Answer
React only cleans up effects from committed renders; work-in-progress renders are discarded without cleanup.
Quick Answer
Effect cleanup timing in concurrent mode: React runs cleanup when a component unmounts, or before re-running an effect. In concurrent mode, React may start rendering a component, then abort and discard it before committing — effects don't run for aborted renders. Cleanup runs only for effects that were actually committed to the DOM.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