Node Interview Questions For Freshers
What is the purpose of 'module.exports' in Node.js?
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The purpose of 'module.exports' in Node.js is to define the functionality or data that can be exported from a module and used in other parts of the application. It allows developers to encapsulate and share code between different files, making it easier to organize and maintain the application.
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What are the differences between Express.js and Node.js?
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Explain the concept of middleware in Express.js
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What is a promise in Node.js?
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A promise in Node.js is an object used to handle asynchronous operations. It represents the eventual completion or failure of an asynchronous operation and allows us to write cleaner and more maintainable code by avoiding excessive use of callbacks. It provides a better way to handle and chain multiple asynchronous operations together.
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What is the purpose of 'fs' module in Node.js?
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How can you read and write files in Node.js?
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What is the event loop in Node.js?
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Explain the role of 'buffer' class in Node.js
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What is the purpose of 'path' module in Node.js?
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The 'path' module in Node.js provides utility functions for working with file and directory paths. Its purpose is to handle path-related operations, such as joining path segments, resolving paths, extracting file extensions, and more. It simplifies the process of working with file paths in a cross-platform manner.
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How can you handle errors in Node.js?
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What is the significance of '__dirname' in Node.js?
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How do you handle asynchronous operations in Node.js?
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Explain the difference between process.nextTick() and setImmediate() in Node.js
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`process.nextTick()` and `setImmediate()` are both methods used in Node.js for scheduling asynchronous operations. The difference is that `process.nextTick()` schedules a callback to be executed on the next loop iteration, before I/O operations, while `setImmediate()` schedules a callback to be executed on the next cycle of the event loop after I/O operations have been completed.
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What are streams in Node.js?
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Streams are an important concept in Node.js that facilitate the efficient handling of data. They enable the processing of data in chunks, rather than loading the entire dataset into memory. This is especially useful when dealing with large files or network communication, as it improves performance and reduces memory consumption.
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What is the purpose of EventEmitter in Node.js?
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The purpose of EventEmitter in Node.js is to allow communication between different components or modules in an event-driven architecture. It provides a set of methods to emit and listen to events, enabling asynchronous and decoupled communication between different parts of a Node.js application.
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What is an event in Node.js?
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In Node.js, an event is a signal that indicates that a specific action or condition has occurred. Events are emitted by objects (known as EventEmitters) and can be listened to or handled by event listeners to execute specific code when the event is triggered.
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What is callback function in Node.js?
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In Node.js, a callback function is a function that is passed as an argument to another function and is executed after the completion of some asynchronous operation. It allows for non-blocking operations, ensuring that the program does not wait for a response before executing the next line of code.
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Explain the use of 'require' in Node.js
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In Node.js, the 'require' function is used to include and use external modules or libraries in a Node.js application. It acts as an import statement, allowing developers to use pre-existing functionality from other files or modules within their own application.
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What is the purpose of package.json file?
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What is NPM?
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How do you install Node.js?
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To install Node.js, you can visit the official Node.js website and download the appropriate installer for your operating system. Run the installer and follow the on-screen instructions to complete the installation process. Once installed, you can verify the installation by typing "node -v" in your command prompt or terminal.
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How can you perform unit testing in Node.js?
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What is the purpose of 'util' module in Node.js?
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The 'util' module in Node.js provides utility functions that are commonly used in programming. It includes various functions for debugging, error handling, object manipulation, and asynchronous operations. The purpose of this module is to simplify and enhance the development process in Node.js by offering a set of helpful tools.
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What is a Node.js?
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Node.js is a runtime environment that allows developers to execute JavaScript code outside of a web browser. It uses an event-driven, non-blocking I/O model, making it efficient for building scalable and real-time applications. It is particularly popular for building server-side applications and APIs.
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What is the purpose of 'child_process' module in Node.js?
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Explain the role of 'crypto' module in Node.js
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What is the purpose of 'net' module in Node.js?
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What is event-driven programming in Node.js?
