📦 deps(thirdparty): update snapshots

2026-05-29 08:33:53 +00:00
parent fdb52f1e96
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+# Hook TypeScript Patterns
+
+Type-safe hook patterns for useState, useRef, useReducer, useContext, and custom hooks.
+
+## useState
+
+Type inference works for simple types; explicit typing needed for unions/null.
+
+```typescript
+// Inference works
+const [count, setCount] = useState(0); // number
+const [name, setName] = useState(''); // string
+const [items, setItems] = useState<string[]>([]); // explicit for empty arrays
+
+// Explicit for unions/null
+const [user, setUser] = useState<User | null>(null);
+const [status, setStatus] = useState<'idle' | 'loading' | 'success'>('idle');
+
+// Complex initial state
+type FormData = { name: string; email: string };
+const [formData, setFormData] = useState<FormData>({
+  name: '',
+  email: '',
+});
+
+// Lazy initialization
+const [data, setData] = useState<Data>(() => {
+  const cached = localStorage.getItem('data');
+  return cached ? JSON.parse(cached) : defaultData;
+});
+```
+
+## useRef
+
+Distinguish DOM refs (null initial) from mutable value refs (value initial).
+
+```typescript
+// DOM element ref - null initial, readonly .current
+const inputRef = useRef<HTMLInputElement>(null);
+const buttonRef = useRef<HTMLButtonElement>(null);
+const divRef = useRef<HTMLDivElement>(null);
+
+useEffect(() => {
+  inputRef.current?.focus(); // Optional chaining for null
+}, []);
+
+// Mutable value ref - non-null initial, mutable .current
+const countRef = useRef<number>(0);
+countRef.current += 1; // No optional chaining
+
+const previousValueRef = useRef<string | undefined>(undefined);
+previousValueRef.current = currentValue;
+
+// Interval/timeout ref
+const timeoutRef = useRef<ReturnType<typeof setTimeout>>();
+const intervalRef = useRef<ReturnType<typeof setInterval>>();
+
+useEffect(() => {
+  timeoutRef.current = setTimeout(() => {}, 1000);
+  return () => {
+    if (timeoutRef.current) clearTimeout(timeoutRef.current);
+  };
+}, []);
+
+// Callback ref for dynamic elements
+const callbackRef = useCallback((node: HTMLDivElement | null) => {
+  if (node) {
+    node.scrollIntoView({ behavior: 'smooth' });
+  }
+}, []);
+```
+
+## useReducer
+
+Typed actions with discriminated unions.
+
+```typescript
+type State = {
+  count: number;
+  status: 'idle' | 'loading' | 'success' | 'error';
+  error?: string;
+};
+
+type Action =
+  | { type: 'increment' }
+  | { type: 'decrement' }
+  | { type: 'set'; payload: number }
+  | { type: 'setStatus'; payload: State['status'] }
+  | { type: 'setError'; payload: string };
+
+function reducer(state: State, action: Action): State {
+  switch (action.type) {
+    case 'increment':
+      return { ...state, count: state.count + 1 };
+    case 'decrement':
+      return { ...state, count: state.count - 1 };
+    case 'set':
+      return { ...state, count: action.payload };
+    case 'setStatus':
+      return { ...state, status: action.payload };
+    case 'setError':
+      return { ...state, status: 'error', error: action.payload };
+    default:
+      return state;
+  }
+}
+
+function Component() {
+  const [state, dispatch] = useReducer(reducer, {
+    count: 0,
+    status: 'idle',
+  });
+
+  dispatch({ type: 'set', payload: 10 }); // Type-safe
+  dispatch({ type: 'set' }); // Error: payload required
+  dispatch({ type: 'unknown' }); // Error: invalid action type
+}
+```
+
+### Reducer with Context
+
+```typescript
+type AuthState = {
+  user: User | null;
+  isAuthenticated: boolean;
+};
+
+type AuthAction =
+  | { type: 'login'; payload: User }
+  | { type: 'logout' };
+
+type AuthContextValue = {
+  state: AuthState;
+  dispatch: React.Dispatch<AuthAction>;
+};
+
+const AuthContext = createContext<AuthContextValue | null>(null);
+
+function authReducer(state: AuthState, action: AuthAction): AuthState {
+  switch (action.type) {
+    case 'login':
+      return { user: action.payload, isAuthenticated: true };
+    case 'logout':
+      return { user: null, isAuthenticated: false };
+  }
+}
+
+function AuthProvider({ children }: { children: React.ReactNode }) {
+  const [state, dispatch] = useReducer(authReducer, {
+    user: null,
+    isAuthenticated: false,
+  });
+
+  return (
+    <AuthContext.Provider value={{ state, dispatch }}>
+      {children}
+    </AuthContext.Provider>
+  );
+}
+
+function useAuth() {
+  const context = useContext(AuthContext);
+  if (!context) throw new Error('useAuth must be used within AuthProvider');
+  return context;
+}
+```
+
+## useContext
+
+Typed context with and without default values.
