Top 50+Nodejs Interview Question and Answer 2024

Ideas earlier than you attend Node.JS an interview

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Node.js is a in style server-side platform utilized by many corporations. In case you are making ready for a profession change, it’s all the time a good suggestion to brush up in your interview abilities beforehand. Though there are a couple of generally requested Node.js interview questions that you just would possibly concentrate on, we additionally advocate you to deal with unique Node.js interview questions.

We’ve got compiled a listing of Node.js interview questions that come up usually in interviews and likewise provide help to perceive the basic ideas of Node.js.

Newbie’s NodeJS interview questions

1) What’s nodeJS

NodeJS or node is an open-source and cross-platform runtime surroundings that’s constructed on Chrome’s V8 engine (which is written in c++) for executing JavaScript code outdoors of the browser.

JavaScript runs within the browser it might solely entry your net web page however once you permit it to run in your machine with NodeJS we simply created a complete new world the place js can entry the file system, Occasions, OS, and different methods core module.

typically, we use to construct back-end companies or API additionally referred to as (software programming interfaces) these are the companies that energy our consumer purposes like an online app operating inside an online browser or a cellular software.

Corporations like’s Netflix, LinkedIn, Uber, and lots of extra makes use of nodeJS js for managing their companies.

So at present javaScript can also be a back-end in addition to the front-end programming language.

2) What are the information sorts in Node.js? Primitive Sorts.

Nodejs is constructed on high of JavaScript so many of the information kind that current in JavaScript can also be current in Nodejs.

String -> It include set of characters that may additionally include areas and numbers for instance

const string1 = “A string primitive”;

const string2 = ‘i’m string too’;

const string3 = `quantity like 1,2,3 are additionally a instance of string`;

Quantity → by default each worth is float information kind.

const num = 2;

Boolean → true or false.

const num = true;

const num2 = false;

Undefined → worth if not assigned to the variable.

const num; // num is undefined.

Null → absence of object worth.

nodejs has yet another further information kind which isn’t accessible within the browser’s JavaScript

Buffer → Buffer is principally used to retailer binary information.

3) What’s callback hell in Node.js?

Callback hell is an occasion when a developer tries to execute a number of asynchronous operations one after the opposite.

aync_Callback1(operate () {

aync_Callback2(operate () {

aync_Callback3(operate () {

aync_Callback4(operate () {

})

4) How will you stop CallBack hell?

Methods for avoiding callback hell

Utilizing Async.js

is a very fashionable utility module for dealing with Asynchronous callbacks.

Additionally, this utility module is obtainable for JavaScript.

Async.js -> https://www.npmjs.com/package/async

command -> npm set up async

Utilizing Guarantees

Guarantees provide an affiliate an alternate technique to write async code. They both come the outcomes of execution or the error/exception. Implementing ensures wants the utilization of <.then()> carry out that waits for the promise object to come back. It takes 2 nonobligatory arguments, every operate. trying on the state of the promise simply one in every of them can get known as. the first name payoff if the promise will get consummated. Nonetheless, if the promise will get rejected, then the second efficiency can get known as.

5) Are you able to entry DOM within the node?

No, you can’t entry DOM(doc object mannequin) in node.

6) When Ought to We Use Node.Js?

-> NodeJS is usually used once we are constructing methods that require a excessive variety of I/O operations. Like saving information to DataBase, recordsdata entry.

For instance :

IoT Purposes
Video Streaming.
Chat purposes.
Sport servers.
Commercial Servers

7) What’s Globals in NodeJS? with instance

-> object equivalent to __filename, __dirname, setTimeout(), setInterval() and many others are some instance of World in nodejs. An object which exists in scope module, so we don’t have to incorporate these object in our software.

__filename instance:-

print the file title of present module

console.log(__filename);

/nodeJS-WorkSpace/project-1/index.js

__dirname instance:-

print the listing title of the present venture.

console.log(__dirname);

/nodeJS-WorkSpace/project-1

8) What are essentially the most generally used HTTP Request Strategies?

a very powerful and customary HTTP Request Strategies are GET,POST, PUT, DELETE are used to carry out CRUD (Create, Learn, Replace and Delete) operations in DataBase.

