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Node.js Interview Questions and Answers

Node.js Interview Questions and Answers

Node.js, the server-side scripting application, uses JavaScript – a language that's common among millions of developers across the world – meaning it has a far smaller learning curve except among utter beginners. Using Node.js, one can create anything from basic command-line programs to the sophisticated cloud applications at the industry level with absolute ease.

That's why most companies demand that a Professional Node.js Developer handle the entire server-side. Node.js, offers work opportunities at various stages, too. In case you plan to hold interviews with Node.js in the near future, we are here to support you with a list of top 30+ node.js interview questions and answers you need to schedule in 2020-21.

Before I begin this article on Node.js Interview Questions, let me give a message to the readers who may have attended interviews with Node.js in the recent past. So, if you've come across these questions that have been posted in interviews but are absent in this post, please feel free to add such questions in the section on the comments below. We're going to try to answer those early so that others will profit from it too.

A list of interview questions and answers from top frequently asked Node.js is provided below.

1. What is Node.js?

Node.js is server-side scripting used to construct scalable programs. It is a web application framework based on the JavaScript Engine used by Google Chrome. It runs on Mac OS, Windows, and Linux without any modifications within Node.js runtime. This runtime can allow the execution of a JavaScript application on any platform outside of a browser.

2. What is the purpose of Node.js?

These are the following purposes of Node.js:

  1. Real-time web applications
  2. Network applications
  3. Distributed systems
  4. General purpose applications

3. Is Node.js free to use?

Yes. It is published and is free to use under MIT license.

4. Is Node a single threaded application?

Yes. Node is a single-threaded, event looping application.

5. What are the advantages of Node.js?

The key benefits of Node.js follow:s

  1. Node.js is asynchronous, and is powered by events. Any API? Node.js library is non-blocked, and its server does not wait until the API returns the data. After calling it, it moves to the next API, and a Node.js Events notification mechanism responds to the server from the previous API call.
  2. Node.js is fast because it's based on Google Chrome? S V8 engine with JavaScript. Its library executes code very fast.
  3. Node.js is heavily scalable but single-threaded.
  4. Node.js has no buffering facility. The application will never buffer up data. The data is output in chunks.

6.What is npm?

Node Package Manager stands for npm. Npm has two primary functionalities:

  1. Online node.js repositories for packages / modules searchable at search.nodejs.org
  2. Command line utility for installing packages, managing versions, and managing dependencies of Node.js packages.

7. What is REPL in context of Node?

REPL stands for Read Eval Print Loop, and describes a programming environment such as a window console or unix / linux shell where a command is entered and device responds with an output. Node.js, or Node, is bundled with REPL. It carries out the tasks it desires.

  • Read − Read the input of the user, translate the input into the data structure of JavaScript and store it in memory.
  • Eval − Takes and evaluates the Print data structure
  • Prints- the Loop output
  • Loops- the above command until the user twice presses ctrl-c.

8.What is the use of Underscore variable in REPL?

Use _ to get the last result.

> var a = 15
> var b = 25
> a + b
> var sum = _
> console.log(sum)

9. What is local installation of dependencies?

By default npm is installing any local mode dependency. Local mode here refers to the installation of the package in the directory node modules lying in the folder where the application Node is located. Packages deployed locally are made available via require(). The syntax is to install a Node project following locally.

C:\Nodejs_WorkSpace>npm install express

10. 1What is Package.json?

Package.json is in the root directory of any application / module Node and is used to describe package properties.

11. What is error-first callback?

Error-first callbacks are used to pass data and errors on. If something goes wrong, the programmer must check the first argument, since it is always an argument for error. Data is passed with additional arguments.

fs.readFile(filePath, function(err, data) {    
if (err) {  
//handle the error  
// use the data object  

12. Why node.js is quickly gaining attention from JAVA programmers?

Node.js is getting quick attention as it is a JavaScript loop-based server. Node.js gives users the ability to write on the server the JavaScript that has access to things like HTTP stack, I / O file, TCP and databases.

13. Does Node.js provide Debugger?

Yes, Node.js provides a simple protocol based on TCP and a built-in debug client. You can use debug argument for debugging your JavaScript file, followed by the name of the js file that you want to debug.

14. What types of tasks can be done asynchronously using the event loop?

  1. I/O operations
  2. Heavy computation
  3. Anything requiring blocking

15.What is a control flow function?

Control flow feature is a generic piece of code running between multiple asynchronous calls to operate.

16. How "Control Flow" controls the functions calls?

The control flow functions as follows:

  • Control the order of execution
  • Collect data
  • Limit concurrency
  • Call the next step in a program

17. What is the main functionality of npm?

Following are the two main functionalities of npm:

  • Online node.js repositories for packages / modules which can be searched at search.nodejs.org
  • Command line utility for installing packages, managing versions, and managing dependencies of Node.js packages.

18. What is purpose of Buffer class in Node?

Buffer class is a global class, which can be accessed without importing buffer module in the program. A Buffer is a kind of integer array and refers to an allocation of raw memory outside the V8 heap. Unable to resize a buffer.

19. Which module is used for web based operations?

Web-based operations use http module.

var http = require("http")

20. What are streams?

Streams are objects that allow you to continuously read data from a source, or write data to a destination.

21. How many types of streams are present in Node.

There are four types of streams within Node.js.

  • Readable − Stream used in read operation.
  • Writable − Stream for write service.
  • Duplex − Stream that can be used for both write and read operations.
  • Transform − A type of duplex stream, where input-based output is measured.

22. What is Chaining in Node?

Chanining is a method for linking output from one stream to another stream and establishing a multiple operating chain for the source. Typically used when piping.

23. Does Node.js supports cryptography?

Yes, crypto module Node.js supports cryptography. It provides cryptographic functionality which includes a collection of wrappers for the HMAC, encrypt, decode, sign and verify hash functions of open SSL. For instance:

const crypto = require('crypto');    
const secret = 'uvwxyz';    
const hash = crypto.createHmac('pre653', secret)    
.update('Welcome to phptpoint')    

24. What is the main difference between programmer errors and operational?

Operational errors are not bugs that cause device problems such as request timeout or hardware failure. The programmer errors, on the other hand, are actual bugs.

25. What is the role of assert in Node.js?

The Assert Node.js is a form of writing tests. It does not provide feedback if your test runs unless one fails. The module assert includes a basic collection of statement checks which can be used to evaluate invariants. The module is intended for internal use by Node.js, but can be used via require ('assert') in the application code. For instance:

var db = require('db');    
function add (x, y) {    
  return x + y;    
var expected = add(5,3);    
assert( expected === 8, 'five plus three is eight');

26. What is the Punycode in Node.js?

The Punycode is an encoding syntax which is used to convert character string Unicode (UTF-8) to character string ASCII. It's bundled with v0.6.2 and later versions of Node.js. If you wish to use it with other versions of Node.js, use npm first to install the Punycode module. To access it, you must use the require ('Punycode')

punycode = require('punycode');