+
+```typescript
+// Context with default value
+type Theme = 'light' | 'dark';
+const ThemeContext = createContext<Theme>('light');
+
+function useTheme() {
+  return useContext(ThemeContext); // Always Theme, never null
+}
+
+// Context without default (must handle null)
+type User = { id: string; name: string };
+const UserContext = createContext<User | null>(null);
+
+function useUser() {
+  const user = useContext(UserContext);
+  if (!user) throw new Error('useUser must be used within UserProvider');
+  return user; // Type narrowed to User
+}
+
+// Context with complex value
+type AppContextValue = {
+  theme: Theme;
+  user: User | null;
+  setTheme: (theme: Theme) => void;
+  login: (user: User) => void;
+  logout: () => void;
+};
+
+const AppContext = createContext<AppContextValue | null>(null);
+
+function useApp() {
+  const context = useContext(AppContext);
+  if (!context) throw new Error('useApp must be used within AppProvider');
+  return context;
+}
+```
+
+## Custom Hooks
+
+Return type patterns for simple and complex hooks.
+
+```typescript
+// Object return - properties accessed by name
+function useCounter(initial: number) {
+  const [count, setCount] = useState(initial);
+  const increment = () => setCount((c) => c + 1);
+  const decrement = () => setCount((c) => c - 1);
+  const reset = () => setCount(initial);
+
+  return { count, increment, decrement, reset };
+}
+
+// Usage
+const { count, increment } = useCounter(0);
+
+// Tuple return - positional destructuring
+function useToggle(initial = false): [boolean, () => void, () => void, () => void] {
+  const [value, setValue] = useState(initial);
+  const toggle = () => setValue((v) => !v);
+  const setTrue = () => setValue(true);
+  const setFalse = () => setValue(false);
+
+  return [value, toggle, setTrue, setFalse];
+}
+
+// Usage
+const [isOpen, toggleOpen, open, close] = useToggle();
+
+// as const for tuple inference
+function useLocalStorage<T>(key: string, initial: T) {
+  const [value, setValue] = useState<T>(() => {
+    const stored = localStorage.getItem(key);
+    return stored ? JSON.parse(stored) : initial;
+  });
+
+  useEffect(() => {
+    localStorage.setItem(key, JSON.stringify(value));
+  }, [key, value]);
+
+  return [value, setValue] as const; // readonly tuple
+}
+
+// Generic custom hook
+function useFetch<T>(url: string) {
+  const [data, setData] = useState<T | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<Error | null>(null);
+
+  useEffect(() => {
+    let cancelled = false;
+
+    fetch(url)
+      .then((res) => res.json())
+      .then((json: T) => {
+        if (!cancelled) {
+          setData(json);
+          setLoading(false);
+        }
+      })
+      .catch((err) => {
+        if (!cancelled) {
+          setError(err);
+          setLoading(false);
+        }
+      });
+
+    return () => {
+      cancelled = true;
+    };
+  }, [url]);
+
+  return { data, loading, error };
+}
+
+// Usage - T inferred from usage or explicit
+const { data } = useFetch<User[]>('/api/users');
+```
+
+## useCallback and useMemo
+
+Typed callbacks and memoized values.
