Node.js Interview Questions and Answers

Last updated on Apr 07, 2023
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Node js Interview Questions

In this world full of development firms we all know how useful Server Side Scripting is. Node.JS is also server-side scripting with the help of which you can build anything, starting from a single program to a complex web application. And that’s why Certified Node.JS developers are in too high demand. Node.JS opens many opportunities for you and to grab you those opportunities we have compiled a popular list of Node.JS Interview Questions and Answers. These questions will also help you to clear all your basic concepts of Node.JS.

It is a web application framework that is built on Google Chrome Javascript’s Engine that compiles JavaScript into machine code and reduces development costs by 58%. This backend framework has been worldwide accepted and can be used in real-time web applications, network applications, single-page applications, etc. In the year 2018, this framework hits 1 billion downloads and you will be surprised to know that Node js powers over 30 million sites out of which 6.3 million sites are from the U.S alone. Developers who are looking for a change and want to give their career a boost, we assure you this list of interview questions surely uplift your confidence.

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Most Frequently Asked Node.js Interview Questions

Here in this article, we will be listing frequently asked Node js Interview Questions and Answers with the belief that they will be helpful for you to gain higher marks. Also, to let you know that this article has been written under the guidance of industry professionals and covered all the current competencies.

Q41. What is the use of CORS in Node JS?

CORS is a Node.js package used for providing a Connect/Express middleware.


app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");

Q42. Why is the importance of a consistent style? What tools can help you assure a consistent style?

Consistent style can help your team members modify projects easily without the need to learn a new style for every project. Some of the useful tools are Standard and ESLint.

Q43. What are the global installations of dependencies?

They have globally installed packages or dependencies that are stored in the /npm directory. These dependencies can be used in Command Line Interface (CLI) of any node.js. However, they cannot be imported using require () command in Node application directly. In order to install a Node project globally, you need to use -g flag.

Q44. What are the local installations of dependencies?

Local mode is the package installation in the node-modules directory in the same folder where Node application is stored. By default, the Node Package Manager (NPM) installs dependencies in the local mode. Most locally deployed packages are also accessible via require(). In order to install a Node project locally, you need to follow the syntax.

Q45. What is EventEmitter in Node.js?

EventEmitter class lies in the events module and is accessibly through the following syntax:

//import events module
var events = require('events');
//create an eventEmitter object
var eventEmitter = new events.EventEmitter();

In case an EventEmitter instance is facing error, it emits 'error' event. When a new listener is added, the 'newListener' event gets fired and when a listener gets removed, 'removeListener' event gets fired.

nodejs interview questions

Q46. What is V8 Engine in Node JS?

V8 Engine is Google's open-source javascript and written in C++. It is used inside Google Chrome. It was first designed to increase the performance of JavaScript execution inside web browsers.

Q47. Why node is faster than others?

Multiple reasons are listed below:

  • In the comparison of HTTP servers, it provides the non-blocking of the input/output.
  • Node reduces the total number of servers that serve an equal amount of requests.
  • This uses the single process for managing the multiple requests.
  • By using the single-thread process, the computing speed will get increased and it also saves a lot of space.
Q48. Why we used async & await?

Async and await are used to make the code easier to write and read. Also, the agenda behind rolling out this feature is to deal with the promises and functions chaining in the Node. Where the functions do not need to be chained just one after another, simply call the await function that returns the promise. On the other hand, the function async should be declared before returning a promise by awaiting a function.

Q49. Why we use express in node JS?

ExpressJS is one prebuilt framework of NodeJS that can assist the users in building server-side web apps faster plus smarter. Simplicity, flexibility, minimalism, scalability are a few of its many characteristics and as it is built inside NodeJS itself, Express inherited its execution as well.

ExpressJS streamlined coding in Node JS to a great extent and provided programmers some extra features to increase their coding of the server-side. There is no doubt in the fact that it is the most famous frameworks of all in today’s time.

Q50. What is REST API in node JS?

Representational State Transfer or REST is a standard web-based architecture. REST makes use of the HTTP Protocol. It twirls around resources where each and every element is one resource and the resource is obtained by the common interface with the help of standard HTTP methods. This was first proposed by a man named Roy Fielding in the year 2000. The REST Server solely renders entrance to resources as well as REST client accesses plus modifies these resources with the help of the HTTP protocol. And here each and every resource is recognized by URIs or by global IDs. It uses numerous representations to present the resource such as text, or JSON, or XML, etc.

Top 20 Node.js Interview Questions

  • Is Nodejs asynchronous?
  • What are the advantages and disadvantages of node JS?
  • What is Closure in Node.js?
  • What are authentication and authorization in node JS?
  • What is Event Loop?
  • Explain Synchronous vs Asynchronous Javascript?
  • Why node is faster than other programming languages?
  • Why we used async & await in Node.js?
  • What are the promises and how do they work?
  • Why is Node.js single-threaded?
  • What is buffer and stream in Node.js?
  • What is callback hell and how can it be avoided?
  • What is Express?
  • What is Middleware?
  • What do you mean by REST API?
  • Why is Node.js so popular for REST API?
  • How do you authenticate API in node JS?
  • What are blocking and non-blocking in Node.js?
  • Why is a node called a non-blocking model?
  • What is Closure?
Quick Facts About Node.js
What is the latest version of Node.js? 15.14 / 15th January 2021.
When was Node.js first released? 27th May 2009
Who is the Author of Node JS? Ryan Dahl
What language is used in Node JS? C, C++, JavaScript
Node.js License MIT License
Operating system Windows, SmartOS, Linux, macOS, Microsoft, FreeBSD, OpenBSD

Being a developer we know that Node.JS is a very vast topic that includes questions of all levels like Fresher, Intermediate, and Advanced level. Reading all questions just before one day of your interview wouldn’t make any sense and that results in more nervousness. This area requires a lot of constant practice and practical experience.

After practicing different questions, try to solve sample papers and some Node MCQ from different websites which will tell you your current progress and area that still requires improvement.

Reviewed and verified by Umesh Singh
Umesh Singh

My name is Umesh Singh having 11+ experience in Node.JS, React JS, Angular JS, Next JS, PHP, Laravel, WordPress, MySQL, Oracle, JavaScript, HTML and CSS etc. I have worked on around 30+ projects. I lo...