Advanced Use Latest

---
name: advanced-use-latest
description: useLatest for Stable Callback Refs. Use when you need help with advanced use latest.
license: CC-BY-NC-SA-4.0
metadata:
  risk: unknown
  source: community
  kind: mode
  category: rules
---

## useLatest for Stable Callback Refs

Access latest values in callbacks without adding them to dependency arrays. Prevents effect re-runs while avoiding stale closures.

**Implementation:**

```typescript
function useLatest<T>(value: T) {
  const ref = useRef(value);
  useEffect(() => {
    ref.current = value;
  }, [value]);
  return ref;
}
```

**Incorrect (effect re-runs on every callback change):**

```tsx
function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
  const [query, setQuery] = useState("");

  useEffect(() => {
    const timeout = setTimeout(() => onSearch(query), 300);
    return () => clearTimeout(timeout);
  }, [query, onSearch]);
}
```

**Correct (stable effect, fresh callback):**

```tsx
function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
  const [query, setQuery] = useState("");
  const onSearchRef = useLatest(onSearch);

  useEffect(() => {
    const timeout = setTimeout(() => onSearchRef.current(query), 300);
    return () => clearTimeout(timeout);
  }, [query]);
}
```