Tips before you attend Node.JS an interview
- Prepare for common interview questions which we are going to talk about in this blog.
- Before you attempt any interview make sure you should research the company’s background, it will help communication between you and the interviewee.
- Make sure your GitHub repository has a project and an open-source contribution on it, an empty repository is a sign of a bad developer.
- Make sure your LinkedIn profile is well maintained too.
- Show your Leadership skills.
- Practice your answering skills with someone else or in front of a mirror
- Think about your Strengths because these are FAQs
- Mention a specific accomplishment or activity that matches the duty.
- Give legit, straightforward answers.
- Carry a duplicate of your resume for each meeting.
- Make sure are up to date with current info.
Node.js is a popular server-side platform used by many companies. If you are preparing for a career change, it’s always a good idea to brush up on your interview skills beforehand. Although there are a few commonly asked Node.js interview questions that you might be aware of, we also recommend you to focus on exclusive Node.js interview questions.
We have compiled a list of Node.js interview questions that come up often in interviews and also help you understand the fundamental concepts of Node.js.
Beginner’s NodeJS interview questions
1) What is nodeJS
NodeJS or node is an open-source and cross-platform runtime environment that is built on Chrome’s V8 engine (which is written in c++) for executing JavaScript code outside of the browser.
JavaScript runs in the browser it can only access your web page but when you allow it to run on your machine with NodeJS we just created a whole new world where js can access the file system, Events, OS, and other systems core module.
generally, we use to build back-end services or API also called (application programming interfaces) these are the services that power our client applications like a web app running inside of a web browser or a mobile application.
Companies like’s Netflix, LinkedIn, Uber, and many more uses nodeJS js for managing their services.
So today javaScript is also a back-end as well as the front-end programming language.
2) What are the data types in Node.js? Primitive Types.
Nodejs is built on top of JavaScript so most of the data type that present in JavaScript is also present in Nodejs.
String -> It contain set of characters that can also contain spaces and numbers for example
const string1 = “A string primitive”;
const string2 = ‘i am string too’;
const string3 = `number like 1,2,3 are also a example of string`;
Number → by default every value is float data type.
const num = 2;
Boolean → true or false.
const num = true;
const num2 = false;
Undefined → value if not assigned to the variable.
const num; // num is undefined.
Null → absence of object value.
nodejs has one more additional data type which is not available in the browser’s JavaScript
Buffer → Buffer is mainly used to store binary data.
3) What is callback hell in Node.js?
Callback hell is an event when a developer tries to execute multiple asynchronous operations one after the other.
aync_Callback1(function () {
aync_Callback2(function () {
aync_Callback3(function () {
aync_Callback4(function () {
})
})
})
4) How can you prevent CallBack hell?
Techniques for avoiding callback hell
Using Async.js
is a very popular utility module for handling Asynchronous callbacks.
Also, this utility module is available for JavaScript.
Async.js -> https://www.npmjs.com/package/async
command -> npm install async
Using Promises
Promises offer an associate an alternate way to write async code. They either come the results of execution or the error/exception. Implementing guarantees needs the utilization of <.then()> perform that waits for the promise object to come. It takes 2 nonobligatory arguments, each function. looking at the state of the promise just one of them can get referred to as. the primary call payoff if the promise gets consummated. However, if the promise gets rejected, then the second performance can get referred to as.
5) Can you access DOM in the node?
No, you cannot access DOM(document object model) in node.
6) When Should We Use Node.Js?
-> NodeJS is generally used when we are building systems that require a high number of I/O operations. Like saving data to DataBase, files access.
For example :
- IoT Applications
- Video Streaming.
- Chat applications.
- Game servers.
- Advertisement Servers
7) What is Globals in NodeJS? with example
-> object such as __filename, __dirname, setTimeout(), setInterval() etc are some example of Global in nodejs. An object which exists in scope module, so we don’t have to include these object in our application.
__filename example:-
print the file name of current module
console.log(__filename);
/nodeJS-WorkSpace/project-1/index.js
__dirname example:-
print the directory name of the current project.
console.log(__dirname);
/nodeJS-WorkSpace/project-1
8) What are the most commonly used HTTP Request Methods?
the most important and common HTTP Request Methods are GET,POST, PUT, DELETE are used to perform CRUD (Create, Read, Update and Delete) operations in DataBase.
GET -> Request and retrieve data from server.
