, allowing other code to run in the meantime.
- Node.js heavily relies on callbacks for asynchronous operations.

q: What are the advantages of using promises instead of callbacks?
ans:
- Promises offer a more structured control flow for asynchronous logic.
- They have low coupling, built-in error handling, and improved readability compared to callbacks.

q: How would you define the term I/O?
ans:
- I/O refers to transferring data to or from a medium, such as physical devices, networks, or files within a system.

q: How is Node.js most frequently used?
ans:
- Node.js is widely used for real-time chats, Internet of Things, single-page applications, streaming applications, real-time collaboration tools, and microservices architecture.

q: What is NPM?
ans:
- NPM stands for Node Package Manager, responsible for managing packages and modules for Node.js.
- It provides online repositories for Node.js packages/modules and a command-line utility for package management.

q: What are the modules in Node.js?
ans:
- Core Modules like HTTP, util, fs, url, query string, stream, and zlib provide basic functionality for web applications.
- Additional modules can be included using the require() function.

q: What is the purpose of the module .Exports?
ans:
- .Exports is used to encapsulate code into a single unit that can be imported into another file using the require() function.

q: Why is Node.js preferred over other backend technologies like Java and PHP?
ans:
- Node.js is preferred for its speed, extensive package ecosystem (NPM), suitability for real-time applications, synchronization of code between server and client, and ease of use for JavaScript developers.

q: What is the difference between Angular and Node.js?
ans:
- Angular is a frontend development framework written in TypeScript for building single-page applications.
- Node.js is a server-side environment written in C++ for building fast and scalable networking applications.

q: Which database is more popularly used with Node.js?
ans:
- MongoDB is the most commonly used database with Node.js due to its NoSQL, document-oriented nature, high performance, availability, and scalability.

q: What are some of the most commonly used libraries in Node.js?
ans:
- ExpressJS: A flexible web application framework.
- Mongoose: A framework for connecting applications to databases.

q: What are the pros and cons of Node.js?
ans:
Pros:
- Fast processing and event-based model.
- Extensive package ecosystem (NPM).
- Suitable for streaming data and I/O intensive operations.

Cons:
- Not suitable for heavy computational tasks.
- Complex callback handling.
- Limited support for relational databases.

q: What is the command used to import external libraries?
ans:
- The "require" command is used to import external libraries/modules in Node.js.

q: What does event-driven programming mean?
ans:
- Event-driven programming uses events to trigger functions, allowing asynchronous execution of tasks based on user actions or system events.

q: What is an Event Loop in Node.js?
ans:
- The Event Loop is a mechanism that handles asynchronous callbacks in Node.js, ensuring non-blocking I/O operations.

q: Differentiate between process.nextTick() and setImmediate()?
ans:
- process.nextTick() postpones the execution of a callback until the next pass around the event loop or after the current execution.
- setImmediate() executes a callback on the next cycle of the event loop, returning control to the event loop for I/O operations.

q: What is an EventEmitter in Node.js?
ans:
- EventEmitter is a class that holds objects capable of emitting events.
- When an event occurs, all attached functions are called synchronously.

q: What are the two types of API functions in Node.js?
ans:
- Asynchronous, non-blocking functions.
- Synchronous, blocking functions.

q: What is the package.json file?
ans:
- The package.json file contains metadata for a Node.js project, including dependencies, scripts, and other project-specific information.

q: How would you use a URL module in Node.js?
ans:
- The URL module provides utilities for URL resolution and parsing in Node.js, making web address manipulation easier.

q: What is the Express.js package?
ans:
- Express.js is a flexible web application framework for Node.js, providing features to develop both web and mobile applications.

q: How do you create a simple Express.js application?
ans:
- Create route handlers using request and response objects.
- Set up routes using the Express Router.
- Define middleware functions for various tasks.

q: What are streams in Node.js?
ans:
- Streams are objects used for continuous reading or writing of data.
- There are four types: Readable, Writable, Duplex, and Transform.

q: What is piping in Node.js?
ans:
- Piping is a mechanism to connect the output of one stream to the input of another stream, facilitating data transfer between streams.

q: What are some of the flags used in the read/write operations in files?
ans:
- Flags like 'r', 'w', 'a', 'r+', 'w+', 'a+', etc., are used in file read/write operations to specify the file's opening mode.

