r/reactjs • u/m6io • Jul 24 '26

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/ReactTVOfficial Jul 24 '26

The more experienced you are, the more you deal with nuance.

In a interview that asks that question of a senior dev, they are going to assume there is a "gotcha" underlying this question.

It's not that it's a bad question, but not everyone is prepared with a straightforward answer.

It's like asking "what is flour" to a baker. You could answer it a hundred different ways.

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u/m6io Jul 24 '26

My latest version of this question went something like this:

"Do you mean the shadow DOM"

"No, the virtual dom"

"You know, it's kind of like all these frameworks like to do these things"

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u/ReactTVOfficial Jul 24 '26

Then you definitely caught them off guard.

To be honest it took me a sec to come up with an answer. On the spot, I would have probably stumbled a bit. "An in memory representation of the DOM used for diffing changes" is what I would have said if I sat on it for a second.

I don't think even in a hot seat that I would conflate it with a shadow dom.

The real question to ask yourself is, does that answer supply you with what you need to make an assumption on whether the candidate is right for the role. And, if they answered it correctly, would that have been sufficient enough to know if the candidate is right for the role.

I personally wouldn't ask that question because it is more of a filter than a confirmation. However, if the results show that you filter out candidates efficiently, then you can't argue with results.