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Node.JS Interview Questions And Answers

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by Priyanka Vatsa
Last modified: July 15th 2021

If you're looking for Node.JS Interview Questions for Experienced or Beginners, you are at the right place. There are a lot of opportunities from many reputed companies in the world. According to research, Node.JS has a market share of about 2.6%. So, You still have the opportunity to move ahead in your career in Node.JS Development. Mindmajix offers Advanced Node JS Interview Questions 2021 or node js programming interview questions that help you in cracking your interview & acquire a dream career as Node.JS Developer.

Types of Node.JS Interview Questions

Top 10 Frequently Asked Node.js Interview Questions

  1. What is NodeJS?
  2. Node JS Vs Ruby
  3. What is a Javascript Engine?
  4. What are the common Modules?
  5. Difference between the cluster and child_process modules?
  6. What is REPL? 
  7. What is the latest version of NodeJS?
  8. What is the cluster?
  9. What are the types of versions available?
  10. What are event listeners?
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Node.js Interview Questions for Freshers

1) What is NodeJS?

Node.js can be simply explained as it is a concept of two outcomes: runtime environment and JavaScript library. So basically, node.js will enable you to use javascript beyond the browser. It can make Javascript like 'go anywhere Javascript'.

2) What is NPM?

Javascript operates in a runtime environment with the help of node js having its own package manager, this package manager is called NPM.

3) What is CLI in Node.js?

One of the vital reasons for Node.js getting popular is its 900000 packages connected to a large ecosystem. CLI is a command-line interface that will allow you to automate your tasks by taking advantage of this vast ecosystem. Not only that, by writing CLI you can differentiate your proposed packages among the ecosystem.

4) In which Language Node Js is written?

Node.js shows compatibility with three types of language 

  1. C
  2. C++
  3. Javascript 

5) Who is the author of Node Js?

Ryan Dahl is the author of Node.js it was almost 13 years back when the javascript environment was introduced to the world. Initially, Node is was supported by Linux and Mac OS X but later it was sponsored by Joyent.

6) What is a Javascript Engine?

Javascript engine is used to run the java code in the browser so you can define a javascript engine as a computer program that is used to perform the java code. Initially, it was just used for interpretation and progressively it improved and got evolved. Generally, all browsers have one dealer and he is the one who develops the javascript engine.

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7) What is a V8 Engine?

In 2008 when google chrome was launched time chrome also introduced its project of the V8 engine. It is an open-source network that can be written in the c++ language.

8) What is ECMAScript?

Ecmascript first appeared in 1997, which was specified and developed by Esma internationals. Evmascriot is also a programming language, which developed various other scripts like Jscript, ActionScript, and the most popularly used javascript.

9) How can you check the installed version of Node Js?

For that, you need to install NPM which is a package manager. The second thing you will need is to have a node in your computer, you can check installed NPM and node by just typing simple commands. Now carry the following steps

  • Open the windows command prompt

  • Open command-line tool line Babun, Powershell, ConEmu, etc.

  • Type node-v which will display your current version of Node Js.

10) What are Modules in Node Js?

Modulus is various commands used in node js to perform tasks like addition, subtraction, division, multiplication, etc. Ins short you can do maths in js using modulus.

11) What are the common Modules?

Arithmetic operations ( addition, subtraction, multiplication, division), exponentials, increment, and decrement are various common modulus in js.

12) What require() is used in Node Js?

Modulus is operated by two main managing modules 

  • The Require module

  • The module module

Both of them are available on a global scope.

13) What the module. exports in Node Js?

The module. exports is a default application that can be found in every js file of Node js.

14) Is Node Js Single-threaded?

Node Js is single-threaded but it is non-blocking as well, it means that while operating node js various functions like callbacks is carried out in the background which is carried out using different threads or multiple threads.

15) Node JS Vs Ruby

Feature Node JS Ruby On Rails
Written In C, C++, JavaScript Ruby
Operating System Solaris, OpenBSD,  FreeBSD, Linux, Mac, MS, webOS and nonstops Cross-Platform
Type Event-driven networking Web application framework
License MIT MIT
Performance High Low
Popularity Popular for its features Yet to be popular
Documentation Available Lack of documentation
Consistency Inconsistent Consistent structure
Complexity Easy to implement Complex implementation

16) What are the events?

  • The event can be explained as activities carried out. For example, when you open a file it is an event when you close a file it is an event.

