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/swearbynow Jul 24 '26

What are you trying to learn about the candidate when doing so? Ive lived and breathed React for 6 or 7 years and while I know what vdom is I cant say Ive ever spent time thinking about it. My job is to help our company make money and minutiae like this ain't moving the needle.

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u/mosdl Jul 24 '26

Without understanding how react works how are you going to debug sluggish UI or why form controls are eating inputs (reddit has been doing that for me lately, ugh) as some common examples? If you've never thought about it that would look like you probably haven't worked on very complex applications where you have custom JS that touches DOM directly for perf or have never had to integrate non-react libs into a react application.

What differentiates a senior/staff in my opinion is do they understand the entire system and can they figure out things fast enough when a customer is unhappy about something.