How does React reconciliation work?
PICTURE THIS: 1, 2, 2, 8
Simple meaning
React compares the new element tree with the previous one by type and key.
WHY — React instead of guessing?
Why interviewers care about React:
question about React.
trade-offs, and what you would actually do on a Frontend project - not buzzwords.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1React compares the new
element tree with the previous one by type and key.
- 2Same type means it
updates props on the existing instance
- 3different type means unmount
and remount.
- 4Keys on lists are
how it matches siblings that moved.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
React compares the new element tree with the previous one by type and key. Same type means it updates props on the existing instance