GET -> Request and retrieve information from server.

POST -> POST requests are make the most of to ship information to a server to create or replace or overwrite a useful resource.

frequent instance is once we add a photograph.

PUT -> once you need to modify a particular a part of useful resource, which is already a component of useful resource assortment.

PATCH -> PATCH technique provides a set of directions to switch the useful resource. PATCH is NOT idempotent.

DELETE -> as title says DELETE will delete useful resource from server.

9) What’s the MERN stack?

Stack is assortment of software program.

MongoDB -> NoSQL which stands for non relation database.

👉 https://www.mongodb.com/what-is-mongodb (official web site)

Specific.js -> The default net purposes framework.

👉 https://expressjs.com/ (official web site)

REACT.js -> React an open-source, entrance finish, JavaScript library for constructing consumer interfaces.

👉 https://reactjs.org/ (official web site)

Node.js -> nodejs is an open-source and cross-platform constructed on Chrome’s V8 engine constructed by Ryan Dahl for executing JavaScript code outdoors of the browser.

👉https://nodejs.org/en/ (official web site)

10) Are you able to console all HTTP standing code in NodeJS?

sure we are able to console all HTTP standing code.

first now we have to require a HTTP module from nodejs.

After that we are able to now use HTTP module inside our program.

Now now we have to kind following code

console.log(http.STATUS_CODES)

The above command will give following Object which look one thing like this

STATUS_CODES: {

‘100’: ‘Proceed’,

‘101’: ‘Switching Protocols’,

‘102’: ‘Processing’,

‘103’: ‘Early Hints’,

‘200’: ‘OK’,

‘201’: ‘Created’,

‘202’: ‘Accepted’,

‘203’: ‘Non-Authoritative Data’,

‘204’: ‘No Content material’,

‘205’: ‘Reset Content material’,

‘206’: ‘Partial Content material’,

‘207’: ‘Multi-Standing’,

‘208’: ‘Already Reported’,

‘226’: ‘IM Used’,

‘300’: ‘A number of Decisions’,

‘301’: ‘Moved Completely’,

‘302’: ‘Discovered’,

‘303’: ‘See Different’,

‘304’: ‘Not Modified’,

‘305’: ‘Use Proxy’,

‘307’: ‘Short-term Redirect’,

‘308’: ‘Everlasting Redirect’,

‘400’: ‘Dangerous Request’,

‘401’: ‘Unauthorized’,

‘402’: ‘Fee Required’,

‘403’: ‘Forbidden’,

‘404’: ‘Not Discovered’,

‘405’: ‘Technique Not Allowed’,

‘406’: ‘Not Acceptable’,

‘407’: ‘Proxy Authentication Required’,

‘408’: ‘Request Timeout’,

‘409’: ‘Battle’,

‘410’: ‘Gone’,

‘411’: ‘Size Required’,

‘412’: ‘Precondition Failed’,

‘413’: ‘Payload Too Giant’,

‘414’: ‘URI Too Lengthy’,

‘415’: ‘Unsupported Media Kind’,

‘416’: ‘Vary Not Satisfiable’,

‘417’: ‘Expectation Failed’,

‘418’: “I’m a Teapot”,

‘421’: ‘Misdirected Request’,

‘422’: ‘Unprocessable Entity’,

‘423’: ‘Locked’,

‘424’: ‘Failed Dependency’,

‘425’: ‘Too Early’,

‘426’: ‘Improve Required’,

‘428’: ‘Precondition Required’,

‘429’: ‘Too Many Requests’,

‘431’: ‘Request Header Fields Too Giant’,

‘451’: ‘Unavailable For Authorized Causes’,

‘500’: ‘Inner Server Error’,

‘501’: ‘Not Applied’,

‘502’: ‘Dangerous Gateway’,

‘503’: ‘Service Unavailable’,

‘504’: ‘Gateway Timeout’,

‘505’: ‘HTTP Model Not Supported’,

‘506’: ‘Variant Additionally Negotiates’,

‘507’: ‘Inadequate Storage’,

‘508’: ‘Loop Detected’,

‘509’: ‘Bandwidth Restrict Exceeded’,

‘510’: ‘Not Prolonged’,

‘511’: ‘Community Authentication Required’

}

11) What’s node js used for?

