10 JavaScript Interview Questions You HAVE TO KNOW

Can you pass this JavaScript interview? Here are 10 questions you should be able to answer!

**Newsletter**

**DISCORD**

**QUESTIONS ABOUT MY SETUP**

[Diego_Cabrera]

Literally perfect timing man. I’m waiting to hear back if from my first interview and I’ll be assigned to pair program with a dev at the company. I’m quite knowledgeable but there are areas where I could brush up on. Thanks so much!

[billyfigueroa]

James is an AI machine 😂 dude hit a infinite loop glitch the last 10 seconds 😂😂😂

[economicist]

Wow, I guess I know a lot more about JS than I thought. I still have a ways to go but this is pretty encouraging.

[Gamewithstyle]

So nearly 50% of these are for if you’re interviewing for a react job. It’s likely you are, but it’s so important that you understand larger JavaScript concepts. There is one question about scope in this list, and it’s something juniors trip up on constantly. If you can tell me what a react hook is, but you don’t know what hoisting means, or the difference between const and let, then something went sideways at some point.

[slacle]

Hey James, where can I follow along for updates?

[KAZVorpal]

Actually, console.log DEFINITELY counts as a side effect, RE pure functions.
So does printing to the screen, or saving to a file.
This is slightly different than how you are still allowed to print in a Java function declared as "void", because that ONLY applies to (not) returning data, rather than to all mutation.

[simonswiss]

Thanks for making that video! I always assumed I would BOMB tech interviews and thought I'd struggle through this video. But I watched all of it, paused right after seeing the question and did my explanation. I think I nailed 9 out of 10 questions — the first one (closures) being the one I am not capable of explaining fluently. I know what closures are, but have a hard time explaining why they're important and useful. Everything else I feel like I could talk confidently about, and wouldn't be worried about digging a bit deeper if necessary. Closure, I felt like I was bullsh#tting my way through the explanation lol

[alanthomasgramont]

The issue I see most with people understanding promises is what actually happens during the “async” part. Most inexperienced developers don’t understand the event loop, which causes problems especially in unit testing and mocking.

[pavfrang]

Thanks for the review! A pure function should not write to a file, because the file could indirectly affect state and therefore affect the result.

[Shagidelic]

Please note TS only provides IDE level type safety. There is no compile time or runtime type safety.
Meaning? Type checking errors will only occur if you are using an iDE that has linting or has basic type checks. Since TS still allows dynamic variables it has lots of type unsafe stuff allowed. When it is transplied into JS, even static type checks are gone and Runtime type checking also doesn't exist.

[chandrashekar-usef]

What is the output of a URL on a browser for SPA vs MPA

[nathangwyn]

I knew them all!! I'm 3.4yrs into teaching myself. I'm currently hoping between JS, TS, GO & Rust... mainly JS/Rust atm.

[AlexandreMoreauLemay]

Console logging can be considered a side effect in specific situations; one of which is if you use stdin/stdout to pass values into buffers of different subprocesses. An unexpected console log can mess this up

[ManfredSpecht]

Thanx for the cool video. I was maybe missing the new features we got in the modern ECMA-Script world, object oriented programming in JavaScript, classes vs. prototypes, maybe deeper functional things like currying and stuff. I personally do not like those kind of questions. I like a more pragmatic approach.

[MichaelMooregrownman]

Wow James what are the odds with me having a 2 hour coding challenge coming up and you make this video. Thanks

[incarnateTheGreat]

I never liked the Closures or Function Composition questions. Everything else for the most part seem more relevant to modern development. I suppose the first questions are more for core/library development.

[dev-akeel]

3:54 that was first thing what triggered in my mind after hearing the word "side effect".

[Thirteen]

Lol, there's a mess-up with the audio at the end

[giant]

I do small projects never feel like need to use Typescript...

[wchorski]

the most important thing is to make sure you have fun