POST -> POST requests are utilize to send data to a server to create or update or overwrite a resource.
common example is when we upload a photo.
PUT -> when you want to modify a specific part of resource, which is already a part of resource collection.
PATCH -> PATCH method supplies a set of instructions to modify the resource. PATCH is NOT idempotent.
DELETE -> as name says DELETE will delete resource from server.
9) What is the MERN stack?
Stack is collection of software.
MongoDB -> NoSQL which stands for non relation database.
👉 https://www.mongodb.com/what-is-mongodb (official website)
Express.js -> The default web applications framework.
👉 https://expressjs.com/ (official website)
REACT.js -> React an open-source, front end, JavaScript library for building user interfaces.
👉 https://reactjs.org/ (official website)
Node.js -> nodejs is an open-source and cross-platform built on Chrome’s V8 engine built by Ryan Dahl for executing JavaScript code outside of the browser.
👉https://nodejs.org/en/ (official website)
10) Can you console all HTTP status code in NodeJS?
yes we can console all HTTP status code.
first we have to require a HTTP module from nodejs.
After that we can now use HTTP module inside of our program.
Now we have to type following code
console.log(http.STATUS_CODES) 
The above command will give following Object which look something like this
STATUS_CODES: {
‘100’: ‘Continue’,
‘101’: ‘Switching Protocols’,
‘102’: ‘Processing’,
‘103’: ‘Early Hints’,
‘200’: ‘OK’,
‘201’: ‘Created’,
‘202’: ‘Accepted’,
‘203’: ‘Non-Authoritative Information’,
‘204’: ‘No Content’,
‘205’: ‘Reset Content’,
‘206’: ‘Partial Content’,
‘207’: ‘Multi-Status’,
‘208’: ‘Already Reported’,
‘226’: ‘IM Used’,
‘300’: ‘Multiple Choices’,
‘301’: ‘Moved Permanently’,
‘302’: ‘Found’,
‘303’: ‘See Other’,
‘304’: ‘Not Modified’,
‘305’: ‘Use Proxy’,
‘307’: ‘Temporary Redirect’,
‘308’: ‘Permanent Redirect’,
‘400’: ‘Bad Request’,
‘401’: ‘Unauthorized’,
‘402’: ‘Payment Required’,
‘403’: ‘Forbidden’,
‘404’: ‘Not Found’,
‘405’: ‘Method Not Allowed’,
‘406’: ‘Not Acceptable’,
‘407’: ‘Proxy Authentication Required’,
‘408’: ‘Request Timeout’,
‘409’: ‘Conflict’,
‘410’: ‘Gone’,
‘411’: ‘Length Required’,
‘412’: ‘Precondition Failed’,
‘413’: ‘Payload Too Large’,
‘414’: ‘URI Too Long’,
‘415’: ‘Unsupported Media Type’,
‘416’: ‘Range 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’: ‘Upgrade Required’,
‘428’: ‘Precondition Required’,
‘429’: ‘Too Many Requests’,
‘431’: ‘Request Header Fields Too Large’,
‘451’: ‘Unavailable For Legal Reasons’,
‘500’: ‘Internal Server Error’,
‘501’: ‘Not Implemented’,
‘502’: ‘Bad Gateway’,
‘503’: ‘Service Unavailable’,
‘504’: ‘Gateway Timeout’,
‘505’: ‘HTTP Version Not Supported’,
‘506’: ‘Variant Also Negotiates’,
‘507’: ‘Insufficient Storage’,
‘508’: ‘Loop Detected’,
‘509’: ‘Bandwidth Limit Exceeded’,
‘510’: ‘Not Extended’,
‘511’: ‘Network Authentication Required’
}
11) What is node js used for?
When we are trying to build systems which has a high number of request and response cycle. Like saving data to Data Base, files access.
Nodejs can be use in many application like.
- The back-end for Social Media Networking
- Single-page Application
- Chat Application
- Data Streaming
- IoT Application
- Video Streaming
13) What is npm in node js?
npm is that the default package manager for the JavaScript runtime atmosphere Node.js. It consists of a statement consumer, additionally referred to as npm, and internet information of public and paid-for personal packages, referred to as the npm written record. The written record is accessed via the consumer, and also the accessible packages will be browsed and searched via the npm website. The package manager and also the written record area unit managed by npm, Inc
- It works as a web repository for node.js packages/modules which can be found on https://www.npmjs.com/.
