Explain useEffect dependency array behavior for [], [deps], and omitted
It tests reactive dependency tracking. Omitting re-runs every render; [] runs on mount with cleanup on unmount; [deps] re-runs when Object.is detects change. Red flag: claiming [] means 'run once' without mentioning cleanup or stale values.
It tests whether you understand how React schedules Effect re-execution based on reactive values. Omitting the array causes the Effect to run after every commit; [] limits it to mount and triggers cleanup on unmount; [prop1, state2] re-runs only when Object.is detects a change. A strong answer notes that [] still runs cleanup on unmount and may re-run in Strict Mode. Red flag: describing [] as 'run once' while ignoring cleanup, stale closures, or the linter rule.
Read the original → react.dev
- #react
- #hooks
- #useeffect
- #dependencies
- #interview
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