Hexon – Node JS Interview Questions

Here is the list of Node JS Interview Questions which are recently asked in Hexon company. These questions are included for both Freshers and Experienced professionals. Our Node JS Training has Answered all the below Questions.

1. What is an error-first callback in Node.js?

Error-First Callback in Node JS is a function which either returns an error object or any successful data returned by the function. The first argument is reserved for the error object. If any error has occurred during the execution of the function, it will be returned by the first argument.

2. Explain the purpose of module.exports?

When dividing the program code over multiple files, module. exports is used to publish variables and functions to the consumer of a module. The require() call in the source file is replaced with corresponding module. exports loaded from the module.

3. What do you understand by Reactor Pattern in Node.js?

Reactor Pattern is used to avoid the blocking of the Input/Outputoperations and provides with a handler that is associated with I/O operations. When the I/O requests are to be generated, they get submitted to a demultiplexer, which handles concurrency in avoiding the blocking of the I/O mode and collects the requests in form of an event and queues those events.

4. What’s the difference between ‘front-end’ and ‘back-end’ development?

Front and back end developers work on different sides of a website. Front end development is programming which focuses on the visual elements of a website or app that a user will interact with the client side. Back end development focuses on the side of a website user can't see (the server side)

5. What are LTS releases of Node.js?

LTS release status is "long-term support", which guarantees that critical bugs will be fixed for a total of 30 months. Production applications should only use Active LTS or Maintenance LTS releases.

6. List down the major security implementations within Node.js?

Validate user input to limit SQL injections and XSS attacks.
Implement strong authentication.
Avoid errors that reveal too much.
Run automatic vulnerability scanning.
Avoid data leaks.

7. Explain the concept of middleware in Node.js?

Middleware functions are functions that have access to the request object, the response object and the next function in the application's request-response cycle. The next function is a function in the Express router which, when invoked, executes the middleware succeeding the current middleware.

8. Explain the concept of URL module.

The 'url' module provides utilities for URL resolution and parsing. The getters and setters implement the properties of URL objects on the class prototype, and the URL class is available on the global object

9. Differentiate between spawn() and fork() methods in Node.js?

Differences between Spawn and Fork

Spawn is useful when we want to make a continuous data transfer in binary/encoding format — e.g. transferring a 1 Gigabyte video, image, or log file.
Fork is useful when we want to send individual messages — e.g. JSON or XML data messages.

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10. What do you understand by global objects in Node.js?

Global objects are global in nature and available in all modules and can be used directly. These objects are modules, functions, strings and object etc. Some of these objects aren't actually in the global scope but in the module scope.

11. Explain the concept of stub in Node.js.

Stubs are functions or programs that affect the behavior of components or modules that implements a pre-programmed responseStubs are dummy objects for testingcan be wrapped into existing functions. When we wrap a stub into the existing function the original function is not called.

12. How assert works in Node.js?

The assert module provides a set of assertion functions for verifying invariants. In assert() function, if the value is not truth, then a AssertionError is thrown with a message property set equal to the value of the message parameter

13. Explain the purpose of ExpressJS package?

Express JS basically helps to manage everything, from routes, to handling requests and views. Redis is a key/value store -- commonly used for sessions and caching in Node. js applications.

14. Explain the usage of a buffer class in Node.js?

The Buffer class in Node JS is designed to handle raw binary data. Each buffer corresponds to some raw memory allocated outside V8. Buffers act somewhat like arrays of integers, but aren't resizable and have a whole bunch of methods specifically for binary data.

15. How does Node.js handle the child threads?

16. Explain stream in Node.js along with its various types.

Streams are one of the fundamental concepts that power Node JS applications and used for data-handling method, to read or write input into output sequentially. There are four types of streams − Readable for read operation, Writable for write operation, Duplex for both read and write operation, Transform for where the output is computed based on input.

17. What is the use of NODE_ENV?

NODE_ENV is an environment variable popularized by the Express framework. It specifies the environment in which an application is running such as development, staging, production, testing, etc.

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TOP MNC's NODE JS INTERVIEW QUESTIONS & ANSWERS

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Hexon Node JS Interview Questions