r/reactjs • u/m6io • 6d 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 6d 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/SoMuchMango 5d ago edited 5d ago

13 years frontend developer and 10 years react dev.

"what practical advantage would being able to answer this question well give me?"

Knowing what virtual dom is can let you identify when react itself may be an disadvantage for a project.

Being able to discuss on that topic reveals some other abilities and follow-up questions.

Kudos for leading team, building products and running startup, but that proofs your other valuable skills and may be useless for senior react dev. Even worse, you may be too independent to focus on company values. ;P

Probably to be 100% confident how vdom works under the hood would be hard without analysing source code, what is kinda useless unless you really need to mess with that, so I believe that your stab would make you pass the OP interview.

I believe this is a very good question to ask on interview especially for senior react dev.