- It works as a Command-line utility to install packages bundles.
14) Why node js is popular??
NodeJS is popular for many reasons such as:-
-> NodeJS is faster compare to other back-end languages.
-> High Performance.
-> JavaScript Everywhere.
-> Easy to Modify and Maintain.
-> Easy to maintain.
15) How to install npm in nodejs?
while installing nodejs on your pc npm comes with it. so we don’t have to download another setup and install it.
You can check the npm version by typing npm -v on terminal/Command Prompt.
16) What is MORGAN in node js
well there are many HTTP request logger middle ware for Node.js like
-> Node-Loggly
-> Bunyan
-> Winston
but the most popular one is Morgan
Morgan is a utility tool which helps us to console or log HTTP request from request-response cycle.
17) How to install node js
Step 1: go to this website
→ https://nodejs.org/en/download/
Step 2: After that, you will see multiple operating system options choose whatever operating system you are running. If you are running windows then click on windows Installer or if you are running macOS then click on macOS Installer or if you are running Linux then click on source code.
Step 3: for checking nodejs is successfully install or not you can go to cmd line or terminal in mac, then type node -v for checking node version.
18) How to install node js in windows
step 1: go to https://nodejs.org/en/.
Step 2: now download latest LTS version which stands for Long Term Support.
Step 3: after completing download double click on installer and install the software by accepting all terms and condition.
Step 4: After accepting all terms and conditions click on install, install will take hardly 2-5 min depending on your system configuration.
Step 5: for checking nodejs is successfully install or not you can go to cmd line or terminal in mac, then type node -v for checking node version.
19) How to install express in node js?
Express is one of the most popular web framework for node.
Step 1: before installing express we have to initialize folder with command npm init.
Step 2: press enter for filling default value in it.
Step 3: now type npm i express for installing express.
Step 4: for using npm in your project rgb(247, 247, 247)
20) How to run node js server?
Step 1: for running nodejs server we require express and port on which our web server will run is this it is port 8001.
Step 2: setting express to get (get request) from our server which your local host.
Step 3: with the help of app.listen we are listing on port 8001.
Step 4: now type node and name of file you want ot run in my case it is index.js so type
> node index.js
step 5: As we can see we are successfully able to render your website.
21) How to run file from node command prompt??
open your command prompt if you are in windows or terminal if you are in mac/Linux and then type node -v.
22) What is express in node Js??
Express is one of the most popular web framework for node. It have 16,631,385 Weekly downloads on npm with a very small size unpacked size is about 209KB.
Express help us to build your website faster robust and easy to maintain code.
23) how to open node js command prompt
before opening nodejs command prompt install nodejs and NPM.
Step 1: install nodejs from https://nodejs.org/en/ .
Step 2: run the installer and leave every thing to default and accept term and condition.
Step 3: write code on js file.
step 4: run JS file by using command node and name of file.
24) How to render HTML using node js?
Step 1: require express module and define port no. In my case its 8001.
Step 2: set a get request on ‘/’ route for sending a get request we use res.send method to send content to website.
Step 3: in my case I want to sent a HTML tag and render that tag, so we use <h1> MyGreatLearnig </h1> HTML tag and put inside of the res.send() method.
Step 4: now we have to listen the request(req) and response(res) to the request on port.
step 5: As we can see we are successfully able to render your website.
25) Your favourite Nodejs framework and why?
- Mongoose
- Mongoose provides a straight-forward and schema-based solution to model and manage your database and designed to work in an asynchronous environment and supports both promises and callbacks which perfect compatible with NodeJS.
- It has 1,226,217 weekly downloads.
- Express.js
- Expressjs is a web frame Work build on top of nodejs.
- Expressjs handle different HTTP requests (req) such as basic routing, middleware, template engine and static files serving.
- It has Weekly Downloads of 16,623,215.
- Pug
- PUG is template engine which built in top of JS that’s utilized in the Node. js scheme. It is a library that render HTML bodies.
- It has Weekly Downloads 1,163,220
- Chalk
- A simple string styling done on terminal. It help us developers to differentiate between different type of output on terminal.
- It has Weekly Downloads 84,131,453.
- Morgan
- as the name says it generate massive amount of fake data for testing your application.
- It has Weekly Downloads 2,783,928.
- faker.js
- one the most useful dev utility for logging HTTP request on the console. It has Weekly Downloads of 2,095,542.
