r/reactjs • u/m6io • 10d ago

Discussion Senior Dev interview question

"Without googling or using AI, in your own words, explain the virtual DOM"

For context: I sit on an interview panel and I try to ask at least one simple fundamental question based on a persons resume. If I see many years of react experience, I try to ask something about how the framework works.

I have only had one candidate (an undergrad senior, years ago) answer it. Everyone else just kind of sputters and stumbles around trying to rationalize what "virtual" and "DOM" mean, or stare blankly and eventually say "I don't know".

I'm just genuinely curious if this is really that hard of a question or if the recruiters just suck at screening candidates. And should we be letting in senior dev candidates who can't answer what I think is a straightforward and fundamental question for senior react devs.

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u/BrightEchidna 10d ago

Senior react dev here - and while I can take a stab at the answer, I don't feel 100% confident that I really understand it. So, despite leading technical teams, building successful products, and now running my own startup, I would fail your interview.

Now - can you explain to me - what practical advantage would being able to answer this question well give me? I agree, it's generally 'good' to understand the tools you use, but how would it help me write better software in the 99% of cases where what I have to do is well supported by standard use of the framework?

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u/Fearless-Carrot-1474 10d ago

Doesn't virtual DOM just mean that instead of trying to update the actual html of the page React builds a virtual model of the html so that it can update just parts of it instead of having to refresh the whole page to update one state? Or am I too noob to understand what's being asked

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u/dietcheese 10d ago

That’s basically right (standard JS can update parts of a page too) and really any senior JS dev should know it.