Once we are attempting to construct methods which has a excessive variety of request and response cycle. Like saving information to Knowledge Base, recordsdata entry.

Nodejs might be use in lots of software like.

The back-end for Social Media Networking
Single-page Software
Chat Software
Knowledge Streaming
IoT Software
Video Streaming

13) What’s npm in node js?

npm is that the default bundle supervisor for the JavaScript runtime environment Node.js. It consists of a press release shopper, moreover known as npm, and web data of public and paid-for private packages, known as the npm written document. The written document is accessed through the buyer, and likewise the accessible packages will probably be browsed and searched through the npm web site. The bundle supervisor and likewise the written document space unit managed by npm, Inc

It really works as an online repository for node.js packages/modules which might be discovered on https://www.npmjs.com/.
It really works as a Command-line utility to put in packages bundles.

14) Why node js is in style??

NodeJS is in style for a lot of causes equivalent to:-

-> NodeJS is quicker examine to different back-end languages.

-> Excessive Efficiency.

-> JavaScript In all places.

-> Simple to Modify and Keep.

-> Simple to take care of.

15) The way to set up npm in nodejs?

whereas putting in nodejs in your computer npm comes with it. so we don’t should obtain one other setup and set up it.
You possibly can test the npm model by typing npm -v on terminal/Command Immediate.

16) What’s MORGAN in node js

effectively there are numerous HTTP request logger center ware for Node.js like

-> Node-Loggly

-> Bunyan

-> Winston

however the preferred one is Morgan

Morgan is a utility instrument which helps us to console or log HTTP request from request-response cycle.

17) The way to set up node js

Step 1: go to this web site

→ https://nodejs.org/en/download/

Step 2: After that, you will note a number of working system choices select no matter working system you might be operating. In case you are operating home windows then click on on home windows Installer or if you’re operating macOS then click on on macOS Installer or if you’re operating Linux then click on on supply code.
Step 3: for checking nodejs is efficiently set up or not you possibly can go to cmd line or terminal in mac, then kind node -v for checking node model.

18) The way to set up node js in home windows

step 1: go to https://nodejs.org/en/.

Step 2: now obtain newest LTS model which stands for Lengthy Time period Help.

Step 3: after finishing obtain double click on on installer and set up the software program by accepting all phrases and situation.

Step 4: After accepting all phrases and circumstances click on on set up, set up will take hardly 2-5 min relying in your system configuration.

Step 5: for checking nodejs is efficiently set up or not you possibly can go to cmd line or terminal in mac, then kind node -v for checking node model.

19) The way to set up specific in node js?

Specific is among the hottest net framework for node.

Step 1: earlier than putting in specific now we have to initialize folder with command npm init.

Step 2: press enter for filling default worth in it.

Step 3: now kind npm i specific for putting in specific.

Step 4: for utilizing npm in your venture rgb(247, 247, 247)

20) The way to run node js server?

Step 1: for operating nodejs server we require specific and port on which our net server will run is that this it’s port 8001.

Step 2: setting specific to get (get request) from our server which your native host.

Step 3: with the assistance of app.pay attention we’re itemizing on port 8001.

Step 4: now kind node and title of file you need ot run in my case it’s index.js so kind

> node index.js

step 5: As we are able to see we’re efficiently in a position to render your web site.

21) The way to run file from node command immediate??

open your command immediate if you’re in home windows or terminal if you’re in mac/Linux after which kind node -v.

22) What’s specific in node Js??