+
+```typescript
+// useCallback with typed parameters
+const handleClick = useCallback((id: string, event: React.MouseEvent) => {
+  console.log(id, event.target);
+}, []);
+
+// useCallback returning value
+const formatDate = useCallback((date: Date): string => {
+  return date.toLocaleDateString();
+}, []);
+
+// useMemo with explicit return type
+const sortedItems = useMemo((): Item[] => {
+  return [...items].sort((a, b) => a.name.localeCompare(b.name));
+}, [items]);
+
+// useMemo with complex computation
+const stats = useMemo(() => {
+  return {
+    total: items.length,
+    average: items.reduce((a, b) => a + b.value, 0) / items.length,
+    max: Math.max(...items.map((i) => i.value)),
+  };
+}, [items]);
+```
+
+## useImperativeHandle
+
+Expose imperative methods from components.
+
+```typescript
+type InputHandle = {
+  focus: () => void;
+  clear: () => void;
+  getValue: () => string;
+};
+
+type InputProps = {
+  ref?: React.Ref<InputHandle>;
+  label: string;
+};
+
+function CustomInput({ ref, label }: InputProps) {
+  const inputRef = useRef<HTMLInputElement>(null);
+
+  useImperativeHandle(ref, () => ({
+    focus: () => inputRef.current?.focus(),
+    clear: () => {
+      if (inputRef.current) inputRef.current.value = '';
+    },
+    getValue: () => inputRef.current?.value ?? '',
+  }));
+
+  return (
+    <div>
+      <label>{label}</label>
+      <input ref={inputRef} />
+    </div>
+  );
+}
+
+// Usage
+function Form() {
+  const inputRef = useRef<InputHandle>(null);
+
+  const handleSubmit = () => {
+    const value = inputRef.current?.getValue();
+    inputRef.current?.clear();
+  };
+
+  return (
+    <form>
+      <CustomInput ref={inputRef} label="Name" />
+      <button onClick={() => inputRef.current?.focus()}>Focus</button>
+    </form>
+  );
+}
+```
+
+## useLayoutEffect
+
+Same signature as useEffect, runs synchronously after DOM mutations.
+
+```typescript
+function Tooltip({ targetRef }: { targetRef: React.RefObject<HTMLElement> }) {
+  const tooltipRef = useRef<HTMLDivElement>(null);
+  const [position, setPosition] = useState({ top: 0, left: 0 });
+
+  useLayoutEffect(() => {
+    if (targetRef.current && tooltipRef.current) {
+      const rect = targetRef.current.getBoundingClientRect();
+      setPosition({
+        top: rect.bottom + 8,
+        left: rect.left,
+      });
+    }
+  }, [targetRef]);
+
+  return (
+    <div
+      ref={tooltipRef}
+      style={{ position: 'fixed', top: position.top, left: position.left }}
+    >
+      Tooltip content
+    </div>
+  );
+}
+```
+
+## useId
+
+Generate unique IDs for accessibility.
+
+```typescript
+function FormField({ label }: { label: string }) {
+  const id = useId();
+  const errorId = useId();
+
+  return (
+    <div>
+      <label htmlFor={id}>{label}</label>
+      <input id={id} aria-describedby={errorId} />
+      <span id={errorId}>Error message</span>
+    </div>
+  );
+}
+```
+
+## useSyncExternalStore
+
+Subscribe to external stores with SSR support.
+
+```typescript
+type Store<T> = {
+  getState: () => T;
+  subscribe: (callback: () => void) => () => void;
+};
+
+function useStore<T>(store: Store<T>): T {
+  return useSyncExternalStore(
+    store.subscribe,
+    store.getState,
+    store.getState // Server snapshot
+  );
+}
+
+// Example: window width store
+const widthStore: Store<number> = {
+  getState: () => (typeof window !== 'undefined' ? window.innerWidth : 0),
+  subscribe: (callback) => {
+    window.addEventListener('resize', callback);
+    return () => window.removeEventListener('resize', callback);
+  },
+};
+
+function useWindowWidth() {
+  return useSyncExternalStore(
+    widthStore.subscribe,
+    widthStore.getState,
+    () => 0 // Server fallback
+  );
+}
+```