Node.js Interview Questions and Answers For Freshers
setTimeout vs setImmediate vs process.nextTick (() => new Promise((resolve) => resolve('promise')))() .then((p) => console.log(p)) setTimeout(() => console.log('timeout'), 0); setImmediate(() => console.log('immediate')); queueMicrotask(() => console.log('microtask')); process.nextTick(() => console.log('nexttick')); What's the output of this code and why?
nexttick promise microtask timeout immediate
Why is Node.js Single-threaded?
Certainly! Here's a more compact summary: Node.js is single-threaded for async processing, which enables it to achieve better performance and scalability compared to traditional thread-based models. By leveraging an event-driven, non-blocking I/O model, Node.js can efficiently handle concurrent requests without the overhead of creating and managing multiple threads. This approach reduces resource consumption, improves scalability, avoids thread synchronization issues, and enhances overall performance by utilizing CPU cycles more efficiently. However, Node.js may not be suitable for CPU-intensive tasks. Overall, Node.js' single-threaded architecture for async processing provides significant benefits in web and network applications.
What are the advantages of using promises instead of callbacks?
Certainly! Here's a more compact version: Advantages of using promises instead of callbacks include: 1. Structured Control Flow: Promises provide a more specified and structured control flow for asynchronous logic, improving code readability and maintainability. 2. Low Coupling: Promises decouple asynchronous operations from their callbacks, promoting loose coupling and modular code design. 3. Built-in Error Handling: Promises come with built-in error handling capabilities, allowing for easy and centralized error management across asynchronous operations. 4. Improved Readability: Promises offer a more intuitive and expressive coding style, allowing for a linear and sequential flow of operations with methods like `.then()` and `.catch()`. By using promises, developers can write more concise and organized asynchronous code, with improved error handling and enhanced readability.
How would you define the term I/O?
The term I/O is used to describe any program, operation, or device that transfers data to or from a medium and to or from another medium Every transfer is an output from one medium and an input into another. The medium can be a physical device, network, or files within a system
If Node.js is single-threaded, then how does it handle concurrency?
Node.js follows a single-threaded event loop model instead of the traditional multi-threaded request/response model. This allows Node.js to efficiently handle concurrent client requests by leveraging the event-based nature of JavaScript and its callback system. The event loop acts as the central component, orchestrating the flow of operations and processing events and callbacks in a sequential manner. By utilizing the event loop and asynchronous operations, Node.js can manage high concurrency without the need for dedicated threads. This event-driven processing model is the key to Node.js' ability to handle a large number of concurrent requests effectively.
Why is Node.js preferred over other backend technologies like Java and PHP?
Some of the reasons why Node.js is preferred include: Node.js is very fast Node Package Manager has over 50,000 bundles available at the developer's disposal Perfect for data-intensive, real-time web applications, as Node.js never waits for an API to return data Better synchronization of code between server and client due to same code base Easy for web developers to start using Node.js in their projects as it is a JavaScript library
The order of execution within the Node.js event loop can be summarized as follows:
1. `process.nextTick()`: The callbacks scheduled using `process.nextTick()` have the highest priority and are executed first. They are processed in the next tick queue immediately after the current operation completes and before the event loop continues to the next phase. 2. Microtask Queue: After processing `process.nextTick()` callbacks, the event loop moves on to the microtask queue. The microtask queue holds microtasks such as promise callbacks scheduled with `.then()` or `.catch()`. These microtasks are processed in the order they were added to the queue. 3. Phases: After processing the microtask queue, the event loop moves on to the remaining phases, such as timers, Pending(I/O callbacks), idle/prepare, poll, check, and close callback phases, in their respective order. These phases handle other types of tasks and events, including timer callbacks, I/O operations, and other callbacks associated with specific operations. It's important to note that the order described here pertains to the internal workings of the event loop and the priorities within it. External factors, such as other asynchronous operations or events occurring outside the event loop, may have their own order of execution that is not affected by the event loop's internal processing order. In summary, the order of execution within the Node.js event loop is `process.nextTick()`, followed by the microtask queue, and then the remaining phases in their respective order.Yes, that is correct. The order of execution within the Node.js event loop can be summarized as follows: 1. `process.nextTick()`: The callbacks scheduled using `process.nextTick()` have the highest priority and are executed first. They are processed in the next tick queue immediately after the current operation completes and before the event loop continues to the next phase. 2. Microtask Queue: After processing `process.nextTick()` callbacks, the event loop moves on to the microtask queue. The microtask queue holds microtasks such as promise callbacks scheduled with `.then()` or `.catch()`. These microtasks are processed in the order they were added to the queue. 3. Phases: After processing the microtask queue, the event loop moves on to the remaining phases, such as timers, I/O
What are the pros and cons of Node.js?
