Top 100 JavaScript Interview Questions and Answers

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JavaScript Interview Masterclass: Top 200 Questions & Answer
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All the best for your interviews.

[@aniketshahane7448]

For my reference : 12:39 Chapter 2 : Variables & Datatypes 28:12 Chapter 3 : Operators & Conditions 46:16 Chapter 4 : Arrays 1:11:39 Chapter 5 : Loops 1:26:25 Chapter 6 : Functions 1:56:01 Chapter 7 : Strings 2:01:55 Chapter 8 : DOM 2:18:22 Chapter 9 : Error Handling 2:25:57 Chapter 10 : Objects 2:45:28 Chapter 11 : Events

[@ahmed_raaphat]

🇵🇸 TIMESTAMPS: 🇵🇸 02:14 what is Javascript? what is the role of JS engine? 05:00 What are Client side and Server side? 06:30 What is Scope in JS? 09:48 What is Hoisting in Javascript? 11:49 What is JSON? 13:18 What are variables? var vs let vs const. 16:50 What are data types in JS? 18:15 what is the difference between primitive and non-primitive data types? 22:23 what is the difference between null and undefined in JS? 25:12 what is the use of typeof operator? 26:28 what is type coercion in JS? 28:43 what is operator precedence? 29:37 Unary vs Binary vs Ternary operators. 31:10 What is short-circuit evaluation in JS? 34:22 Conditional Statement Types. 41:01 Double equals == vs === Triple equals 42:49 Spread operator and Rest operator in JS 47:00 what are arrays in JS? How to insert, remove, access, sort, reverse and manipulate array elements? 01:05:34 what is Array Destructing in JS? 01:07:12 what are array-like objects in JS? 01:10:05 How to convert an array-like object into an array? 01:12:05 what are loops? what are the types of loops in JS? 01:19:10 what is the difference between for and for..of loops in JS? 01:20:40 what is the difference between for..of and for..in loops in JS? 01:22:10 what is forEach loop? Compare it with the above methods. 01:27:03 what are Functions in JS? what are the types of functions? 01:38:27 what is the difference between arguments and parameters? 01:40:54 Default Parameters in functions in JS. 01:41:50 what is the use of event handling in JS? 01:44:30 what are First-Class functions in JS? 01:44:55 what are Pure and Impure functions in JS? 01:48:53 what is Function Currying in JS? 01:51:27 call() & apply() & bind() methods in JS? 01:54:22 what is a string? 01:54:43 Template Literals and String Interpolation 01:56:15 single quotes vs double quotes vs backticks 01:56:52 String Operations in JS 01:59:01 what is string immutability? 02:00:37 Different ways to concatenate strings in JS 02:02:20 what is DOM? what is the difference between HTML and DOM? 02:04:55 How do you select, modify, or remove DOM elements? 02:05:53 Selectors in JS DOM. 02:10:47 what are the methods to manipulate elements, properties and attributes of JS DOM? 02:11:26 what is the difference between innerHTML vs textContent? 02:12:50 How to add or remove properties of HTML elements from the DOM using JS? 02:13:59 How to add or remove style of HTML elements in the DOM using JS? 02:14:55 How to create new elements in DOM using JS? 02:18:21 Error Handling in JS 02:22:56 what is Error Propagation in JS? 02:23:35 Error Handling Best Practices 02:24:37 what are the different types of error in JS? 02:26:25 what are objects in JS? 02:30:05 what is the difference between an array and an object? 02:31:00 How to manipulate Objects in JS? 02:31:37 Dot Notation vs Bracket Notation 02:33:00 How to iterate through Objects in JS? 02:34:34 How to check if a property exists or not? 02:36:00 How to clone an object? 02:40:33 Sets in JS 2:42:59 Map Object in JS 2:45:40 Events in JS 2:50:47 Event Delegation in JS 2:52:50 Event Bubbling and Event Capturing in JS 2:57:20 event.preventDefault() method in JS 2:58:28 The use of "this" keyword in the context of event handling in JS 2:59:00 How to remove (unattach) an event handler from an element in JS

[@shubhamdas7347]

very gratefull for the effort.