q: How do you open a file in Node.js?
ans:
- Use the fs module's fs.open() method to open a file in Node.js, specifying the file path and opening mode.

q: What is callback hell?
ans:
- Callback hell, or the pyramid of doom, refers to intensively nested, unreadable, and unmanageable callbacks in asynchronous code, making it hard to read and debug.

q: What is a reactor pattern in Node.js?
ans:
- The reactor pattern is a concept of non-blocking I/O operations, providing a handler for each I/O operation and utilizing a demultiplexer to manage I/O requests.

q: Describe Node.js exit codes.
ans:
- Node.js exit codes indicate the termination status of a process, with 0 indicating success and non-zero values indicating errors or specific exit reasons.

q: Explain the concept of

 middleware in Node.js.
ans:
- Middleware functions in Node.js receive the request and response objects, allowing code execution, request/response modification, and passing control to the next middleware in the stack.

q: What are the different types of HTTP requests?
ans:
- HTTP requests include GET, POST, HEAD, and DELETE, each used for specific actions like retrieving data, making changes, or deleting resources.

q: How would you connect a MongoDB database to Node.js?
ans:
- Use the MongoDB Node.js driver or an ODM like Mongoose to connect a Node.js application to a MongoDB database, specifying the connection URL and database name.


50. How would you connect a MongoDB database to Node.js?
   - Install the MongoDB Node.js driver using npm.
   - Use the MongoClient to connect to the MongoDB database.

51. What is the purpose of NODE_ENV?
   - NODE_ENV is an environment variable used to determine the current environment in which the Node.js application is running, such as development, staging, or production.

52. List the various Node.js timing features.
   - setTimeout
   - setInterval
   - setImmediate
   - process.nextTick

53. What is WASI, and why is it being introduced?
   - WASI (WebAssembly System Interface) is a modular system interface for WebAssembly, providing a portable way to run WebAssembly modules outside of the browser.
   - It is being introduced to provide a standardized interface for running WebAssembly code in different environments, such as server-side applications.

54. What is a first-class function in JavaScript?
   - In JavaScript, functions are treated as first-class citizens, meaning they can be assigned to variables, passed as arguments to other functions, and returned from functions.

55. How do you manage packages in your Node.js project?
   - Use npm (Node Package Manager) to install, uninstall, and manage dependencies in a Node.js project.
   - Define dependencies in the package.json file.

56. How is Node.js better than other frameworks?
   - Node.js is built on the V8 JavaScript engine, making it fast and efficient.
   - It uses non-blocking I/O operations, making it suitable for handling concurrent requests.
   - It allows for the use of JavaScript on both the client and server-side.

57. What is a fork in Node.js?
   - The fork method in Node.js creates a new child process that runs a separate Node.js instance, allowing for parallel execution of tasks.

58. List down the two arguments that async.queue takes as input.
   - A worker function
   - An optional concurrency limit

59. What is the purpose of module.exports?
   - module.exports is used to export functions, objects, or values from a module, allowing them to be accessed by other modules using the require() function.

60. What tools can be used to assure consistent code style?
   - ESLint
   - Prettier
   - Jest

61. What is the difference between JavaScript and Node.js?
   - JavaScript is a programming language that runs in web browsers and other environments, while Node.js is a runtime environment for executing JavaScript code outside of a web browser.

62. What is the difference between asynchronous and synchronous functions?
   - Synchronous functions block the execution of other code until they are complete, while asynchronous functions allow other code to continue executing while they are running.

63. What are the asynchronous tasks that should occur in an event loop?
   - I/O operations
   - Timers
   - Callback functions

64. What is the order of execution in control flow statements?
   - Control flow statements are executed in the order in which they are encountered in the code.

65. What are the input arguments for an asynchronous queue?
   - A worker function
   - An optional concurrency limit

66. Are there any disadvantages to using Node.js?
   - Not suitable for CPU-intensive tasks
   - Can consume a lot of memory for large numbers of connections

67. What is the primary reason for using the event-based model in Node.js?
   - Performance, as it allows for non-blocking I/O operations

68. What is the difference between Node.js and Ajax?
   - Ajax is a client-side technology used for asynchronous communication between the client and server, while Node.js is a server-side runtime environment.