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How can you create a basic HTTP server in Node.js?
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What is the use of 'URL' module in Node.js?
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Explain the role of 'querystring' module in Node.js
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What is the purpose of 'cluster' module in Node.js?
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What is the 'process' object in Node.js?
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Node Intermediate Interview Questions
What is the use of 'child_process' module in Node.js?
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The 'child_process' module in Node.js allows for the creation and management of child processes. This is useful for running external applications, executing system commands, and performing tasks concurrently. It also provides methods for communication between the parent and child processes.
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What is the use of 'fs' module in Node.js?
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The 'fs' module in Node.js is used to access and interact with the file system. It provides functions for reading, writing, updating, and deleting files and directories on the server or local machine. It is a core module in Node.js and is commonly used for handling file operations in web applications and server-side scripting.
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Explain the role of 'dns' module in Node.js
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The 'dns' module in Node.js provides functions to perform DNS (Domain Name System) lookups and reverse lookups. It allows applications to resolve domain names into IP addresses and vice versa, as well as perform other DNS operations like retrieving MX (Mail Exchange) records and checking if a domain is valid.
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What is the purpose of 'worker_threads' module in Node.js?
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The purpose of the 'worker_threads' module in Node.js is to enable the creation and management of multithreaded worker threads. This allows developers to leverage the power of multiple threads for performing parallel and CPU-intensive tasks, improving the overall performance and responsiveness of Node.js applications.
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How can you handle errors in asynchronous functions in Node.js?
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In Node.js, you can handle errors in asynchronous functions by using try-catch blocks. Any error thrown inside the async function can be caught using try-catch. Additionally, you can also use promises and the "catch" method to handle errors in async functions. Error handling can include logging the error, returning an error message, or performing any necessary error recovery actions.
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What is the use of 'tty' module in Node.js?
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The 'tty' module in Node.js provides a way to interact with the terminal device. It enables reading input from and writing output to the terminal, as well as controlling terminal settings and behavior. This module is particularly useful for creating interactive command-line applications and tools in Node.js.
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What is the purpose of 'punycode' module in Node.js?
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The 'punycode' module in Node.js is used for converting non-ASCII domain names to ASCII-compatible encoding (ACE) and vice versa. It provides a way to represent non-ASCII characters in a domain name using only ASCII characters, allowing for internationalized domain names (IDNs) to be used in systems that only support ASCII.
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What is the difference between EventEmitter and Streams in Node.js?
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EventEmitter and Streams are both modules in Node.js, but they serve different purposes. EventEmitter is used for asynchronous event-driven programming, allowing objects to emit and listen for events. Streams, on the other hand, are used for handling continuous flows of data, enabling efficient processing of large amounts of data in a memory-friendly manner.
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What is the purpose of 'argv' in process object?
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The 'argv' property in the process object is an array that contains the command line arguments passed to the Node.js process. It allows developers to access and manipulate the arguments passed to a Node.js application during runtime.
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How can you test APIs in Node.js?
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In Node.js, you can test APIs by using various testing frameworks like Mocha, Chai, and Supertest. These frameworks allow you to write test cases that send HTTP requests to your API endpoints and validate the responses to ensure they meet the expected results.
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What is the purpose of 'assert' module in Node.js?
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The 'assert' module in Node.js is used for assertion testing. It provides functions that can be used to write assertions in our code in order to check if certain conditions are met during the execution of a program. It helps in debugging and finding errors in our code by verifying the expected behavior.
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Explain the role of 'util' module in Node.js
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The 'util' module in Node.js provides several utility functions that are commonly used in the development of Node.js applications. It includes functions for debugging, formatting and manipulating objects, working with error handling and routines for creating custom event emitters.
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What is the purpose of 'querystring' module in Node.js?
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The purpose of the 'querystring' module in Node.js is to parse and stringify URL query strings. It provides methods to extract and manipulate query parameters, making it easier to work with data transferred in the URL's query string format.
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How can you handle file system events in Node.js?
