设计与创意 · SKILL.md

state-management

state-management

【设计与创意】Implement state management patterns for frontend applications. Use when managing global state, handling complex data flows, or coordinating state across components. Handles React Context, Redux, Zustand, Recoil, and state management best practices.

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Aautohandai / community-skillsApache-2.0

技能说明

GitHub

name: state-management description: Implement state management patterns for frontend applications. Use when managing global state, handling complex data flows, or coordinating state across components. Handles React Context, Redux, Zustand, Recoil, and state management best practices. metadata: tags: state-management, React, Redux, Context, Zustand, Recoil, global-state platforms: Claude, ChatGPT, Gemini

State Management

When to use this skill

Global State Required: Multiple components share the same data
Props Drilling Problem: Passing props through 5+ levels
Complex State Logic: Authentication, shopping cart, themes, etc.
State Synchronization: Sync server data with client state

Instructions

Step 1: Determine State Scope

Distinguish between local and global state.

Decision Criteria:

Local State: Used only within a single component
- Form input values, toggle states, dropdown open/close
- Use useState, useReducer
Global State: Shared across multiple components
- User authentication, shopping cart, theme, language settings
- Use Context API, Redux, Zustand

Example:

// ✅ Local state (single component)
function SearchBox() {
  const [query, setQuery] = useState('');
  const [isOpen, setIsOpen] = useState(false);

  return (
    <div>
      <input
        value={query}
        onChange={(e) => setQuery(e.target.value)}
        onFocus={() => setIsOpen(true)}
      />
      {isOpen && <SearchResults query={query} />}
    </div>
  );
}

// ✅ Global state (multiple components)
// User authentication info is used in Header, Profile, Settings, etc.
const { user, logout } = useAuth();  // Context or Zustand

Step 2: React Context API (Simple Global State)

Suitable for lightweight global state management.

Example (Authentication Context):

// contexts/AuthContext.tsx
import { createContext, useContext, useState, ReactNode } from 'react';

interface User {
  id: string;
  email: string;
  name: string;
}

interface AuthContextType {
  user: User | null;
  login: (email: string, password: string) => Promise<void>;
  logout: () => void;
  isAuthenticated: boolean;
}

const AuthContext = createContext<AuthContextType | undefined>(undefined);

export function AuthProvider({ children }: { children: ReactNode }) {
  const [user, setUser] = useState<User | null>(null);

  const login = async (email: string, password: string) => {
    const response = await fetch('/api/auth/login', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ email, password })
    });

    const data = await response.json();
    setUser(data.user);
    localStorage.setItem('token', data.token);
  };

  const logout = () => {
    setUser(null);
    localStorage.removeItem('token');
  };

  return (
    <AuthContext.Provider value={{
      user,
      login,
      logout,
      isAuthenticated: !!user
    }}>
      {children}
    </AuthContext.Provider>
  );
}

// Custom hook
export function useAuth() {
  const context = useContext(AuthContext);
  if (!context) {
    throw new Error('useAuth must be used within AuthProvider');
  }
  return context;
}

Usage:

// App.tsx
function App() {
  return (
    <AuthProvider>
      <Router>
        <Header />
        <Routes />
      </Router>
    </AuthProvider>
  );
}

// Header.tsx
function Header() {
  const { user, logout, isAuthenticated } = useAuth();

  return (
    <header>
      {isAuthenticated ? (
        <>
          <span>Welcome, {user!.name}</span>
          <button onClick={logout}>Logout</button>
        </>
      ) : (
        <Link to="/login">Login</Link>
      )}
    </header>
  );
}

Step 3: Zustand (Modern and Concise State Management)

Simpler than Redux with less boilerplate.

Installation:

npm install zustand

Example (Shopping Cart):

// stores/cartStore.ts
import { create } from 'zustand';
import { devtools, persist } from 'zustand/middleware';

interface CartItem {
  id: string;
  name: string;
  price: number;
  quantity: number;
}

interface CartStore {
  items: CartItem[];
  addItem: (item: Omit<CartItem, 'quantity'>) => void;
  removeItem: (id: string) => void;
  updateQuantity: (id: string, quantity: number) => void;
  clearCart: () => void;
  total: () => number;
}

export const useCartStore = create<CartStore>()(
  devtools(
    persist(
      (set, get) => ({
        items: [],

        addItem: (item) => set((state) => {
          const existing = state.items.find(i => i.id === item.id);
          if (existing) {
            return {
              items: state.items.map(i =>
                i.id === item.id
                  ? { ...i, quantity: i.quantity + 1 }
                  : i
              )
            };
          }
          return { items: [...state.items, { ...item, quantity: 1 }] };
        }),

        removeItem: (id) => set((state) => ({
          items: state.items.filter(item => item.id !== id)
        })),

        updateQuantity: (id, quantity) => set((state) => ({
          items: state.items.map(item =>
            item.id === id ? { ...item, quantity } : item
          )
        })),

        clearCart: () => set({ items: [] }),

        total: () => {
          const { items } = get();
          return items.reduce((sum, item) => sum + item.price * item.quantity, 0);
        }
      }),
      { name: 'cart-storage' }  // localStorage key
    )
  )
);

