What happens if I miss a dependency in useEffect?
The effect uses a stale version of that value and does not react when it changes. This causes bugs that are hard to trace because the code looks correct but behaves wrong. The hooks lint plugin catches these.
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More FAQs in useEffect Dependency Array Mistakes That Cause Infinite Loops
Usually because you forgot the dependency array, or because you included a state variable that you update inside the effect. Each update triggers another render and another run. Fix the array so the effect only runs when intended.
Because you included an object or function that is recreated on every render. The reference changes each time, so the effect runs every render. Memoize the value or move it inside the effect.
Use an empty dependency array. This tells React to run the effect only once after the initial mount and clean it up on unmount. Be sure you truly mean mount-only and are not skipping a real dependency.
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