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In Node.js, file system events can be handled using the built-in 'fs' module. Specifically, the 'watch' and 'watchFile' methods can be used to monitor changes to files and directories. These methods provide event listeners that can be used to execute custom code when certain file system events occur, such as file creation, modification, or deletion.
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What is the difference between setTimeout and setImmediate in Node.js?
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In Node.js, `setTimeout` and `setImmediate` are both used for asynchronous execution. `setTimeout` schedules a callback function to run after a specific delay, while `setImmediate` schedules a callback function to run right after the I/O events in the current event loop iteration.
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Explain the role of 'stream' module in Node.js
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The 'stream' module in Node.js is a powerful feature that allows for efficient handling of data that can be read or written sequentially. It provides a way to read or write data in chunks, rather than loading all the data into memory at once. This is particularly useful when dealing with large amounts of data or when working with data from external sources or network streams.
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What is the purpose of 'https' module in Node.js?
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The 'https' module in Node.js is used for creating a secure HTTPS server or making secure HTTP requests. It provides methods for handling SSL/TLS certificates, server-side encryption, and implementing secure communication between a client and server using the HTTPS protocol.
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How can you handle cookies in Node.js?
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To handle cookies in Node.js, you can use the `cookie-parser` middleware. This middleware allows you to parse and set cookies in your application. It enables you to read and write cookies using the `req.cookies` object and set cookies using the `res.cookie()` method.
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What is the use of 'cluster' module in Node.js?
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The 'cluster' module in Node.js allows for the creation of child processes (worker processes) to handle incoming HTTP requests, thus enabling the utilization of multiple CPU cores in a single Node.js application. This helps in improving the overall performance and scalability of the application.
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Explain the role of 'zlib' module in Node.js
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The 'zlib' module in Node.js is used for compression and decompression of data streams. It provides functions to compress and decompress data using the zlib compression algorithm. This module is commonly used in applications that require efficient compression and decompression of data, such as file compression and network protocols.
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What is the purpose of 'os' module in Node.js?
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The 'os' module in Node.js provides a set of operating system-related utility methods and properties. It allows developers to access information about the current operating system, such as CPU architecture, available memory, network interfaces, and more. It is useful for building cross-platform applications that require system-level information and interaction.
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How can you handle file upload in Node.js?
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In Node.js, you can handle file upload using the "multer" middleware. Multer provides easy handling of multipart/form-data, allowing you to receive files on the server side. It offers various configurations and options for handling file uploads, such as specifying file size limits and file destination.
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What are the benefits of using Express.js?
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Express.js is a popular framework for Node.js that offers several benefits. It provides a minimalist approach, making it lightweight and efficient for building web applications. Express.js also offers a robust set of features, such as routing, middleware support, and easy integration with databases. It allows for quick development and scalability while providing flexibility for customizations.
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Explain the usage of 'process.argv' in Node.js
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The 'process.argv' is an array that stores the command line arguments passed to a Node.js script. It allows developers to access and manipulate these arguments within their code. The first element in the array is always the path of the Node.js executable, and the second element is the path of the script being executed. Additional elements represent the arguments passed after the script's path.
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What are the different types of streams in Node.js?
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In Node.js, there are four types of streams: Readable, Writable, Duplex, and Transform. Readable streams allow reading data, Writable streams allow writing data, Duplex streams can both read and write data, and Transform streams can modify or transform data as it is being read or written.
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What is the concept of non-blocking I/O in Node.js?
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Non-blocking I/O is a key concept in Node.js that allows the server to handle multiple requests efficiently. Instead of waiting for I/O operations to complete, Node.js delegates them to the operating system and continues executing other tasks. This asynchronous approach helps maximize performance by ensuring that the server is not idle while waiting for I/O operations to finish.
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What is the difference between Node.js and other server-side frameworks?
