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JavaScript Interview questions everyone gets wrong 

Catherine Li
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In this video I’m going over MORE JavaScript interview questions that you might encounter in your software developer interviews. This video will feature questions that really test your understanding of common pitfalls and weird parts of JavaScript, such as “this” keyword and scope chain.
Click here for a playlist of all of my JavaScript Interview and tutorial questions: bit.ly/3Gr54ce
Subscribe to my channel! bit.ly/3DBIIRj

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28 сен 2024

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Комментарии : 74   
@artemsapegin
@artemsapegin 9 месяцев назад
The correct answer to all of these: it won’t pass code review.
@triggerticker
@triggerticker 8 месяцев назад
It's crazy to me that after 4 years of uni, now that I am lookinf for a new job, I am looking at this vids to prepare for interview. Most concepts aren't really used at all in real life and thus things get forgotten. Makes you question the real use of these questions xD Anyways thanks for the great vid
@catherinelijs
@catherinelijs 6 месяцев назад
Thank you and you got this! Were you able to find a job in the past 2 months?
@betatester03
@betatester03 3 месяца назад
Javascript is such an obnoxious language.
@alexandersnider734
@alexandersnider734 Год назад
These are definitely good academic things to know to understand some of Javascript's history and design philosophy, but any company actually asking me this many questions about my understanding of "this" and "var" would make my really wary of moving forward. This would indicate to me that first, the company might still be using var in practice which for all intents and purposes is almost always the worst option to use for instantiation, and that second the company might be using JS for OOP, which would indicate to me a big mistake, as JS really shines now with a functional focus and there are much better languages to use for OOP. I will concede though its important to understand the context of the arrow function vs a functional declaration. I would say much more important and likely questions to get in a modern JS interview, relate to especially closures, first-class functions, and might even touch on typing with TS.
@TuanNguyen-ed9rb
@TuanNguyen-ed9rb 2 месяца назад
why don't you think that the company is using let in their code, and they want to find a candidate that know the difference between var and let so they don't screw their code by using var everywhere?
@martapfahl940
@martapfahl940 Год назад
Do they really still ask questions including var ? I literally NEVER use var
@6-dpegasus425
@6-dpegasus425 Год назад
Same I only ever use let or const
@MrChicano101
@MrChicano101 Год назад
Yea
@KAZVorpal
@KAZVorpal 2 месяца назад
That's why you don't commit the obscenity of putting the curly braces on the next line. They go on the same line as the statement. Always.
@haidermansoor4760
@haidermansoor4760 6 месяцев назад
I specifically search for your videos lol. they have helped me previously in my interviews alot. Thanks alot Chatherine 🙌
@catherinelijs
@catherinelijs 6 месяцев назад
Thank you! I have lots more content ready so I'm really hoping it will be helpful!
@keifer7813
@keifer7813 11 месяцев назад
The more I watch these vids, the more I cringe at my prior confidence in JavaScript
@costcomembership4617
@costcomembership4617 Год назад
How common are questions regarding var vs let and arrow funcs vs normal funcs? I started learning JS self taught around June of 2022 so almost everything I’ve learned and built has been with the latest syntax. Would you recommend learning more about pre-es6 topics solely to prep for interviews?
@catherinelijs
@catherinelijs Год назад
Your main focus should be ES6 and modern JS and frameworks. That’s where we’re all headed. For older tech companies you can look at pre-es6 topics but that’s a lower priority imo
@MehdiGlz
@MehdiGlz Год назад
Hey Costco Membership, I know this is an old comment, but for anyone out there: ime this is important to know for interviews. Last year I did a ton of interviews and these questions came up more than once, both at small companies with old stacks and big international consulting companies. So it's good to study up before interviews
@madimakes
@madimakes 5 месяцев назад
canadian confirmed, lol. also...on the first one, i've been doing python the past 2 months and i'm going to be ruined when i get back to JS...now to watch the rest of this video
@oghenefejiroprinceimene6090
@oghenefejiroprinceimene6090 Месяц назад
This was really nice
@Phearzmeh1
@Phearzmeh1 11 месяцев назад
Thanks i never really understood arrow functions but this helps
@catherinelijs
@catherinelijs 9 месяцев назад
Happy to help!
@lunchboxUFX
@lunchboxUFX Год назад
in the last question, b++ of inner() is incrementing var b = 2 of outer(), correct? (This is a closure, yes?)
@petrkavulok9753
@petrkavulok9753 Год назад
Hi Harold, it is not. in this case it appears as the line 5 is ignored completely and the console logs only line 6 in an unchanged form. To get a better understanding, look up JavaScript Hoisting. Cheers
@myPrzeslaw
@myPrzeslaw 4 месяца назад
@@petrkavulok9753 Well, line 5 isn't ignored, it assigns NaN value to local b var (as NaN is valid result of incrementing undefined in js). But that value isn't logged and is overwritten in line 6 by the value 3.
@myPrzeslaw
@myPrzeslaw 4 месяца назад
No. It would be a closure if line 6 did't existed (or existed without 'var' keyword). Once you declare var x anywhere in the function (even in its last line) THE WHOLE SCOPE OF FUNCTION don't have access to outer scope var x at ANY LINE (even BEFORE initialization).
@TamPham-oe2xc
@TamPham-oe2xc Год назад
You better than my teacher 😂
@cabbage-dev