Specific is among the hottest net framework for node. It have 16,631,385 Weekly downloads on npm with a really small measurement unpacked measurement is about 209KB.

Specific assist us to construct your web site sooner sturdy and straightforward to take care of code.

23) the right way to open node js command immediate

earlier than opening nodejs command immediate set up nodejs and NPM.

Step 1: set up nodejs from https://nodejs.org/en/ .

Step 2: run the installer and go away each factor to default and settle for time period and situation.

Step 3: write code on js file.

step 4: run JS file through the use of command node and title of file.

24) The way to render HTML utilizing node js?

Step 1: require specific module and outline port no. In my case its 8001.

Step 2: set a get request on ‘/’ route for sending a get request we use res.ship technique to ship content material to web site.

Step 3: in my case I need to despatched a HTML tag and render that tag, so we use <h1> MyGreatLearnig </h1> HTML tag and put inside the res.ship() technique.

Step 4: now now we have to pay attention the request(req) and response(res) to the request on port.

step 5: As we are able to see we’re efficiently in a position to render your web site.

25) Your favorite Nodejs framework and why?

Mongoose

Mongoose gives a straight-forward and schema-based resolution to mannequin and handle your database and designed to work in an asynchronous surroundings and helps each guarantees and callbacks which good appropriate with NodeJS.
It has 1,226,217 weekly downloads.

Specific.js

Expressjs is an online body Work construct on high of nodejs.
Expressjs deal with completely different HTTP requests (req) equivalent to fundamental routing, middleware, template engine and static recordsdata serving.
It has Weekly Downloads of 16,623,215.

Pug

PUG is template engine which in-built high of JS that’s utilized within the Node. js scheme. It’s a library that render HTML our bodies.
It has Weekly Downloads 1,163,220

Chalk

A easy string styling carried out on terminal. It assist us builders to distinguish between completely different kind of output on terminal.
It has Weekly Downloads 84,131,453.

Morgan

because the title says it generate large quantity of pretend information for testing your software.
It has Weekly Downloads 2,783,928.

faker.js

one essentially the most helpful dev utility for logging HTTP request on the console. It has Weekly Downloads of two,095,542.

26) Can your write a easy instance of an Asynchronous operate in nodejs?

A traditional operate might be written as an async operate by including a key phrase async on entrance of the operate.

27) What’s the LTS releases of Node.js?

An LTS stands for (Lengthy Time period Help) are supported for at the least 18 months and receives all bug repair, stability, safety patch efficiency. Additionally, they’re backwards appropriate.

The place as non LTS have some minor bug which may break your software.

28) What’s Callbacks?

A operate is handed into one other operate as an argument is known as callback operate.

29) What’s the distinction between Asynchronous and Non-blocking

The design of asynchronous explains that the message despatched gained’t present the reply on instant foundation a bit like we are inclined to ship the mail nevertheless don’t get the reply on an instantaneous foundation. It doesn’t have any dependency or order. thus up the system efficiency and efficiency. The server shops the information and as soon as the motion is accomplished it’ll be notified.

Non-blocking now responses with regardless of data obtainable. Furthermore, it doesn’t block any execution and retains on operating as per the requests. If an answer couldn’t be retrieved then in these circumstances API returns now with a blunder. Non-blocking is often used with I/O(enter/output). Node.js is itself supported by a non-blocking I/O mannequin. There are unit few ways in which of communication {that a} non-blocking I/O has accomplished. The asking operation is to be identified as soon as the operation is accomplished. Non-blocking resolution makes use of the help of JavaScript that gives an asking.

30) What does the runtime surroundings imply in Node.js?

The Node.js runtime is that the code stack answerable for operating your code on the respective platform and operating your service on the server.

31) What are Guarantees in Node.js?

it permits to affiliate handlers to AN asynchronous motion’s final success worth or failure motive. This lets asynchronous methods come again costs like synchronous strategies: slightly than the final word worth, the asynchronous approach returns a promise for the price at some goal throughout the future.

32) What’s a stub?