Fast processing and an event-based model Not suitable for heavy computational tasks Uses JavaScript, which is well-known amongst developers Using callback is complex since you end up with several nested callbacks Node Package Manager has over 50,000 packages that provide the functionality to an application Dealing with relational databases is not a good option for Node.js Best suited for streaming huge amounts of data and I/O intensive operations Since Node.js is single-threaded, CPU intensive tasks are not its strong suit
Explain the difference between frontend and backend development?
Frontend refers to the client-side of an application Backend refers to the server-side of an application It is the part of a web application that users can see and interact with It constitutes everything that happens behind the scenes It typically includes everything that attributes to the visual aspects of a web application It generally includes a web server that communicates with a database to serve requests HTML, CSS, JavaScript, AngularJS, and ReactJS are some of the essentials of frontend development Java, PHP, Python, and Node.js are some of the backend development technologies
What is the purpose of the module .Exports?
In Node.js, a module encapsulates all related codes into a single unit of code that can be parsed by moving all relevant functions into a single file. You may export a module with the module and export the function, which lets it be imported into another file with a needed keyword.
Explain callback in Node.js.
In Node.js, callbacks are functions that are called after a specific task or operation completes. They allow other code to run concurrently, preventing blocking and enabling efficient handling of asynchronous operations. Node.js APIs are designed to support callbacks, making it an integral part of the platform's asynchronous nature. By using callbacks, Node.js can initiate tasks and continue executing other code without waiting. When the task completes, the corresponding callback is invoked, providing the result or error information. This approach enables concurrency and responsiveness in Node.js applications. However, alternative approaches like Promises and async/await have emerged to address the potential complexity of callback-based code.
What is the difference between Angular and Node.js?
It is a frontend development framework It is a server-side environment It is written in TypeScript It is written in C, C++ languages Used for building single-page, client-side web applications Used for building fast and scalable server-side networking applications Splits a web application into MVC components Generates database queries
What are the modules in Node.js?
Modules are like JavaScript libraries that can be used in a Node.js application to include a set of functions. To include a module in a Node.js application, use the require() function with the parentheses containing the module's name. Node.js has many modules to provide the basic functionality needed for a web application. Some of them include: HTTP Includes classes, methods, and events to create a Node.js HTTP server util Includes utility functions useful for developers fs Includes events, classes, and methods to deal with file I/O operations url Includes methods for URL parsing query string Includes methods to work with query string stream Includes methods to handle streaming data zlib Includes methods to compress or decompress files
Which database is more popularly used with Node.js?
MongoDB is the most common database used with Node.js. It is a NoSQL, cross-platform, document-oriented database that provides high performance, high availability, and easy scalability.
What is NPM?
NPM stands for Node Package Manager, responsible for managing all the packages and modules for Node.js. Node Package Manager provides two main functionalities: Provides online repositories for node.js packages/modules, which are searchable on search.nodejs.org Provides command-line utility to install Node.js packages and also manages Node.js versions and dependencies
What is Node.js? Where can you use it?
Node.js is an open-source, cross-platform JavaScript runtime environment and library to run web applications outside the client's browser. It is used to create server-side web applications. Node.js is perfect for data-intensive applications as it uses an asynchronous, event-driven model. You can use I/O intensive web applications like video streaming sites. You can also use it for developing: Real-time web applications, Network applications, General-purpose applications, and Distributed systems.
How is Node.js most frequently used?
Node.js is widely used in the following applications: Real-time chats Internet of Things Complex SPAs (Single-Page Applications) Real-time collaboration tools Streaming applications Microservices architecture
Why use Node.js?
Node.js makes building scalable network programs easy. Some of its advantages include: It is generally fast It rarely blocks It offers a unified programming language and data type Everything is asynchronous It yields great concurrency
What is the command used to import external libraries?
The "require" command is used for importing external libraries. For example - "var http=require ("HTTP")." This will load the HTTP library and the single exported object through the HTTP variable. Now that we have covered some of the important beginner-level Node.js interview questions let us look at some of the intermediate-level Node.js interview questions.
What are some of the most commonly used libraries in Node.js?
There are two commonly used libraries in Node.js: ExpressJS - Express is a flexible Node.js web application framework that provides a wide set of features to develop web and mobile applications. Mongoose - Mongoose is also a Node.js web application framework that makes it easy to connect an application to a database.