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Node.js is a platform that allows JavaScript to run on the server-side, unlike other frameworks that use different programming languages such as PHP, Python, or Ruby. Node.js is known for its event-driven architecture, non-blocking I/O operations, and ability to handle a large number of concurrent connections, making it highly efficient and scalable for building real-time applications.
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What is HTTP in Node.js?
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In Node.js, HTTP (Hypertext Transfer Protocol) is a built-in module that allows creating web servers and making HTTP requests. It provides functionality to handle incoming HTTP requests and respond with appropriate HTTP responses, enabling the development of web applications and APIs.
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Node Interview Questions For Experienced
How can you create a server using the 'http' module in Node.js?
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To create a server using the 'http' module in Node.js, you first need to require the module. Then, you can use the 'createServer' method to create a server object. Finally, you can use the server's 'listen' method to specify a port and start the server.
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How does clustering work in Node.js?
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Clustering in Node.js involves creating a cluster of worker processes that can handle incoming requests. The cluster module allows for efficient distribution of incoming connections across multiple processes, improving overall system performance. Each worker in the cluster can handle multiple requests simultaneously, leading to better scalability and resource utilization.
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Explain the role of 'http2' module in Node.js
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The 'http2' module in Node.js is responsible for providing support for the HTTP/2 protocol. It allows Node.js applications to leverage the features and improvements offered by HTTP/2, such as multiplexing and server push, to enhance the performance and efficiency of web applications.
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What is the purpose of 'gulp' module in Node.js?
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The 'gulp' module in Node.js is a task runner that automates repetitive tasks such as minifying and concatenating files, optimizing images, and running tests. It helps improve development workflow by streamlining these tasks and allowing developers to define and run them in a simple and efficient manner.
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Explain the role of 'mocha' module in Node.js
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The 'mocha' module is a popular testing framework for Node.js. It provides a simple and flexible way to write and execute tests. Mocha allows developers to easily define test suites, write test cases, and generate reports. It also supports asynchronous testing and provides various assertion styles to verify expected outcomes.
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What is the use of 'deasync' module in Node.js?
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What is the purpose of 'throw' statement in Node.js?
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The purpose of the 'throw' statement in Node.js is to generate a custom error in the code. It allows the developer to intentionally raise an exception, providing a way to handle exceptional conditions and control the flow of the program.
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How can you perform load testing in Node.js?
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To perform load testing in Node.js, you can use various tools such as Artillery, Loadtest, or Apache JMeter. These tools allow you to simulate high loads on your Node.js server by creating multiple concurrent requests and measuring the performance and responsiveness of your application under different load conditions.
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What is the use of 'nodemailer' module in Node.js?
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The 'nodemailer' module in Node.js is used for sending emails. It provides an easy-to-use interface to create and send email messages using various transport methods such as SMTP, sendmail, and Amazon SES. It includes features like attachments, HTML content, and SMTP authentication, making it a powerful tool for handling email functionality in Node.js applications.
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Explain the role of 'vm2' module in Node.js
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What is the purpose of 'dtrace' module in Node.js?
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The 'dtrace' module in Node.js is used for enabling Dynamic Tracing (DTrace) on Node.js applications. DTrace is a powerful diagnostic framework that allows developers to collect real-time performance and debugging information from running programs, helping in troubleshooting and optimizing application performance.
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How can you handle authentication in Node.js?
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In Node.js, you can handle authentication by using packages like Passport.js or by implementing your own middleware. Passport.js provides various authentication strategies (e.g., local, Google, Facebook) and simplifies the authentication process by handling session management and user authentication.
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What is the use of 'zmq' module in Node.js?
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The 'zmq' module in Node.js is used for implementing ZeroMQ, a high-performance messaging library. It enables Node.js applications to communicate efficiently and asynchronously across multiple threads, processes, or machines. It provides various socket types for different communication patterns such as request-reply, publish-subscribe, and more.
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What is the purpose of 'repl' module in Node.js?
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The 'repl' module in Node.js stands for Read-Eval-Print-Loop and it allows the user to interactively run JavaScript code in a console-like environment. It is useful for testing and debugging code snippets, as well as experimenting with Node.js APIs and features.
