NodeJS Interview Questions and Solutions – Set 1


NodeJS is an open-source and cross-platform runtime setting constructed on Chrome’s V8 JavaScript engine for executing JavaScript code exterior of a browser. That you must 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 setting for constructing extremely scalable server-side purposes utilizing JavaScript.

Node.js Interview Questions & Solutions

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

This set incorporates the fundamental questions requested within the interview.

1. What’s Node.js?

Node.js is a JavaScript engine used for executing JavaScript code exterior the browser. It’s usually used to construct the backend of the applying and is very 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 setting to run JavaScript code.

  • JavaScript: It’s a light-weighted programming language (“scripting language”) used to develop interactive net pages. It might probably insert dynamic textual content into the HTML components. JavaScript is often known as the browser’s language.
  • Node.js: It’s used to run JavaScript packages exterior the browser and it largely 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 utility 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 sorts 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 each time 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 Software, a Module could be thought-about as a block of code that present a easy or complicated performance that may talk with exterior utility. Modules could be organized in a single file or a group of a number of recordsdata/folders. Modules are helpful due to their reusability and talent to scale back the complexity of code into smaller items. Some examples of modules are. http, fs, os, path, and many others.

7. What’s npm and its benefits?

NPM stands for Node Bundle Supervisor. It’s a web based repository for Node.js packages. We are able to set up these packages in our tasks/purposes 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 stream in Node.js?

Management Move capabilities are executed each time there’s an async name made in this system. These capabilities outline the order through which these asynchronous capabilities can 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 countless loop, which waits for duties, executes them, after which sleeps till it receives extra duties.

12. What’s the order through which management stream statements get executed?

The order through which the statements are executed is as follows:

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

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

Since Node.js is single-threaded so multi-threaded engines are higher and might deal with duties extra effectively. Additionally, we don’t use relational databases with Node.js like MySQL largely 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 setting much like the shell which is beneficial for writing and debugging code because it executes the code in on go.

15. How one can 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 setting 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 mission. It’s used to explain the module used, run instructions, and different helpful details about the mission.

18. How one can write howdy world utilizing node.js?


const http = require('http');


http.createServer(operate (req, res) {

    res.write('Hiya World!'); 


}).pay attention(3000);

Run this program from the command line and see the output within the browser window. This program prints Hiya 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?

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

20. What are guarantees in Node.js?

A promise is principally 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 information operations. Whereas growing an utility chances are you’ll encounter that you’re utilizing numerous nested callback capabilities which causes an issue of callback hell. Guarantees clear up this downside of callback hell.

Final Up to date :
24 Could, 2023

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