Top 50+Nodejs Interview Question and Answer 2024

Suggestions earlier than you attend Node.JS an interview

Put together for frequent interview questions which we’re going to discuss on this weblog. Earlier than you try any interview be sure to ought to analysis the corporate’s background, it should assist communication between you and the interviewee.Be certain that your GitHub repository has a venture and an open-source contribution on it, an empty repository is an indication of a nasty developer.Be certain that your LinkedIn profile is nicely maintained too.Present your Management abilities. Follow your answering abilities with another person or in entrance of a mirrorThink about your Strengths as a result of these are FAQsMention a particular accomplishment or exercise that matches the obligation.Give legit, simple solutions.Carry a replica of your resume for every assembly.Be certain that are updated with present information.

Node.js is a widespread server-side platform utilized by many firms. If you’re 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 just a few generally requested Node.js interview questions that you simply would possibly concentrate on, we additionally advocate you to give attention to unique Node.js interview questions.

We’ve got compiled a listing of Node.js interview questions that come up usually in interviews and likewise assist you 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 may solely entry your net web page however once you enable 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 techniques core module.

usually, we use to construct back-end companies or API additionally referred to as (utility programming interfaces) these are the companies that energy our shopper functions like an internet app operating within an internet browser or a cell utility.

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

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

2) What are the info varieties in Node.js? Primitive Sorts.

Nodejs is constructed on prime of JavaScript so a lot of the information sort that current in JavaScript can also be current in Nodejs.

String -> It comprise set of characters that may additionally comprise 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 sort.

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 extra information sort which isn’t accessible within the browser’s JavaScript

Buffer →  Buffer is especially 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 are you going to forestall 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 on the market for JavaScript.

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

command -> npm set up async

Utilizing Guarantees

Guarantees provide an affiliate an alternate method 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 return. It takes 2 nonobligatory arguments, every operate. wanting on the state of the promise simply considered one 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 not entry DOM(doc object mannequin) in node.  

6) When Ought to We Use Node.Js?

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

For instance :

IoT ApplicationsVideo Streaming.Chat functions.Sport servers.Commercial Servers

7)  What’s Globals in NodeJS? with instance

->  object similar to __filename, __dirname, setTimeout(), setInterval() and so forth 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 utility.

    __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 probably the most generally used HTTP Request Strategies?

crucial 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 methodology provides a set of directions to change 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)

Categorical.js -> The default net functions framework.

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

REACT.js -> React an open-source, entrance finish, JavaScript library for constructing person       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 we’ve got to require a HTTP module from nodejs.

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

Now we’ve got to sort 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 Info’,

    ‘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 Selections’,

    ‘301’: ‘Moved Completely’,

    ‘302’: ‘Discovered’,

    ‘303’: ‘See Different’,

    ‘304’: ‘Not Modified’,

    ‘305’: ‘Use Proxy’,

    ‘307’: ‘Non permanent Redirect’,

    ‘308’: ‘Everlasting Redirect’,

    ‘400’: ‘Unhealthy Request’,

    ‘401’: ‘Unauthorized’,

    ‘402’: ‘Cost Required’,

    ‘403’: ‘Forbidden’,

    ‘404’: ‘Not Discovered’,

    ‘405’: ‘Methodology 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 Sort’,

    ‘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’: ‘Inside Server Error’,

    ‘501’: ‘Not Carried out’,

    ‘502’: ‘Unhealthy 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?

After we try to construct techniques 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 utility like.

The back-end for Social Media NetworkingSingle-page ApplicationChat ApplicationData StreamingIoT ApplicationVideo Streaming

13) What’s npm in node js?

npm is that the default package deal supervisor for the JavaScript runtime ambiance Node.js. It consists of a press release shopper, moreover known as npm, and web info of public and paid-for private packages, known as the npm written document. The written document is accessed by way of the patron, and likewise the accessible packages can be browsed and searched by way of the npm web site. The package deal supervisor and likewise the written document space unit managed by npm, Inc

It really works as an internet 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 widespread??

NodeJS is widespread for a lot of causes similar to:-

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

-> Excessive Efficiency.

-> JavaScript In every single place.

-> Simple to Modify and Preserve.

-> Simple to take care of.

15) The best way to set up npm in nodejs?

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

16) What’s MORGAN in node js

nicely 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 device which helps us to console or log HTTP request from request-response cycle.

17) The best way to set up node js

Step 1: go to this web site 

→ https://nodejs.org/en/obtain/

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

18)  The best 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’ll be able to go to cmd line or terminal in mac, then sort node -v for checking node model.

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

     Categorical is among the hottest net framework for node. 

Step 1: earlier than putting in specific we’ve got to initialize folder with command npm init.