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How can you create a GraphQL server in Node.js?
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To create a GraphQL server in Node.js, you can use various packages such as Apollo Server, Express, or GraphQL Yoga. You would start by setting up a Node.js application, installing the necessary dependencies, defining your GraphQL schema, and then implementing resolver functions to handle the queries, mutations, and subscriptions.
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What is the use of 'formidable' module in Node.js?
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The 'formidable' module in Node.js is used for handling HTML form data and file uploads. It provides an easy-to-use API for parsing form data, extracting values, and storing file uploads. This module is useful for building web applications that require form processing and file upload functionality.
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Explain the role of 'url' module in Node.js
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The 'url' module in Node.js provides utilities for URL resolution and parsing. It allows developers to manipulate URLs, parse their components, and resolve relative URLs. It provides methods such as url.parse() for parsing a URL string, url.format() to construct a URL string from its components, and url.resolve() to resolve a relative URL against a base URL.
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What is the purpose of 'dgram' module in Node.js?
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The purpose of the 'dgram' module in Node.js is to provide an implementation of UDP (User Datagram Protocol) sockets. This module allows users to create UDP clients and servers, send and receive UDP datagrams, and handle multicast communications in a straightforward manner.
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How can you implement a WebSocket server in Node.js?
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To implement a WebSocket server in Node.js, you can use the 'ws' library. First, install the library using npm. Then, create an instance of WebSocket.Server, which listens for connections on a specified port. Set up event listeners for the 'connection' and 'message' events to handle incoming connections and messages respectively.
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What is the use of 'bcrypt' module in Node.js?
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The 'bcrypt' module in Node.js is used for password hashing. It provides a way to securely store passwords by hashing them with a salt, making it extremely difficult for hackers to decipher the actual passwords. This module helps enhance the security of user authentication systems.
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Explain the role of 'vm' module in Node.js
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The 'vm' module in Node.js stands for "virtual machine" and provides a way to compile and run JavaScript code within a defined context. It allows developers to create and execute code within isolated environments, providing additional security and flexibility. The module includes methods for compiling and running scripts, creating sandboxes, and managing contexts.
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What is the concept of middleware in Koa.js?
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In Koa.js, middleware refers to functions that are executed in between the handling of a request and the returning of the response. It allows for modular and reusable code, providing features such as logging, authentication, error handling, and much more. Middleware functions are arranged in a stack and can be added or removed as needed.
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The concept of middleware in Koa.js:
In Koa.js, middleware is a key concept that helps in the processing of HTTP requests and responses. It acts as a bridge between the server and the application, allowing for the manipulation and handling of different aspects of the request-response cycle.
Middleware functions in Koa.js are functions that take two parameters: a context object (usually named 'ctx') and a next function. The context object contains information about the current request and response, while the next function is used to pass the control to the next middleware in the chain.
- Order of execution: When a request is received, Koa.js executes the middleware functions in the order they are defined. Each middleware has the ability to perform some operations on the request and response and then decide whether to pass control to the next middleware or not. If a middleware does not call the next function, the chain is halted and the response is sent back from that point.
- Examples of middleware: Middleware functions can perform various tasks, such as logging, parsing the request body, handling errors, serving static files, authenticating users, and more. Here are a few examples:
// Logging middleware
app.use(async (ctx, next) => {
console.log(`Request received: ${ctx.method} ${ctx.url}`);
await next();
console.log(`Response sent: ${ctx.response.status}`);
});
// Error handling middleware
app.use(async (ctx, next) => {
try {
await next();
} catch (error) {
ctx.response.status = 500;
ctx.response.body = 'Internal Server Error';
}
});
Koa.js's middleware ecosystem allows developers to easily plug in and combine different middleware functions to create powerful and flexible web applications. It provides a clean and modular approach to handling requests and responses, enabling developers to focus on specific tasks without having to worry about the overall request-response cycle.