[@divyadharshini6916]

Thank you 🙏

[@rubeenaanwar236]

thank u..

[@MdShihabUddin-dh5vc]

Thanks

[@js_offc8436]

Thank you man, great job

[@azer9617]

Bro it's nice to live in the same world with people like you

[@interviewhappy]

Thanks great compliment @azer9617

[@fazilhakkim1091]

one of the great video I have seen ..thanks for your teaching

[@athirasekhar2033]

I cracked multiple technical rounds of 5 companies in last 2 months watching your videos. Got Job offer too.Thank you!

[@bhawnasuman9363]

Hi can you tell me some ques

[@vikiboi8129]

Can you explain about the preparation and resources you took to achieve that progress.

[@user-py1gn4kq5v]

Same i also got

[@bhawnasuman9363]

@@user-py1gn4kq5v can you tell your interview exp

[@balendrasinghparihar8849]

Can you help me

[@eramperwez187]

Very nice sir, please keep uploading and also make for typescript it's a humble request.

[@ayushshukla2655]

sir where is the most important topics closures,promises,asyc,await 😂😂

[@TejasNesarikar]

Check link in a description......buy pdf

[@adityakulkarni6204]

Excellent video sir ,sir please make one long interview questions on react js also.

[@interviewhappy]

As soon as possible @aditya

[@nikhilpatel81]

Thank you so much sir ❤ for uploading such amazing content❤

[@interviewhappy]

It's my pleasure

[@SSRathore21]

This is not just a interview question video , but the whole documentation of JavaScript in compressed form ,and really far better than those coding tutorials of 10 to 15 hours. Animations, presentation and using code examples and no garbage talking, point to point things make it seems like a paid course. You can jump to Node js or React after watching this easily Thanks a lot Sir

[@interviewhappy]

woww... tears in my eyes. They always said, make videos like other teachers where you type the code. I always said, my goal is to explain the concepts clearly & within time. My code typing will not make viewers good coders. Code yourself to become good coders.

[@Aptilover]

​@@interviewhappyno u r on the right track u explain so well and the examples that u give r do useful and easy to understand any concept i request you to please make more js interview questions as I have to prepare for it and as a fresher it's quite difficult to prepare for interview as I m a self taught person

[@its_so_not_me9747]

Qq

[@orangefield2308]

@@interviewhappy awesome video! might help to have timeline splicers in this three hour video to see questions or segments, video buffering is taking long by the way, maybe have different Part numbers to split up

[@abc-ym4zs]

any good channel like this for backend bro please bro reply me

[@ekarthika7745]

Sir after three years i have a confident for attend the interview. I bought your 500 interview questions and prepare one week now I feel I'm expert in. Net

[@interviewhappy]

Great, that is my objective. All the best for your career.

[@mounikanimma189]

How to buy. I want to buy please share details

[@shivanip1096]

I also want to buy

[@akulavara2940]

​@@mounikanimma189 Check video description

[@Aptilover]

Can you share that please

[@writer_shubh]

this is the best JS interview questions tutorial I've ever seen. Just purchased the PDF version of the notes as well, and that is helping more while understanding a particular topic. Much thanks! 🙂 UPDATE: I cleared Accenture interview after learning JS from this video.

[@Aptilover]

@writer_shubh great to hear ☺️ that can u please connect with me as I really need help coz I have to prepare for interview

[@writer_shubh]

@@Aptilover yes sure

[@Aptilover]

@writer_shubh heyyy can we connect

[@narendra2058]

​@@Aptiloverhi

[@narendra2058]

How is pdf bro

[@engineersINnight]

Hello Happy Ji. Your interviews Questions are more helped me to get 2 Offers Letters with Salary Hike. Please keep it on. These videos will help more persons like me. also Please create a 100 FAQs on jQueries too.

[@user-py1gn4kq5v]

I got job in multiple companies , thank you somuch sir

[@X_y_zaid]

Experienced or fresher?

