# React Hooks Reference

Advanced custom hooks and patterns.

## References

- [**Custom Hooks Library**](custom-hooks.md) - Common custom hook implementations.
- [**Advanced Patterns**](advanced-patterns.md) - Complex hook compositions.

## Custom Hooks Library

```jsx
// useLocalStorage - Persist state in localStorage
function useLocalStorage(key, initialValue) {
  const [storedValue, setStoredValue] = useState(() => {
    try {
      const item = window.localStorage.getItem(key);
      return item ? JSON.parse(item) : initialValue;
    } catch (error) {
      console.error(error);
      return initialValue;
    }
  });

  const setValue = (value) => {
    try {
      const valueToStore = value instanceof Function ? value(storedValue) : value;
      setStoredValue(valueToStore);
      window.localStorage.setItem(key, JSON.stringify(valueToStore));
    } catch (error) {
      console.error(error);
    }
  };

  return [storedValue, setValue];
}

// useDebounce - Debounce a value
function useDebounce(value, delay) {
  const [debouncedValue, setDebouncedValue] = useState(value);

  useEffect(() => {
    const handler = setTimeout(() => setDebouncedValue(value), delay);
    return () => clearTimeout(handler);
  }, [value, delay]);

  return debouncedValue;
}

// useWindowSize - Track window dimensions
function useWindowSize() {
  const [size, setSize] = useState({
    width: window.innerWidth,
    height: window.innerHeight,
  });

  useEffect(() => {
    const handleResize = () => {
      setSize({
        width: window.innerWidth,
        height: window.innerHeight,
      });
    };

    window.addEventListener('resize', handleResize);
    return () => window.removeEventListener('resize', handleResize);
  }, []);

  return size;
}

// useOnClickOutside - Detect clicks outside an element
function useOnClickOutside(ref, handler) {
  useEffect(() => {
    const listener = (event) => {
      if (!ref.current || ref.current.contains(event.target)) {
        return;
      }
      handler(event);
    };

    document.addEventListener('mousedown', listener);
    document.addEventListener('touchstart', listener);

    return () => {
      document.removeEventListener('mousedown', listener);
      document.removeEventListener('touchstart', listener);
    };
  }, [ref, handler]);
}

// useIntersectionObserver - Detect element visibility
function useIntersectionObserver(ref, options) {
  const [isIntersecting, setIsIntersecting] = useState(false);

  useEffect(() => {
    const observer = new IntersectionObserver(([entry]) => {
      setIsIntersecting(entry.isIntersecting);
    }, options);

    if (ref.current) {
      observer.observe(ref.current);
    }

    return () => observer.disconnect();
  }, [ref, options]);

  return isIntersecting;
}

// usePrevious - Get previous value
function usePrevious(value) {
  const ref = useRef();

  useEffect(() => {
    ref.current = value;
  }, [value]);

  return ref.current;
}

// useToggle - Boolean toggle
function useToggle(initialValue = false) {
  const [value, setValue] = useState(initialValue);

  const toggle = useCallback(() => {
    setValue(v => !v);
  }, []);

  return [value, toggle];
}
```