  • In Node js, there is a defaulted module named "Events" with which you can carry various activities like create, fire, listen, etc.

17) What the event loop in Node Js?

Non-blocking operations in Node Js are carried out with the help of the event loop.

18) How to create a simple server in Node js that returns Hello World?

Certain steps are needed to be carried out for this operation:

  • Import the module which is required.

  • Create the server using HTTP.createServer().

  • Test the request and wait for a response 

19) Difference between the cluster and child_process modules?

  • A cluster is when one master program is running two or more nodes at a single running time.
  • A child process simply starts a new script on the system, it is quite similar to the cluster but in a different language.

20) How to stop the master process without suspending all of its child processes?

Upstart is a process management system with which you can stop the master process. Generally when the master process is stopped or killed the child process still continues to work.

21) What does an emitter do and what is a dispatcher?

The emitter is one that makes communication between two nodes.

When the job of the scheduler is completed in a program then dispatched comes into the frame and takes the task to the desired status.

Node.js Interview Questions for Experienced

22) Since the node is a single-threaded process, how to make use of all CPUs?

The node js is single-threaded but the node name itself suggests that it is a topology, which means there is communication between two nodes. This communication between the two nodes makes use of all CPUs.

23) Syntax to install modules using NPM.

Syntax : $ npm install

Example: 

$ npm install express
var express = (‘express’);
Where express is the Name of the module,
express is a JS file, that can be used in your module.

24) Mention types of npm modules available that are used very often.

Express, connect, socket.io and SockeJS, pug, MongoDB and Mongojs, Redis, Lodash, forever, bluebird, moment are some of the npm modules.

25) Command to list modules installed in current npm

$ npm ls

Note: Remember not to mention npm in UPPERCASE - (Recommended)

26) What are the attributes of package.json

Name, version, description, homepage, author, contributors, dependencies − list of dependencies, repository − repository type and URL of the package, the main − entry point of the package, keywords.

27) What is REPL?

REPL - Read, Eval, Print, Loop.
It is an environment for input commands to perform REPL tasks. Each of the tasks is associated with its respective operations.

28) What kind of applications can be built by Node.JS.

DIRT, JSON, I/O Bound, Single Page applications are preferable to use Node.JS.

29) What is the latest version of NodeJS?

Node v16.3.0 is the current version.

30) NodeJS is a framework. True or False.

False. It is runtime or environment, but not a framework.

31) Commands to work with the file from the local database.

Var fs = require(‘fs’);

Read: fs.readFile();
Create:
fs.appendFile();
fs.open();
fs.writeFile();
Write: fs. writeFile();
Delete: fs.unlink();
Rename: fs.rename();
Update:
fs.appendFile()
fs.writeFile()

32) What is an error-first callback in Node JS?

In order to check for the proper working of the code, we need to verify error-free execution. In this regard, error-first callbacks are used, which will send error first, followed by related data to the error.

33) What is the cluster?

Cluster is a process to handle thread execution load while working with multi-core systems.

34) Why node is single-threaded?

In order to upgrade the performance well, single thread operations work better than multi-threaded operations. 

35) How does the URL module work?

This module helps URL to parse it into host, pathname, search, query, etc.

Example:

var url = require('url');
var adr = 'https://mindmajix.com/?s=node+js+training';
var q = url.parse(adr, true);
console.log(q.host); //returns 'mindmajix.com'
console.log(q.search); //returns '?s=node+js+training'

36) What is the use of the Nodemailer module.

It is not included in the default modules list, it has to be installed using npm.
Var nodemailer = require(‘nodemailer’);

37) What are the types of versions available?

Patch_Version, Minor_Version, Major_Version.

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38) What are event emitters in NodeJS?

Objects in NodeJS will have to trigger events in order to maintain the asynchronous execution of the core API used. These objects that emit events are known as Event Emitters.

39) What are event listeners?

Events that are emitted by event emitters have to listen in order to continue the asynchronous execution of the threads. These objects that listen to the emitted events are known as listeners.

About Author

author
NamePriyanka Vatsa
Author Bio

Priyanka Vatsa is a Senior Content writer with more than five years’ worth of experience in writing for Mindmajix on various IT platforms such as Palo Alto Networks, Microsoft Dynamics 365, Siebel, CCNA, Git, and Nodejs. She was involved in projects on these technologies in the past, and now, she regularly produces content on them. Reach out to her via LinkedIn and Twitter.