[@vishnukumar-o5y8y]

In which company you got placed can you share details

[@user-py1gn4kq5v]

​@user-nz8sy4dq8y Infosys , TCS, Accenture

[@arijitroy8390]

He is bluffing

[@Melakusisay]

words fail me to tell you how you are the best , you did the best interview questions which touches almost all aspect of JS chapters. your voice tone is welcoming and interesting I was happy even the previous 25 question and extremely happy on this 100 additional best interview question and detail explanation. Keep up your work, you are the best ever.

[@interviewhappy]

Thanks captain America. You touched me. People getting jobs and these kind of words are my motivation. I will try my best and everyone else also please do.

[@Melakusisay]

I bought the Udemy resource package, it is very usefull and valuable fair price, you deserve more than this prise !!!

[@akshayshelar7627]

At 56.30 Timing , For concat method we can also modify the same array, right ? array = [1,2] array.push(3,4) console.log('Push method',array) array = array.concat(3,4) console.log('concat method', array)

[@g.pavani5275]

Very good explanation, till what experience level this questions will be useful ? and I am trying to buy udemy course is that updated version only ?

[@beingcheercool]

lots of love to you sir! Big Thanks again for uploading such amazing content 😍

[@interviewhappy]

Thanks cool and all the best for your career.

[@vikasme1299]

Sir please 1 HTML, CSS, JS and React ka combo offer laao na 500 Questions ka or please coupon code bhi batao❤

[@harshthosar8600]

9:00 I have always had this question in my mind. No interviewer had asked me this, but I always had this doubt. Thank you, sir, for covering everything with such details.

[@Aptilover]

Half part is free and half is paid ..of your course

[@interviewhappy]

yes

[@tanusingh4082]

I tried but faild convert like an array-like object into an array var obj = {0:'a',1:'b'} var arr = [...obj] console.log(arr) obj is not iterable

[@NainiPhp]

please can top100 question make in reactjs

[@beingcheercool]

yes we want it sir, request..

[@programmershub3144]

Yes we want react from you sir

[@interviewhappy]

That is my next target.

[@beingcheercool]

@@interviewhappy we are waiting!! 😁

[@yelagandulasridhar7011]

Hi sir, Please can add Design Patterns videos.

[@interviewhappy]

Sure, Azure, React and Design Patterns are next target.

[@vineethrathna]

i have a littele confsuion on differnce between primitive and non primitive data type question in that u said ,we assign a new value to the varible it stored in new location as of my knowldge In JavaScript, primitive data types (such as numbers, strings, and booleans) are indeed immutable. When you assign a new value to a variable holding a primitive type, the new value is stored in the same memory location. kindly expalin this sir which one is correct

[@rajamech2455]

Hi sir, Thank you for your video, I cleared first round in interview because of you also. But I am failed 2nd round. please can you upload 2 advanced javascript video...

[@bhaviljainnnnnnn]

Please share the advanced topics asked to you

[@joshuakemougne6471]

Sir i just love the graphical representations infact am 100% confident in js now. you just so explain it even my grandmom will understand if she were still alive arigato🙏

[@interviewhappy]

You made my day man. Best compliment. All the best for your career from bottom of my heart.

[@PrakashG-qt1pp]

can u plz tell me this is use for experienced candidates also....?

[@engineersINnight]

Please make a "Top 100 [ jQUERY ] Interview Questions and Answers" also

[@interviewhappy]

I will try

[@srikarravoori124]

I have completed one hour and will complete the remaining soon. Really its simple and easy to understand. The video is prepared with utmost care interms of presentation. For the interview candidates , its one stop to cover all js questions.Thank you.

[@interviewhappy]

Thanks for appreciating my efforts. @srikarravoori

[@adityasandge7474]

Sir!! please try to add time stamps

[@kalyanbellamkonda8653]

Sir very good session great sir thank you Love from Andhrapradesh

[@RavindraSingh-lp9pl]

please bring DSA questions as well. they are asked many times

[@interviewhappy]

Yes I know, may be I will try in future.