69. What is the advantage of using Node.js?
   - Fast and scalable
   - Well-suited for real-time applications
   - Can handle a large number of connections

70. Does Node run on Windows?
   - Yes, Node.js runs on Windows.

71. Can you access DOM in Node?
   - No, Node.js does not have access to the Document Object Model (DOM) since it runs outside of a browser environment.

72. Why is Node.js quickly gaining attention from JAVA programmers?
   - Due to its speed, scalability, and efficiency compared to Java for server-side development.

73. What are the challenges with Node.js?
   - Single-threaded nature
   - Relatively new compared to other technologies
   - Memory consumption for large numbers of connections

74. What is "non-blocking" in Node.js?
   - Non-blocking refers to the ability of Node.js to handle multiple tasks simultaneously without waiting for the completion of one task before starting the next.

75. How does Node.js overcome the problem of blocking I/O operations?
   - By using an event-driven, non-blocking I/O model

76. How can we use async await in Node.js?
   - Use the async keyword to mark a function as asynchronous and the await keyword to wait for a promise to resolve.

77. Why should you separate the Express app and server?
   - Easier testing and scalability
   - Simplifies switching to a different server

78. Explain the concept of a stub in Node.js.
   - A stub is a simplified version of a function used in unit testing to replace a real function.

79. What is the framework that is used majorly in Node.js today?
   - Express

80. What are the security implementations present in Node.js?
   - Restricted code execution environment
   - TLS/SSL encryption

81. What is Libuv?
   - Libuv is a library used by Node.js for asynchronous I/O operations.

82. What are global objects in Node.js?
   - Objects available in all modules without requiring an explicit require statement

83. Why is assert used in Node.js?
   - For writing effective tests

84. Why is ExpressJS used?
   - For building web applications in Node.js due to its simplicity and flexibility

85. What is the use of the connect module in Node.js?
   - Handles middleware in web applications

86. What's the difference between 'front-end' and 'back-end' development?
   - Front-end focuses on the client side, while back-end focuses on the server side of applications.

87. What are LTS releases of Node.js?
   - Long-term support releases, recommended for production use

88. What do you understand about ESLint?
   - A tool used to analyze and flag errors in JavaScript code

89. Define the concept of the test pyramid.
   - Illustrates the distribution of different types of tests, with unit tests forming the base and end-to-end tests at the top.

90. How does Node.js handle child threads?
   - By creating separate instances of the Node.js runtime environment

91. What is an Event Emitter in Node.js?
   - A module that facilitates communication between objects in a Node.js application.

92. How to Enhance Node.js Performance through Clustering?
   - By utilizing multiple CPU cores with the cluster module

93. What is a thread pool, and which library handles it in Node.js?
   - A collection of threads for executing tasks in parallel, handled by the libuv library.

94. How are worker threads different from clusters?
   - Worker threads create multiple threads within a single process, while clusters create multiple instances of a Node.js process.

95. How to measure the duration of async operations?
   - Using console.time and console.timeEnd methods

 or performance.now method.

96. How to measure the performance of async operations?
   - Using built-in flags, tools like perf, or third-party libraries like benchmark.js.

97. What are the types of streams available in Node.js?
   - Readable, writable, duplex, and transform streams.

98. What is meant by tracing in Node.js?
   - Profiling the performance of an application by recording function calls and events.

99. Where is package.json used in Node.js?
   - In the root directory of a Node.js application, used by npm to manage dependencies.

100. What is the difference between readFile and createReadStream in Node.js?
   - readFile is better for small files, while createReadStream is better for large files.

101. What is the use of the crypto module in Node.js?
   - Provides cryptographic functionality such as generating secure random numbers and encryption.

102. What is a passport in Node.js?
   - Authentication middleware for Node.js.

103. How to get information about a file in Node.js?
   - Using fs.stat method.

104. How does the DNS lookup function work in Node.js?
   - Using the DNS module to perform DNS lookups.

105. What is the difference between setImmediate() and setTimeout()?
   - setImmediate() has a higher priority than setTimeout().

106. Explain the concept of Punycode in Node.js.
   - A character encoding scheme used to represent Unicode characters with ASCII characters in domain names.

107. Does Node.js provide any Debugger?
   - Yes, Node.js provides a built-in debugger.

108. Is cryptography supported in Node.js?
   - Yes, through the crypto module.

109. Why do you think you are the right fit for this Node.js role?
   - Experience building scalable server-side applications with Node.js.
   - Strong teamwork and communication skills.