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

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

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

20) The best 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.hear we’re itemizing on port 8001.

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

  > node index.js

step 5: As we are able to see we’re efficiently capable of render your web site.

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

open your command immediate in case you are in home windows or terminal in case you are in mac/Linux after which sort node -v.

22) What’s specific in node Js??

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

Categorical assist us to construct your web site quicker sturdy and straightforward to take care of code.

23) easy methods 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 by utilizing command node and title of file.

24) The best 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 methodology 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 within the res.ship() methodology.

Step 4: now we’ve got to hear the request(req) and response(res) to the request on port. 

step 5: As we are able to see we’re efficiently capable of 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 suitable with NodeJS.It has 1,226,217 weekly downloads.

Categorical.js

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

Pug

PUG is template engine which inbuilt prime 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 accomplished on terminal. It assist us builders to distinguish between completely different sort of output on terminal.It has Weekly Downloads 84,131,453.

Morgan

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

faker.js

one probably 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 standard 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 suitable.

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

28) What’s Callbacks?

 A operate is handed into one other operate as an argument is named 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 rapid foundation a bit like we are likely to ship the mail nonetheless 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 info and as soon as the motion is accomplished it’ll be notified.

Non-blocking now responses with irrespective of info 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 cause. This lets asynchronous methods come again costs like synchronous strategies: relatively than the final word worth, the asynchronous method returns a promise for the price at some function inside the future.

32) What’s a stub?

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

Characteristic:

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

33)  What’s REPL?

REPL (READ, EVAL, PRINT, LOOP) could possibly be a system surroundings virtually 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 person by outputs of instructions/expressions used. it’s useful in writing and debugging the codes.

34) The best way to join mongodb with node js?

Step 1: require mongoose package deal for monodb.

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

Step 3: cross an object methodology on the place useNewUrlParser set to true.

Step 4: cross an object methodology on the place useCreateIndex set to true,

Step 5: cross an object methodology on the place useFindAndModify set to true,

Step 6: cross an object methodology on the place useUnifiedTopology set to true,

{

    useNewUrlParser: true,

    useCreateIndex: true,

    useFindAndModify: false,

    useUnifiedTopology: true,

  }

35) easy methods to set up node js in Linux?

Step 1: open your terminal.

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

Step 3: for putting in npm.

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

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

Their are 2 forms 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 may Obtain the nodejs installer on your respective Working System 

from 👉 https://nodejs.org/obtain/ 

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 applying has acquired to watch for some I/O operation in order to finish its execution any longer then the code liable for ready is considered 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 a lot of the trendy kernel help multi-threading these days which implies 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 job, it’ll execute that function inside the background and proceed with the method of other requests. so it’ll not look ahead to the response from the earlier requests.

Code execution –>Code execution is far quicker 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 ample 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 less complicated for an engineer who is aware of JavaScript.

44) Which IDEs or code Editor you like for Node.js growth? 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 nicely.Speaking about IDEs I usually favor net storm which is developed by Jet Brains.And particularly centered on net growth so it has all the mandatory instruments for constructing an internet site or an internet utility.

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 inside the identical methodology and processes one request at a time. the matter arises as soon as anyone’s dwelling is just not 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 inside the identical methodology. It doesn’t look ahead to the method of the request to finish (the home is open). As a substitute, it attaches a recall operation (name from the proprietor of the home) to that. Every 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 fully primarily based on a single-thread or not?

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

47) What’s package deal.json?

package deal.json is one crucial file for engaged on nodejs. It’s plain JSON file the place venture frequent info and meta information saves. 

Which look one thing like this

{
“title”: “venture Identify”,
“model”: “1.0.0”,
“description”: “TODO”,
“important”: “index.js”,
“scripts”: {
“begin”: “node index.js”
},
“writer”: “title of writer”,
“license”: “ISC”,
“dependencies”: {
“specific”: “^4.17.1”
}
}

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

By utilizing req operate we are able to get person’s IP handle 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 forms of database that are widespread in trade?

1)  relational -> These information-based are categorised 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 info for a specific class and rows comprises occasion for that info outlined in step with the category. The Structured search language (SQL) is that the commonplace person and laptop program interface for an digital info service.

Instance  MySQL, PostgreSQL, Oracle Database

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

Instance MongoDB

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

52) are you able to record a number of the hottest JavaScript libraries and frameworks?

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

Meteor -> Meteor’s utility area (aka Meteor.js or MeteorJS) serves the title itself because it’s assorted as a result of it covers just about the various parts of the code growth. The makes use of of this framework embrace important areas like back-end growth, administration of the data, enterprise logic, and rendering of the front-end.

These Node.js interview questions would assist you 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