自定义Hooks设计模式

1. 设计原则

• 以 use 开头
• 只在函数组件或自定义 Hook 中调用
• 封装可复用的有状态逻辑

2. 常见模式

// useToggle
function useToggle(initial = false) {
  const [value, setValue] = useState(initial);
  const toggle = useCallback(() => setValue((v) => !v), []);
  return [value, toggle];
}

// useDebounce
function useDebounce(value, delay) {
  const [debouncedValue, setDebouncedValue] = useState(value);
  useEffect(() => {
    const timer = setTimeout(() => setDebouncedValue(value), delay);
    return () => clearTimeout(timer);
  }, [value, delay]);
  return debouncedValue;
}

// useLocalStorage
function useLocalStorage(key, initialValue) {
  const [value, setValue] = useState(() => {
    const stored = localStorage.getItem(key);
    return stored ? JSON.parse(stored) : initialValue;
  });
  useEffect(() => {
    localStorage.setItem(key, JSON.stringify(value));
  }, [key, value]);
  return [value, setValue];
}

// useFetch
function useFetch(url) {
  const [data, setData] = useState(null);
  const [error, setError] = useState(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    const controller = new AbortController();
    fetch(url, { signal: controller.signal })
      .then((r) => r.json())
      .then(setData)
      .catch(setError)
      .finally(() => setLoading(false));
    return () => controller.abort();
  }, [url]);

  return { data, error, loading };
}