The React Bugs I Keep Finding in Pull Requests
I review React PRs all week. These 5 bugs keep showing up: a memo that does nothing, a useCallback hiding the real fix, a SyntheticEvent that vanishes, a stale closure interval, and a batching surprise. Each one is the actual diff I left.
Question Bundle
JavaScript
react
hooks
interview-prep
error-handling
By @ethandubois
April 28, 2026
·
Updated July 24, 2026
1,053 views
27
4.2 (15)
PR review: the author wrapped Count in React.memo because the profiler showed it re-rendering on every click. The memo did nothing. Find the bug and fix it.
The diff that landed
The child is memo-wrapped but still re-renders on every increment. The parent passes a fresh arrow function on every render as onIncrement.
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