26) Can your write a simple example of an Asynchronous function in nodejs?
A normal function can be written as an async function by adding a keyword async on front of the function.
27) What is the LTS releases of Node.js?
An LTS stands for (Long Term Support) are supported for at least 18 months and receives all bug fix, stability, security patch performance. Also, they are backwards compatible.
Where as non LTS have some minor bug which can break your application.
28) What is Callbacks?
A function is passed into another function as an argument is called callback function.
29) What is the difference between Asynchronous and Non-blocking
The design of asynchronous explains that the message sent won’t provide the reply on immediate basis a bit like we tend to send the mail however don’t get the reply on a right away basis. It doesn’t have any dependency or order. thus up the system potency and performance. The server stores the data and once the action is completed it’ll be notified.
Non-blocking now responses with no matter information obtainable. Moreover, it doesn’t block any execution and keeps on running as per the requests. If a solution couldn’t be retrieved then in those cases API returns now with a blunder. Non-blocking is usually used with I/O(input/output). Node.js is itself supported by a non-blocking I/O model. There are unit few ways that of communication that a non-blocking I/O has completed. The asking operation is to be known once the operation is completed. Non-blocking decision uses the assistance of JavaScript that provides an asking.
30) What does the runtime environment mean in Node.js?
The Node.js runtime is that the code stack responsible for running your code on the respective platform and running your service on the server.
31) What are Promises in Node.js?
it permits to associate handlers to AN asynchronous action’s ultimate success value or failure reason. This lets asynchronous ways come back prices like synchronous methods: rather than the ultimate value, the asynchronous technique returns a promise for the worth at some purpose within the future.
32) What is a stub?
Stubbing and verification for node.js tests. permits you to validate and override behavior of nested items of code like methods, require() and npm modules or maybe instances of categories. This library is galvanized on node-gently, MockJS and mock-require.
Feature:
- Produces straightforward, light-weight Objects capable of extending down their tree
- Stubs give canned answers to perform calls created throughout check cases. Also, you’ll assert on with what these stubs were referred to a
- Effectively extendable straight forwardly or through an ExtensionManager.
33) What is REPL?
REPL (READ, EVAL, PRINT, LOOP) could be a system environment almost like Shell in (Unix/Linux) and cmd/terminal. NodeJS comes with the REPL setting once it’s put in. The system interacts with the user through outputs of commands/expressions used. it’s helpful in writing and debugging the codes.
34) How to connect mongodb with node js?
Step 1: require mongoose package for monodb.
Step 2: type password on the place of <PASSWORD> and Store it on const DB.
Step 3: pass an object method on where useNewUrlParser set to true.
Step 4: pass an object method on where useCreateIndex set to true,
Step 5: pass an object method on where useFindAndModify set to true,
Step 6: pass an object method on where useUnifiedTopology set to true,
{
useNewUrlParser: true,
useCreateIndex: true,
useFindAndModify: false,
useUnifiedTopology: true,
}
35) how to install node js in Linux?
Step 1: open your terminal.
Step 2: type sudo apt install nodejs on your terminal and hit enter.
Step 3: for installing npm.
Step 4: type sudo apt install npm on your terminal and hit enter.
36) What are the types of API functions in Node.js?
Their are 2 types of API functions available in Node.js:-
- non-blocking functions, Asynchronous.
- blocking functions, Synchronous,
37) Can I run nodejs on windows?
Yes – it does.
You can Download the nodejs installer for your respective Operating System
from 👉 https://nodejs.org/download/
38) how can you use external libraries in node.js?
Suppose we want to use a library called express :-
- Install that library using npm command npm install express.
- After installing library require it using const express = require(“express”);
- The library is ready to use in your project.
39) Does the fs module provides both syncs as well as async methods ??
yes fs module provides both sync as well as async methods.
40) What is __dirname variable?
__dirname variable print the working directory.
41) Can you explain the blocking code?
If the application has got to stay up for some I/O operation so as to complete its execution any longer then the code chargeable for waiting is thought of as blocking code.
42) What is the Event 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 task to the respective system kernel, because most of the modern kernel support multi-threading nowadays which means the kernel can run the task in the background without blocking the current execution stack this hole phenomena called event loop because nodejs is built on the top of nodejs, nodejs is also a single-threaded but with the help of kernel Node.js to perform non-blocking I/O operations.
43) What are the key features of Node.js?