@cabbage-dev Год назад
Some of these questions appear to be made before linters existed and its a wonder they keep being asked
@crowtek2503
@crowtek2503 Год назад
Thank you for the tips 😊
@margaret8114
@margaret8114 11 месяцев назад
So helpful!
@catherinelijs
@catherinelijs 11 месяцев назад
Thanks so much!
@MengLinMaker
@MengLinMaker Год назад
I prefer to use "const" if possible, then "let" and avoid "var" due to the strange behaviours it causes
@myPrzeslaw
@myPrzeslaw 4 месяца назад
And it's great and modern approach but if company you applying to also maintains some pre ES6 code it is valid approach to examine candidates it that regard.
@computeraidedyami
@computeraidedyami Год назад
You are like a god
@ziadomar5057
@ziadomar5057 Год назад
Thank you and you are so beautiful
@anasouardini
@anasouardini Год назад
If only JS and browsers didn't suck, interviewers wouldn't have the chance to ask us these useless stupid questions. In the question about `setTimeout`, it's not because it's asyncronous but because browsers copy references instead of values.
@myPrzeslaw
@myPrzeslaw 4 месяца назад
I don't think working as a JS dev is anyhow mandatory. But if you intend to do, it's pretty important to understand how do closures work.
@CaliburPANDAs
@CaliburPANDAs Год назад
Welcome back Catherine :) do you has twitter?
@catherinelijs
@catherinelijs Год назад
Thanks! I’m setting up new social media accounts and will post the links on this channel soon
@dbarless
@dbarless 11 месяцев назад
always. add. semicolons.
@КатяСаввова
@КатяСаввова 4 месяца назад
always; add; semicolons;
@josecastroesq
@josecastroesq Год назад
This video is gold. 🪙 Thank you for your content!
@catherinelijs
@catherinelijs Год назад
Thank you!
@k-yo
@k-yo 2 месяца назад
Honestly, these kinds of trick questions are really dumb. It tests a subset of edge-cases you wont usually stumble upon on real projects. I hate this.
@josem3933
@josem3933 Год назад
Have an interview tomorrow and have been binge watching all your videos
@catherinelijs
@catherinelijs Год назад
Thank you! I hope you got it!
@LucianoClassicalGuitar
@LucianoClassicalGuitar 5 месяцев назад
How did it go lol
@meetkass
@meetkass Год назад
Binging all of these videos now that I am expecting some tech interviews. This is also great insight! I wish I was looking these up BEFORE when I was giving interviews. Thanks!
@downanddirtytruth
@downanddirtytruth 9 месяцев назад
Well. I'd have failed... I haven't invested much time into var. It's throwing me off quite badly.
@TokyoXtreme
@TokyoXtreme 3 месяца назад
Me in 2024: "Did var ever exist in JavaScript? I've never seen it in any codebase."
@FelipeBasilio-s3o
@FelipeBasilio-s3o 3 месяца назад
Awesome video!
@catherinelijs
@catherinelijs 3 месяца назад
Thanks Felipe!
@anuj1994k
@anuj1994k 9 месяцев назад
I like it somuch.... kindly do more vdo based questions on javascript function
@ohyr8948
@ohyr8948 Год назад
Can I Wait for your INTERESTING front-end web devlopment course?
@adrianibarra9589
@adrianibarra9589 Год назад
LOL i have 3 years of experience and the first one got me haha
@srirampaga2249
@srirampaga2249 3 месяца назад
At 3:27, the settimeout example, it prints 5, 5 times. I have a question, how can it print 5 when the for Condition is false since i=5, but condition says i
@adeimpossible1425
@adeimpossible1425 2 месяца назад
2:49 it’s because setTimeout runs after the for loop is completed. At that point “i” is 5. In the desired implementation “i” still goes to 5 and satisfies the for loop’s condition which then prints out the values of i WHILE i is less than 5
@islamfahmy9784
@islamfahmy9784 9 месяцев назад
Thank you so much
@aten488
@aten488 Год назад
Thank you for this video. Much needed :) .
@C0D3O
@C0D3O Год назад
const happy = new Year('🌟')
@catherinelijs
@catherinelijs Год назад
Same to you! All the best in 2023
@maksworldwebboy1119
@maksworldwebboy1119 9 месяцев назад
The answer for the last question is Nan ;)
@myPrzeslaw
@myPrzeslaw 4 месяца назад
No, NaN indeed is the result of incrementation in line 5 but it is not console logged. Console logs the result of assignment from line 6.
@stewart6395
@stewart6395 Год назад
Really love these old school questions ❤ Everyone should know this
@Gio-m
@Gio-m 7 месяцев назад
Wow, super straightforward thanks Catherine!
@catherinelijs
@catherinelijs 6 месяцев назад
Thanks!
@nittamonisudeepchand5325
@nittamonisudeepchand5325 Год назад
😍
@thisisYirou
@thisisYirou Год назад
The second example, console.log(x) would actually return 21 instead of undefined. Yes variable x is hoisted, but code runs from line 1 and below. So if girl() is invoked, that means at that point x is initialized with the value of 21. (if you try in your browser)
@tunacant9106
@tunacant9106 Год назад
Nah, it would be undefined, because inside the girl function, x is undefined.
@vivekcse1
@vivekcse1 Год назад
@@tunacant9106 On Mac, it gave me 21. Let me try it on PC.
@vivekcse1
@vivekcse1 Год назад
On windows also it's giving me 21. So this girl's premise is false. This is like a closure. But the higher order function being non-existent, global scope is taking over.
@agmonblynkos
@agmonblynkos Год назад
​@@vivekcse1the real reason it logs 21 is because var is also adding the variable to the window, which is where the console.log takes the result from. Try with let or const, it will log undefined
@myPrzeslaw
@myPrzeslaw 4 месяца назад
It's not. JS hoisting is performed before running the code. It means interpreter firstly moves all the local vars declarations to the top of the scope (but leaves initializations in its original line). The only way var x still has its value from higher scope it has to not be declared ANYWHERE inside girl-scope.
@gourabsarker9552
@gourabsarker9552 Год назад
Mam how much do you earn as a software engineer? Plz reply. Thanks a lot.
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