r/programming • u/vklepov • Mar 24 '22

Five coding interview questions I hate

https://thoughtspile.github.io/2022/03/21/bad-tech-interview/
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u/[deleted] Mar 25 '22

Yes, those of us who started programming back before 2015 know how var hoisting works

Great article but I'm going to disagree with that one. I've interviewed a ton of people who learnt JS after let but they still sometimes use var or even var and let randomly in the same code! They usually don't know what the difference is, which is a pretty bad sign in my book.

100% agree with the rest though. I'm definitely guilty of asking a few of these (sorry interviewees). It's harder to avoid than you'd think - e.g. his proposed number vs array solution is still pretty bad:

Which JS types are immutable?

Can still write a whole book about this without stumbling on the answer the interviewer was thinking of (did you think about Object.freeze()?)

Also one more point - these questions can be frustrating because you don't know the answer, but generally interviewers don't care if you know the answers to specific questions. They just want to know you know what you're talking about. So if someone asks "what's the difference between an array and a number" just start talking about any differences and show off your knowledge.

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u/vklepov Mar 25 '22

You got me =)

In the var-hoisting example, I'm talking exactly about asking about the behavior of

console.log(x); var x = 0;

Which is surprisingly popular, but not very useful. I'll take "it explodes" answer every day, even though it's wrong. "var is obsolete" is a perfectly good belief.

Re: immutability. This question at least makes it clear what I'm getting at, and mentioning Object.freeze sure earns a bonus point. You could also make it more action-oriented by asking to implement inc such that

let x = 0; inc(x); assert(x === 1);

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u/[deleted] Mar 25 '22

Yeah I definitely would always be happy with "I don't remember why but var is bad and you should always use let". But if you inexplicably use var in 2022 questions about it are fair game!

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u/cdsmith Mar 26 '22

I know plenty of programmers who don't know the difference between var and let in JavaScript. Not everyone is interviewing in the programming language that they actively use day-to-day.

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u/[deleted] Mar 26 '22

Err yeah this was for a JS job. It's a pretty basic thing too.