[@ARUNKUMAR-ql9dj]

why tupeof(null) is object? can you please explain

[@shesparks64]

Do it for react also pls and then separate for complete' frontend interview '

[@tusharutane8031]

Finally completed whole video feeling confident and thank you so much sir for this amazing video and the explanation was amazing.Best wishes for you

[@interviewhappy]

Thanks Tushar and all the best for your career.

[@perambalakrishnareddy8633]

Can you prepare the interview questions for experienced candidates with real time examples

[@ajaychoudhary8955]

Please add timestamps at least for the main topics

[@csstudent624]

Sir i am from Pakistan mai kese purchase karunga website mai sirf india ka option diya hai

[@JaiBhisht]

udemy coupon code expired sir , i want to buy it please extend offer duration

[@JSK_98378]

Sir please do Reactjs top 100 interview questions , please dir

[@interviewhappy]

Sure that is my next plan. All the best for your career.

[@shortstories2283]

Sir please upload react interview questions please

[@MrLaxman007007]

bro here in the clip starting typeof null is an object not null. please look into it

[@harshbobby1911]

Sir in 100 questions ka list mil jaayega as pdf ?

[@RamMurti-pu1nt]

Sir please extend offer duration, I want to buy the course

[@narinderkmaurya]

You saved my life before the interview, thankyou so much!!!!!!!

[@interviewhappy]

Your Welcome

[@gopipanguluri5663]

Awesome explanation, great work thanks for this video and udemy course 🙂

[@interviewhappy]

Glad it was helpful!

[@arunkumarsalluri9988]

But I am not finding the pdf of javascript interview questions and answers please

[@interviewhappy]

The link is in the video description.

[@harshjaiswal9926]

In JavaScript, when you declare a variable and assign it a primitive value, such as var a = 30;, the memory is allocated to store the value 30 in a specific location. Later, if you write a = 45;, it doesn't mean that a new memory location is allocated. Instead, the value at the existing memory location is updated to 45. But sir, you said different memory is allocated.sir,could you please verify your answer.

[@interviewhappy]

New location means, new memory address. That is immutability. Explore more.

[@PREMSINGH-fm9ds]

It would be great if you add your courses in udemy business. As most of the working people have access to udemy business from the company so that they can enroll and learn. Thank you for helping all the job seekers with the great contents.

[@interviewhappy]

Maybe one day!

[@PREMSINGH-fm9ds]

Thank you Sir for awesome content ​@@interviewhappy

[@MANAUWARALAM-te7fb]

Completed in two days. Awesome content is given by giving such a nice explaination. Seems like revising whole js. Very good and usefull video.

[@interviewhappy]

Thanks a ton

[@JaiBhisht]

udemy coupon code expired sir , please extend offer duration

[@arunkumarsalluri9988]

Hai sir I just purchased your javascript course.payment has done

[@interviewhappy]

Hope you enjoy it!

[@giorgimindiashvili3810]

Happy I have another interview tomorrow and I'm here again enjoying your video and again thank you for that perfect video

[@interviewhappy]

Good luck!!

[@giorgimindiashvili3810]

@@interviewhappy I get a job as a frontend developer in big company, thank you so much again, god bless you you are very good person ♥️♥️♥️

[@2784raj]

you are doing awesome jobs by helping communities, i have learned a lott from you, you are true inspiration... Thanks a lott for making such amaizing content..

[@interviewhappy]

Thanks Raj and all the best for your career.

[@RamMurti-pu1nt]

Sir please extend offer duration , I want to buy

[@prakashpatasani-vu5uv]

If you want to help many students for crack her interview, so why are you taking cost of 200 advance interview questions pdf. Please provide free all the interview questions and answers.

[@interviewhappy]

My 60% content is free which can easily get job for freshers and upto 3years experience candidates. Then I also have to think about my Roti.