Major key features of NodeJS are:
Asynchronous event-driven IO helps concurrent request handling –> All APIs of NodeJS is asynchronous in nature. This feature means if a Node receives asking for some Input/Output task, it’ll execute that operate within the background and continue with the process of alternative requests. so it’ll not watch for the response from the previous requests.
Code execution –>Code execution is much faster on Node.js, Nodejs uses the V8 engine which is open-source and maintained by google also powers Google Chrome web browser.
Single-Threaded but Highly scalable –> Node.js uses a single thread model for the event process. The response from these events could or might not reach the server at once. However, this doesn’t block different operations. therefore creating Node.js extremely scalable. The reaction from these occasions was servers produce restricted threads to handle requests whereas Node.js creates one thread that has service to abundant larger numbers of such requests.
Node.js library uses JavaScript – This is another significant part of Node.js from the engineer’s perspective. Most designers are as of now knowledgeable in JavaScript. Subsequently, improvement in Node.js gets simpler for an engineer who knows JavaScript.
44) Which IDEs or code Editor you prefer for Node.js development? And why
Personal I use visual studio code because it’s free open-source and developers of visual studio code always giving patches for security and performance update as well.
Talking about IDEs I generally prefer web storm which is developed by Jet Brains.
And especially focused on web development so it has all the necessary tools for building a website or a web application.
45) Give a real-world example of the working mechanism of NodeJS?
I am taking an example of a deliveryman
Usually, the deliveryman goes to every and every house to deliver the packet. Node.js works within the same method and processes one request at a time. the matter arises once anybody’s home is not open. The delivery man can’t stop at one house and wait until it gets displayed. What he can do next, is to decision the owner and raise him to the decision once the home is open. Meanwhile, he’s getting to alternative places for delivery. Node.js works within the same method. It doesn’t watch for the process of the request to complete (the house is open). Instead, it attaches a recall operation (call from the owner of the house) to that. Whenever the process of the letter of invitation completes (the home is open), a happening gets known as that triggers the associated recall operates to send the response.
46) Is Node.js entirely based on a single-thread or not?
Yes it true that nodejs is based on single-thread.
47) What is package.json?
package.json is one the most important file for working on nodejs. It is plain JSON file where project common information and meta data saves.
Which look something like this
{
"name": "project Name",
"version": "1.0.0",
"description": "TODO",
"main": "index.js",
"scripts": {
"start": "node index.js"
},
"author": "name of author",
"license": "ISC",
"dependencies": {
"express": "^4.17.1"
}
}
48) How to get a remote Address in node js?
By using req function we can get user’s IP address in node js.
Code -> req.connection.remoteAddress
49) What is DOM?
Dom stands for document object model.
50) Is there is alternative to query Selector?
yes it’s document.getElementBy
51) What are the 3 major types of database which are popular in industry?
1) relational -> These information-based are classified by a collection of tables wherever data get work into a per-defined class. The table consists of rows associate degrees columns wherever the column has an entry for information for a selected class and rows contains instance for that information outlined in keeping with the class. The Structured search language (SQL) is that the commonplace user and computer program interface for an electronic information service.
Example MySQL, PostgreSQL, Oracle Database
2) No SQL database (non relational Database) -> These are used for huge sets of distributed information. Some massive information performance problems are effectively handled by relative databases, such quiet problems are simply managed by No SQL databases. They are were economical in analyzing giant-size unstructured information which will be held on multiple virtual servers of the cloud.
Example MongoDB
3) Graph -> The graph could be an assortment of nodes and edges wherever every node is employed to represent an entity and every edge describes the connection between entities. Graph-oriented info, or graph info, could be a form of No SQL info that uses graph theory to store, map, and question relationships.
52) can you list some of the most popular JavaScript libraries and frameworks?
ReactJS -> Created by Facebook, the React framework is very popular nowadays and it wont to develop and operate the dynamic interface of the online pages with high incoming traffic. It makes the utilization of a virtual DOM, and hence, the mixing of an equivalent with any application is additionally easy.
Meteor -> Meteor’s application space (aka Meteor.js or MeteorJS) serves the name itself since it’s varied because it covers virtually the many portions of the code development. The uses of this framework embrace vital areas like back-end development, management of the information, business logic, and rendering of the front-end.
These Node.js interview questions would help you understand what kind of questions may come in an interview, go through these Node.js interview questions, and crack your next interview in one go.
All The Best for your Interview
