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.

Q21. Why we have to keep separate Express app and server?

Express app encapsulates your API logical, which is your data abstraction. This is where you should keep up your DB logic or data models.

The server should be differently handled as its sole responsibility is to keep the app/website running. The separation of concerns will lead to optimization.

Q22. What is the difference between setImmediate() and setTimeout()?

setImmediate() executes a script once the current poll or the event loop phase has completed.

setTimeout() is used to schedule scripts to be run after a minimum threshold has elapsed.

The order in which these timers are executed varies on the context in which they are used. If both are called from within the module, timing will be bound by the process performance.

Q23. How does Passport handle authorization?
Passport is an authentication middleware that is extremely flexible and modular. Any application might need to incorporate a user's information through third-party services. In this particular case, the application will send out a "connect" request with the user's Twitter or Facebook accounts.

Authorization is handled by calling passport.authorize(). If the authorization is granted, the result by the verify callback shall be assigned to the req.account.

Here's how authorization of a Twitter account is handled in Passport.


  passport.authorize('twitter-authz', { failureRedirect: '/account' })

  passport.authorize('twitter-authz', { failureRedirect: '/account' }),
  function(req, res) {
    var user = req.user;
    var account = req.account;

    account.userId =; {
      if (err) { return self.error(err); }

Q24. How Node.js and JavaScript are related?

Node.js appeared when the engineers of JavaScript expanded it from something you could just keep running in the browser to something you could keep running on your machine as an independent application. The Node run-time environment incorporates all that you have to execute a program written in JavaScript.

Q25. How do you make node JS secure?

Here are some best practices to make your NodeJS application secure:

  • Limit the number of concurrent requests through middleware such as cloud firewalls, cloud load balancers, etc.
  • Adjust the HTTP response using secure headers for enhanced security and blocking vulnerabilities such as XSS, clickjacking, etc.
  • Use a secure hash + salt function such as bcrypt to store passwords, API keys, and secrets instead of Node.js crypto library.
  • Limit brute-force authorization attacks by limiting the number of failed login attempts and, in such a case, ban the user's IP address.
  • Limit your payload size by using a reverse-proxy or a middleware.
  • Avoid pushing secrets on to the npm registry.
  • Use cookies securely
  • Ensure the security of all your dependencies
Q26. In Node.js, which framework is used commonly?

Hapi.js or Express.js is robust and modular for developing the APIs. It has input validation, configuration functioning, and many other features.

Q27. What is Express js?

Express js is a type of framework which is used for node js. It released under the MIT License. It helps to manage a server and routes. It is also designed for building web applications and APIs.

It was founded by TJ Holowaychuk. The first release of express js was on the 22nd of May, 2010. Version 0.12.0.

Features of Express framework:
  • It can be used to design single-page or multi-page web applications.
  • It helps to setup middlewares to respond to HTTP Requests.
  • It helps us to render HTML Pages dynamically.
Q28. What is the command for import external libraries in Node JS?

Command “require” is used in Node JS for import external libraries. Mentioned below is an example of this. “var http=require (“http”)”. This will load the library and the single exported object through the HTTP variable.

Q29. What is the purpose of module.exports in Node.js?

In Node.JS, module.exports is a special object that is included in every JavaScript file present in the Node.JS file default. Here module is a variable that represents the current module, and export is the object that will be exposed as the module.

Here we export a string from testYourModule.js file


// testYourModule.js
module.exports = "Best Interview Questions provides an example of module.exports"

// index.js
const params = require('./testYourModule.js')
console.log(params )

Q30. What are Global objects, and how do you use it in node JS?

Global objects are those who provide variables and functions that are available anywhere within the code. By default, they are those objects which are built into the language or the environment.

All the properties of Global Objects can be accessed directly in node.js using the window.


window.currentUser = {
    name: "Best Interview Question"

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...