[@amanchaurasiya9677]

It was great video thank you for your hard work in helping us to get all the concepts at one place. But I think there's so many imp ques are not listed like Promises, Closures, Microtask and Macro task queues, event loop, etc. Can u pls make a same video on these concepts as well ?

[@interviewhappy]

Thanks Aman.. more questions are there in full course. All the best for you career.

[@smartygaming9131]

Nice sir it's mostly all are the interview questions are covered,and as a fresher it's very very useful for me for the interview. Sir I support you and also make more videos on other technology like Node.js MySQL, Java etc.....keep it up....👍👍

[@kumarutkarshuk_]

Sir, can you please give timestamps for this video as well? It will really help.

[@44_krishnaneema50]

PLEASE PROVIDE CUPON CODE TO PURCHASE UDAMEY COURSE

[@esthersharon7608]

Woah! An amazing course. Got to know a lot. Thankyou sir!

[@interviewhappy]

Glad you liked it

[@kuldeepdawar7496]

Thanks for this video Brother, your explanation is very clear and wisely. You are helping a lot by this content thanks.. I am looking React videos like that explanation..🙂

[@zkhan1995]

add time stamps please

[@interviewhappy]

ahh.. 100 questions, bit difficult. I will try

[@lifewithomar05]

Todya I joined in a IT farm as a MERN Stack developer. Your videos are really help me to get the job.

[@RohitSingh-pl5wi]

Bro which company?

[@tanishajaiswal7559]

can you please refer me . i have 1 year of experience working as a NodeJS developer

[@patilrahul515]

Please make a video on vue.js interview

[@mayurdas9526]

please make same kind of video on java and spring boot also

[@knowledgeable...3609]

Sir pls ek video hindi mai banao...

[@interviewhappy]

Mera happy rawat karke ek Hindi channel hai.. subscribe it.

[@YerramsettyVinay]

It is very usefull and also can you prepare html and css interview questions and answers . it is use full to good idea about of the static pages . mainly usefull the freshers... because dont idea about of the course sir

[@interviewhappy]

Sure, I will try to do for css and html also. All the best for your career.

[@bharathy83]

Hi sir thank you for the video. Pls add design patterns videos

[@interviewhappy]

Design Patterns may take some time but will come soon.

[@saifalisanadi6519]

Thanks for such amazing collection of interview questions, it's really helpful. I have a request, can you make single video by collecting all C# interview questions.. that would be great help. 😄

[@jyotisaxena9014]

This is so good. You are so clear. From where I can get all your resources in JS. Do you have node.js ques also.

[@interviewhappy]

Thanks. First React and then Node I will launch

[@HarshavardhanaB-b2f]

Hi Happy, Just completed all questions and made a notes, preparing for interview. Thanks for your free Video tutorial.

[@interviewhappy]

Just post a comment whenever you crack the interviews. That's my motivation.

[@Gameflix548]

thanks a lot , i cracked multiple angular interviews due to this . changed my life.

[@MdMeraj-kq2he]

bro r u experience candidate or fresher

[@sumannayak7677]

how many years exp u have?

[@Gameflix548]

3 yrs@@sumannayak7677

[@rolex1189]

Sir late passedouts can get a chance for job sir

[@adilkevin6220]

Hi Admin, Your content is good do mind adding async await promise promise.race,promise.all concepts as well. Protoype inheritance cors errors. What happens when you add async or defer keyword to the script tag and there order of exection. Event loop concepts since JavaScript is single thread how does it handle concurrent request. If condition and loops I don't think interviewers will be interested in asking question as it is present in all the programming language.debouncing/throttling and function curry and how to write polyfill for bind method concept also has been skipped. Please come up with all the concept

[@interviewhappy]

First I want to cover all basics. Advance is very wide and it depends on what you have have worked. But basics are common and more important for candidates with less experience.

[@adilkevin6220]

@@interviewhappy I understand if you could add the above topics as well viewers will get benefit out of it.

[@adilwahla544]

I got offer & yes your videos helped me to crack interview MERN stack and Js + SQL So, thank you very much ❤

[@amirtha407]

Javascript is a Scripting language or Programming language ????

