React Keys & Rendering Quiz

Ten questions with per-question explanations about keys, reconciliation, state and memo. Score is local and is never stored or sent.

react-key-quizLOCAL WORKSPACE

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Inputs and settings1. Which key preserves item identity after sorting?2. Does changing a component key reset its state?3. Are keys passed as ordinary component props?4. Where must list keys be unique?5. Does memo prevent every rerender?6. Should randomUUID run for every key during render?7. Does an inline new object retain reference identity?8. Is useId designed for list keys?9. Does state stay tied to the same tree position and type?10. Does mutating an object then setting the same reference guarantee a rerender?

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Processing model and limits

Ten questions with per-question explanations about keys, reconciliation, state and memo. Score is local and is never stored or sent.

Data and model checked: 2026-10-21Official reference ↗

How to use this tool

Load the example, confirm field units and processing rules, then run locally. Editing any input clears the old result. Copy or download the complete output explicitly.

When not to use it

Ten questions with per-question explanations about keys, reconciliation, state and memo. Score is local and is never stored or sent.

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React Keys & Rendering Quiz

Results

Processing model and limits

How to use this tool

When not to use it