Handling 'Race Conditions' in Async Watchers

Race conditions occur when an older async request resolves after a newer one; use the onCleanup callback in watch to cancel stale requests.

When watching an ID and fetching data, if the ID changes rapidly (ID 1 -> ID 2), the fetch for ID 1 might finish after ID 2. Vue's watch and watchEffect provide a third argument onCleanup. You can use this to set a flag or abort an AbortController so that only the most recent request's result is applied to the state.