Top Node.js Interview Questions You Must Prepare In 2021

Node.js is a popular server-side platform that is being adopted by an increasing number of businesses. It’s always a good idea to prepare and brush up on your interview skills if you’re considering a career move and have an upcoming job interview. Although there are a few general Node.js interview questions that come up in all types of interviews, we recommend that you focus your preparation on questions relevant to your business.

We’ve put up a comprehensive list of the most popular Node.js interview questions, as well as the best ways to respond to them. This will also assist you in understanding the basic concepts of Node.js.

Beginner Node.js Interview Questions

1. What is Node.js? Where can you use it?

Node.js is a cross-platform, open-source JavaScript runtime environment and library that allows web applications to be run outside of the client’s browser. It’s used to make web apps that run on the server.

Because it uses an asynchronous, event-driven approach, Node.js is ideal for data-intensive applications. You can use web apps that require a lot of I/O, such as video streaming sites. You can use it to create Real-time web apps, Network applications, General-purpose applications, and Distributed systems, among other things.

2. Why use Node.js?

Node.js makes building scalable network programs easy. Some of its advantages include:

  • It is generally fast
  • It rarely blocks
  • It offers a unified programming language and data type
  • Everything is asynchronous 
  • It yields great concurrency

3. How does Node.js work?

The workflow of a Node.js web server is often pretty similar to the diagram shown below. Let’s take a closer look at this process flow.

  • Clients send requests to the webserver to interact with the web application. Requests can be non-blocking or blocking:
  • Querying for data
  • Deleting data 
  • Updating the data
  • Node.js retrieves the incoming requests and adds those to the Event Queue
  • The requests are then passed one-by-one through the Event Loop. It checks if the requests are simple enough not to require any external resources
  • The Event Loop processes simple requests (non-blocking operations), such as I/O Polling, and returns the responses to the corresponding clients

A single thread from the Thread Pool is assigned to a single complex request. This thread is responsible for completing a particular blocking request by accessing external resources, such as computation, database, file system, etc.

Once the task is carried out completely, the response is sent to the Event Loop that sends that response back to the client.

4.What are the two types of API functions in Node.js?

The two types of API functions in Node.js are

  • Asynchronous, non-blocking functions
  • Synchronous, blocking functions

5. Why is Node.js Single-threaded?

Node.js is single-threaded for async processing. By doing async processing on a single-thread under typical web loads, more performance and scalability can be achieved instead of the typical thread-based implementation.

6. What is control flow function?

A generic piece of code which runs in between several asynchronous function calls is known as control flow function.

7. Explain callback in Node.js.

After completing a task, a callback function is invoked. It prevents any blockage by allowing other code to run in the interim. Because Node.js is an asynchronous platform, it primarily relies on callbacks. Callbacks are supported by all of Node’s APIs.

8. Can you access DOM in node?

No, you cannot access DOM in node.

9. How would you define the term I/O? 

  • The term I/O is used to describe any program, operation, or device that transfers data to or from a medium and to or from another medium
  • Every transfer is an output from one medium and an input into another. The medium can be a physical device, network, or files within a system
io

10. How is Node.js most frequently used?

Node.js is widely used in the following applications:

  1. Real-time chats
  2. Internet of Things
  3. Complex SPAs (Single-Page Applications)
  4. Real-time collaboration tools
  5. Streaming applications
  6. Microservices architecture

11. Mention the steps by which you can async in Node.js?

By following steps you can async Node.js

  • First class functions
  • Function composition
  • Callback Counters
  • Event loops

12. Explain the difference between frontend and backend development?

Front-endBack-end
Frontend refers to the client-side of an applicationBackend refers to the server-side of an application
It is the part of a web application that users can see and interact withIt constitutes everything that happens behind the scenes
It typically includes everything that attributes to the visual aspects of a web applicationIt generally includes a web server that communicates with a database to serve requests
HTML, CSS, JavaScript, AngularJS, and ReactJS are some of the essentials of frontend developmentJava, PHP, Python, and Node.js are some of the backend development technologies

13. What is NPM?

NPM stands for Node Package Manager, responsible for managing all the packages and modules for Node.js.

Node Package Manager provides two main functionalities:

  • Provides online repositories for node.js packages/modules, which are searchable on search.nodejs.org
  • Provides command-line utility to install Node.js packages and also manages Node.js versions and dependencies  

14. How Node.js overcomes the problem of blocking of I/O operations?

Node.js solves this problem by putting the event based model at its core, using an event loop instead of threads.

15. Why is Node.js preferred over other backend technologies like Java and PHP?

Some of the reasons why Node.js is preferred include:

  • Node.js is very fast
  • Node Package Manager has over 50,000 bundles available at the developer’s disposal
  • Perfect for data-intensive, real-time web applications, as Node.js never waits for an API to return data
  • Better synchronization of code between server and client due to same code base
  • Easy for web developers to start using Node.js in their projects as it is a JavaScript library

16. What is the difference between Angular and Node.js?

AngularNode.js
It is a frontend development frameworkIt is a server-side environment
It is written in TypeScriptIt is written in C, C++ languages
Used for building single-page, client-side web applicationsUsed for building fast and scalable server-side networking applications
Splits a web application into MVC componentsGenerates database queries

17. Which database is more popularly used with Node.js?

MongoDB is the most common database used with Node.js. It is a NoSQL, cross-platform, document-oriented database that provides high performance, high availability, and easy scalability.

18. What is the difference between Node.js vs Ajax?

The distinction between Node.js and Ajax is that Ajax (short for Asynchronous Javascript and XML) is a client-side technology that is frequently used to update the contents of a page without having to refresh it. Node.js, on the other hand, is a server-side Javascript that is used to construct server software. The server, rather than the browser, executes Node.js.

19. What are some of the most commonly used libraries in Node.js?

There are two commonly used libraries in Node.js:

  • ExpressJS – Express is a flexible Node.js web application framework that provides a wide set of features to develop web and mobile applications.
  • Mongoose – Mongoose is also a Node.js web application framework that makes it easy to connect an application to a database.

20. What are the pros and cons of Node.js?

Node.js ProsNode.js Cons
Fast processing and an event-based modelNot suitable for heavy computational tasks
Uses JavaScript, which is well-known amongst developersUsing callback is complex since you end up with several nested callbacks
Node Package Manager has over 50,000 packages that provide the functionality to an applicationDealing with relational databases is not a good option for Node.js
Best suited for streaming huge amounts of data and I/O intensive operationsSince Node.js is single-threaded, CPU intensive tasks are not its strong suit

21) What is the command that is used in node.js to import external libraries?

Command “require” is used for importing external libraries, for example, “var http=require (“http”)”. This will load the http library and the single exported object through the http variable.

22. Mention the framework most commonly used in node.js?

“Express” is the most common framework used in node.js.

23. What is ‘Callback’ in node.js?

In node.js, the callback function is used to handle numerous requests to the server. For example, if you have a large file that will take a long time for a server to read and you don’t want the server to be preoccupied with reading that large file while dealing with other requests, you can use the call back method. The call back function allows the server to process pending requests first and then call a function once they are complete.

24. What are the Challenges with Node.js?

Emphasizing on the technical side, it’s a bit of challenge in Node.js to have one process with one thread to scale up on multi core server.

I believe that these Node.js interview questions would help you understand what kind of questions may be asked to you in an interview, and by going through these Node.js interview questions, you can prepare and crack your next interview in one go.

Best of luck with your upcoming job interview!

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