Stubbing and verification for node.js exams. allows you to validate and override habits of nested gadgets of code like strategies, require() and npm modules or possibly cases of classes. This library is galvanized on node-gently, MockJS and mock-require.

Function:

Produces simple, lightweight Objects able to extending down their tree
Stubs give canned solutions to carry out calls created all through test circumstances. Additionally, you’ll assert on with what these stubs have been referred to a
Successfully extendable straight forwardly or by an ExtensionManager.

33) What’s REPL?

REPL (READ, EVAL, PRINT, LOOP) might be a system surroundings nearly like Shell in (Unix/Linux) and cmd/terminal. NodeJS comes with the REPL setting as soon as it’s put in. The system interacts with the consumer by outputs of instructions/expressions used. it’s useful in writing and debugging the codes.

34) The way to join mongodb with node js?

Step 1: require mongoose bundle for monodb.

Step 2: kind password on the place of <PASSWORD> and Retailer it on const DB.

Step 3: move an object technique on the place useNewUrlParser set to true.

Step 4: move an object technique on the place useCreateIndex set to true,

Step 5: move an object technique on the place useFindAndModify set to true,

Step 6: move an object technique on the place useUnifiedTopology set to true,

{

useNewUrlParser: true,

useCreateIndex: true,

useFindAndModify: false,

useUnifiedTopology: true,

}

35) the right way to set up node js in Linux?

Step 1: open your terminal.

Step 2: kind sudo apt set up nodejs in your terminal and hit enter.

Step 3: for putting in npm.

Step 4: kind sudo apt set up npm in your terminal and hit enter.

36) What are the sorts of API capabilities in Node.js?

Their are 2 sorts of API capabilities accessible in Node.js:-

non-blocking capabilities, Asynchronous.
blocking capabilities, Synchronous,

37) Can I run nodejs on home windows?

Sure – it does.

You possibly can Obtain the nodejs installer on your respective Working System

from 👉 https://nodejs.org/download/

38) how will you use exterior libraries in node.js?

Suppose we need to use a library referred to as specific :-

Set up that library utilizing npm command npm set up specific.
After putting in library require it utilizing const specific = require(“specific”);
The library is able to use in your venture.

39) Does the fs module gives each syncs in addition to async strategies ??

sure fs module gives each sync in addition to async strategies.

40) What’s __dirname variable?

__dirname variable print the working listing.

41) Are you able to clarify the blocking code?

If the appliance has obtained to wait for some I/O operation in order to finish its execution any longer then the code liable for ready is regarded as blocking code.

42) What’s the Occasion loop in Node.js work? And How does it work?

By default, JavaScript is a single-threaded language for fixing this behaviour JavaScript distributing the duty to the respective system kernel, as a result of many of the fashionable kernel assist multi-threading these days which suggests the kernel can run the duty within the background with out blocking the present execution stack this gap phenomena referred to as occasion loop as a result of nodejs is constructed on the highest of nodejs, nodejs can also be a single-threaded however with the assistance of kernel Node.js to carry out non-blocking I/O operations.

43) What are the important thing options of Node.js?

Main key options of NodeJS are:

Asynchronous event-driven IO helps concurrent request dealing with –> All APIs of NodeJS is asynchronous in nature. This function means if a Node receives asking for some Enter/Output activity, it’ll execute that function throughout the background and proceed with the method of different requests. so it’ll not look ahead to the response from the earlier requests.

Code execution –>Code execution is way sooner on Node.js, Nodejs makes use of the V8 engine which is open-source and maintained by google additionally powers Google Chrome net browser.

Single-Threaded however Extremely scalable –> Node.js makes use of a single thread mannequin for the occasion course of. The response from these occasions may or may not attain the server directly. Nonetheless, this doesn’t block completely different operations. subsequently creating Node.js extraordinarily scalable. The response from these events was servers produce restricted threads to deal with requests whereas Node.js creates one thread that has service to considerable bigger numbers of such requests.

