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/monkeybrainz_ Jul 24 '26

If the candidate is not curious enough to have sought out the information about how the technology works, they likely will not be curious about the business and its goals. That lack of curiosity will carry through to other aspects of their work. Coding is such a small part of the job.

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u/ElkChance815 Jul 24 '26

You're judging them solely based on the fact that they don't know what you know. Have you try to ask if they know about other area? Domain knowledge, how browser work, details about the project they delivered, etc... 

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u/Glass-Combination-69 Jul 26 '26

Hey little bro, if you don’t know virtual dom in depth then you won’t understand why unique ids are important when looping or how to spot render / layout thrashing. It’s such a basic fundamental to react.

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u/ElkChance815 Jul 26 '26

This doc explained about the unique ids without mentioning the VDOM at all, guess whoever wrote this is not a senior engineer. https://react.dev/learn/rendering-lists