NodeJS Interview Questions and Solutions – Set 1

NodeJS is an open-source and cross-platform runtime atmosphere constructed on Chrome’s V8 JavaScript engine for executing JavaScript code outdoors of a browser. It’s good to recollect that NodeJS isn’t a framework, and it’s not a programing language. It supplies an event-driven, non-blocking (asynchronous) I/O and cross-platform runtime atmosphere for constructing extremely scalable server-side functions utilizing JavaScript.

Node.js Interview Questions & Solutions

Let’s talk about some widespread questions that you need to put together for the interviews. These questions shall be useful in clearing the interviews specifically for the backend growth or full stack growth function. 

This set comprises the fundamental questions requested within the interview.

1. What’s Node.js?

Node.js is a JavaScript engine used for executing JavaScript code outdoors the browser. It’s usually used to construct the backend of the appliance and is extremely scalable.

2. What’s the distinction between Node.js and JavaScript?

JavaScript is a scripting language whereas Node.js is an engine that gives the runtime atmosphere to run JavaScript code.

  • JavaScript: It’s a light-weighted programming language (“scripting language”) used to develop interactive net pages. It could possibly insert dynamic textual content into the HTML parts. JavaScript is often known as the browser’s language.
  • Node.js: It’s used to run JavaScript packages outdoors the browser and it principally runs server-side code. It can’t be used to run HTML tags.

3. Is Node.js single-threaded?

Sure, Node.js is a single-threaded software as it’s constructed utilizing the single-threaded occasion loop mannequin structure.

4. What sort of API operate is supported by Node.js?

There are two forms of API capabilities supported by Node.js:

  • Synchronous: These API capabilities are used for non-blocking code.
  • Asynchronous: These API capabilities are used for blocking code.

5. What’s the distinction between Synchronous and Asynchronous capabilities?

  • Synchronous operate: These are the operate that block the execution of this system at any time when an operation is carried out. Therefore these are additionally referred to as blocking operations. We use these capabilities to carry out light-weight duties
  • Asynchronous operate: These are the operations that don’t block the execution of this system and every command is executed after the earlier command even when the earlier command has not computed the outcome. We use these capabilities to carry out heavy duties.

6. What’s a module in Node.js?

In Node.js Utility, a Module may be thought-about as a block of code that present a easy or complicated performance that may talk with exterior software. Modules may be organized in a single file or a group of a number of information/folders. Modules are helpful due to their reusability and skill to cut back the complexity of code into smaller items. Some examples of modules are. http, fs, os, path, and so on.

7. What’s npm and its benefits?

NPM stands for Node Package deal Supervisor. It’s a web-based repository for Node.js packages. We are able to set up these packages in our initiatives/functions utilizing the command line.

8. What’s middleware?

Middleware is the operate that works between the request and the response cycle. Middleware will get executed after the server receives the request and earlier than the controller sends the response.

9. How does Node.js deal with concurrency even after being single-threaded?

Node.js internally makes use of libuv library for dealing with all async name. This library creates a number of thread swimming pools to deal with async operations.

10. What’s management move in Node.js?

Management Move capabilities are executed at any time when there may be an async name made in this system. These capabilities outline the order wherein these asynchronous capabilities shall be executed.

11. What do you imply by occasion loop in Node.js?

Occasion Loop in Node.js is used to deal with callbacks. It’s useful in performing non-blocking I/O operations. An occasion loop is an limitless loop, which waits for duties, executes them, after which sleeps till it receives extra duties.

12. What’s the order wherein management move statements get executed?

The order wherein the statements are executed is as follows:

  • Execution and queue dealing with
  • Assortment of information and storing it
  • Dealing with concurrency
  • Executing the following traces of code

13. What are the primary disadvantages of Node.js?

Since Node.js is single-threaded so multi-threaded engines are higher and may deal with duties extra effectively. Additionally, we don’t use relational databases with Node.js like MySQL principally non-relational databases like MongoDB is used.

14. What’s REPL in Node.js?

REPL in Node.js stands for Learn, Consider, Print, and Loop. It’s a pc atmosphere just like the shell which is beneficial for writing and debugging code because it executes the code in on go.

15. Easy methods to import a module in Node.js?

We use the require module to import the Exterior libraries in Node.js. The outcome returned by require() is saved in a variable which is used to invoke the capabilities utilizing the dot notation.

16. What’s the distinction between Node.js and AJAX?

Node.js is a JavaScript runtime atmosphere that runs on the server facet whereas AJAX is a client-side programming language that runs on the browser.

17. What’s package deal.json in Node.js?

package deal.json is a file that’s used to retailer the metadata of all of the contents of the challenge. It’s used to explain the module used, run instructions, and different helpful details about the challenge.

18. Easy methods to write hiya world utilizing node.js?


const http = require('http');


http.createServer(operate (req, res) {

    res.write('Hi there World!'); 


}).pay attention(3000);

Run this program from the command line and see the output within the browser window. This program prints Hi there World on the browser when the browser sends a request by way of http://localhost:3000/.

19. What’s the hottest Node.js framework used nowadays?

Probably the most well-known Node.js framework used is Categorical.js as it’s extremely scalable, environment friendly, and requires only a few traces of code to create an software.

20. What are guarantees in Node.js?

A promise is mainly an development of callbacks in NodeJS. In different phrases, a promise is a JavaScript object which is used to deal with all of the asynchronous knowledge operations. Whereas creating an software you could encounter that you’re utilizing a whole lot of nested callback capabilities which causes an issue of callback hell. Guarantees resolve this drawback of callback hell.

Final Up to date :
24 Could, 2023

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