Node.js library makes use of JavaScript – That is one other vital a part of Node.js from the engineer’s perspective. Most designers are as of now educated in JavaScript. Subsequently, enchancment in Node.js will get easier for an engineer who is aware of JavaScript.

44) Which IDEs or code Editor you like for Node.js improvement? And why

Private I take advantage of visible studio code as a result of it’s free open-source and builders of visible studio code all the time giving patches for safety and efficiency replace as effectively.
Speaking about IDEs I typically desire net storm which is developed by Jet Brains.
And particularly centered on net improvement so it has all the required instruments for constructing a web site or an online software.

45) Give a real-world instance of the working mechanism of NodeJS?

I’m taking an instance of a deliveryman

Normally, the deliveryman goes to each and each home to ship the packet. Node.js works throughout the identical technique and processes one request at a time. the matter arises as soon as anyone’s dwelling shouldn’t be open. The supply man can’t cease at one home and wait till it will get displayed. What he can do subsequent, is to resolution the proprietor and lift him to the choice as soon as the house is open. In the meantime, he’s attending to various locations for supply. Node.js works throughout the identical technique. It doesn’t look ahead to the method of the request to finish (the home is open). As an alternative, it attaches a recall operation (name from the proprietor of the home) to that. Each time the method of the a call for participation completes (the house is open), a occurring will get often known as that triggers the related recall operates to ship the response.

46) Is Node.js completely based mostly on a single-thread or not?

Sure it true that nodejs is predicated on single-thread.

47) What’s bundle.json?

bundle.json is one a very powerful file for engaged on nodejs. It’s plain JSON file the place venture frequent data and meta information saves.

Which look one thing like this

{
  "title": "venture Title",
  "model": "1.0.0",
  "description": "TODO",
  "major": "index.js",
  "scripts": {
    "begin": "node index.js"
  },
  "creator": "title of creator",
  "license": "ISC",
  "dependencies": {
    "specific": "^4.17.1"
  }
}

48) The way to get a distant Handle in node js?

By utilizing req operate we are able to get consumer’s IP deal with in node js.

Code -> req.connection.remoteAddress

49) What’s DOM?

Dom stands for doc object mannequin.

50) Is there’s various to question Selector?

sure it’s doc.getElementBy

51) What are the three main sorts of database that are in style in business?

1) relational -> These information-based are categorized by a group of tables wherever information get work right into a per-defined class. The desk consists of rows affiliate levels columns wherever the column has an entry for data for a specific class and rows incorporates occasion for that data outlined in line with the category. The Structured search language (SQL) is that the commonplace consumer and laptop program interface for an digital data service.

Instance MySQL, PostgreSQL, Oracle Database

2) No SQL database (non relational Database) -> These are used for enormous units of distributed data. Some large data efficiency issues are successfully dealt with by relative databases, such quiet issues are merely managed by No SQL databases. They’re have been economical in analyzing giant-size unstructured data which will probably be held on a number of digital servers of the cloud.

Instance MongoDB

3) Graph -> The graph might be an assortment of nodes and edges wherever each node is employed to characterize an entity and each edge describes the connection between entities. Graph-oriented data, or graph data, might be a type of No SQL data that makes use of graph idea to retailer, map, and query relationships.

52) are you able to checklist a few of the hottest JavaScript libraries and frameworks?

ReactJS -> Created by Fb, the React framework may be very in style these days and it wont to develop and function the dynamic interface of the net pages with excessive incoming visitors. It makes the utilization of a digital DOM, and therefore, the blending of an equal with any software is moreover straightforward.

Meteor -> Meteor’s software house (aka Meteor.js or MeteorJS) serves the title itself because it’s diversified as a result of it covers nearly the numerous parts of the code improvement. The makes use of of this framework embrace very important areas like back-end improvement, administration of the data, enterprise logic, and rendering of the front-end.

These Node.js interview questions would provide help to perceive what sort of questions could are available in an interview, undergo these Node.js interview questions, and crack your subsequent interview in a single go.

All The Greatest on your Interview

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