[@VVigneshwaranMSEC]

Scripting language

[@dawatedeenofficial3237]

Thank you sir for such useful and informative videos. Would you please make videos on MongoDB and nodejs or backend

[@interviewhappy]

That's in plan. All the best for your career.

[@vishalkothari8065]

In the video in the cloneNode method h1 tag is removed in the example given will it happen so ?

[@interviewhappy]

You can try by yourself.

[@namansharma8346]

sir please extend the discount offer on udemy i want to buy sir really

[@namansharma8346]

thank you very much sir , so kind of you.

[@TheRiderzx6r]

Best 3 hours I ve spent on youtube ! I have an technical interview and need to gather as much info as possible, watched also the 2 hour Angular questions and this 3 hours one about Javascript, very well explained and refreshing for the memory, I feel ready for the technical interview! Let s get it !

[@MdMeraj-kq2he]

bro are u fresher or experience candidate

[@TheRiderzx6r]

@@MdMeraj-kq2he experienced ish , 2 years

[@MdMeraj-kq2he]

@@TheRiderzx6r ok bro tq

[@yashshrivastava280]

did you clear or not ?

[@Chad-pi5if]

let age = 25; age = 30; In this question both the age variable are exact same and holds the value first 30 and later 25 at the same memory location. Please make a correction.

[@sahil_karamkar0146]

I got more clarity in js tq sir. 👌👌🥳💯💯

[@dilipkumarmattewada7163]

Good explanation covered all topics.. Please make one video for python - experienced

[@Rohit_ideas]

hiii sir plz help me to solve this question const a = Ashwani@97 output = 79inawh@sa help me to solve this

[@shobhag9121]

Sir can u teach project on javascript

[@Aptilover]

Your interview course of javascript is enough to crack the fresher interview?

[@interviewhappy]

Yes it is for JS interview

[@nitinjoshi1020]

sir please redux ke interbiew question ke uper bideo bana dijina naa...

[@kiranpylla]

want to start with some course for my next job. I will start with this and try to complete this. I don't know how many days i will take. I just started. May be to get accustomed to learning after working hours takes time. But at least i will start today. If there are anyone want to join and completed together then we can discuss if you have any doubts. Lets start!

[@nunov.f7910]

Question: minute 46, shouldn't the variable called "remaining" be the "restArguments" defined with the rest operator on the function arguments?

[@vidhyanadarajan7873]

very good start Sir, we can master JS by practicing your interview questions. i found few errors, one of them is at 1:30:15. function declaration, at console.log you have mentioned add instead of sum. so there is error to print the output. but its not major issue. your interview questions built confidence to attend interviews and knowing JS very important. im practicing every day little by little sir thanks. i want t buy the pdf but im from spain dont have choice to buy. plase give us an option to buy sir thank you.

[@wowameer]

@Bro... You are really awesome. You also made things very easy to understand; your explanation and graphics are very informative. Good Job.

[@JackSadi]

2:56:20 confused between the Event Delegating and Capturing. Also not clear how Event Delegate works under the hood

[@gufababa7504]

Sir please make laravel and react js interview preparation in your website

[@interviewhappy]

React I will make soon.

[@chandangoud9995]

Hai, sir i really like your videos of explanation actually i need small suggestion from you regarding programming languages so actually i had learned python,javascript,html,css and sql is this enough to future for developers and some what of django also i know

[@dios8256]

This is pre interview gold thanks mate.

[@interviewhappy]

Glad you think so!

[@seek2learn98]

hi , i bought your react , node courses , both are so detailed , can you plaese make same for java and sppring boot . would b great help .thanks😊

[@arifk7838]

Sir please upload same for MERN STACK and python

[@interviewhappy]

Sure I will try

[@charan3998]

can you please add the time stamps, it'll be of great help to navigate while revising the content. Thank you for such a huge resource.

[@yashveersingh994]

Please make a video on react 100 questions

[@interviewhappy]

Sure, I will try to do it soon.