Usage:

// components/ProductCard.tsx
function ProductCard({ product }) {
  const addItem = useCartStore(state => state.addItem);

  return (
    <div>
      <h3>{product.name}</h3>
      <p>${product.price}</p>
      <button onClick={() => addItem(product)}>
        Add to Cart
      </button>
    </div>
  );
}

// components/Cart.tsx
function Cart() {
  const items = useCartStore(state => state.items);
  const total = useCartStore(state => state.total());
  const removeItem = useCartStore(state => state.removeItem);

  return (
    <div>
      <h2>Cart</h2>
      {items.map(item => (
        <div key={item.id}>
          <span>{item.name} x {item.quantity}</span>
          <span>${item.price * item.quantity}</span>
          <button onClick={() => removeItem(item.id)}>Remove</button>
        </div>
      ))}
      <p>Total: ${total.toFixed(2)}</p>
    </div>
  );
}

Step 4: Redux Toolkit (Large-Scale Apps)

Use when complex state logic and middleware are required.

Installation:

npm install @reduxjs/toolkit react-redux

Example (Todo):

// store/todosSlice.ts
import { createSlice, createAsyncThunk, PayloadAction } from '@reduxjs/toolkit';

interface Todo {
  id: string;
  text: string;
  completed: boolean;
}

interface TodosState {
  items: Todo[];
  status: 'idle' | 'loading' | 'failed';
}

const initialState: TodosState = {
  items: [],
  status: 'idle'
};

// Async action
export const fetchTodos = createAsyncThunk('todos/fetch', async () => {
  const response = await fetch('/api/todos');
  return response.json();
});

const todosSlice = createSlice({
  name: 'todos',
  initialState,
  reducers: {
    addTodo: (state, action: PayloadAction<string>) => {
      state.items.push({
        id: Date.now().toString(),
        text: action.payload,
        completed: false
      });
    },
    toggleTodo: (state, action: PayloadAction<string>) => {
      const todo = state.items.find(t => t.id === action.payload);
      if (todo) {
        todo.completed = !todo.completed;
      }
    },
    removeTodo: (state, action: PayloadAction<string>) => {
      state.items = state.items.filter(t => t.id !== action.payload);
    }
  },
  extraReducers: (builder) => {
    builder
      .addCase(fetchTodos.pending, (state) => {
        state.status = 'loading';
      })
      .addCase(fetchTodos.fulfilled, (state, action) => {
        state.status = 'idle';
        state.items = action.payload;
      })
      .addCase(fetchTodos.rejected, (state) => {
        state.status = 'failed';
      });
  }
});

export const { addTodo, toggleTodo, removeTodo } = todosSlice.actions;
export default todosSlice.reducer;

// store/index.ts
import { configureStore } from '@reduxjs/toolkit';
import todosReducer from './todosSlice';

export const store = configureStore({
  reducer: {
    todos: todosReducer
  }
});

export type RootState = ReturnType<typeof store.getState>;
export type AppDispatch = typeof store.dispatch;

Usage:

// App.tsx
import { Provider } from 'react-redux';
import { store } from './store';

function App() {
  return (
    <Provider store={store}>
      <TodoApp />
    </Provider>
  );
}

// components/TodoList.tsx
import { useSelector, useDispatch } from 'react-redux';
import { RootState } from '../store';
import { toggleTodo, removeTodo } from '../store/todosSlice';

function TodoList() {
  const todos = useSelector((state: RootState) => state.todos.items);
  const dispatch = useDispatch();

  return (
    <ul>
      {todos.map(todo => (
        <li key={todo.id}>
          <input
            type="checkbox"
            checked={todo.completed}
            onChange={() => dispatch(toggleTodo(todo.id))}
          />
          <span style={{ textDecoration: todo.completed ? 'line-through' : 'none' }}>
            {todo.text}
          </span>
          <button onClick={() => dispatch(removeTodo(todo.id))}>Delete</button>
        </li>
      ))}
    </ul>
  );
}

Step 5: Server State Management (React Query / TanStack Query)

Specialized for API data fetching and caching.

import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';

function UserProfile({ userId }: { userId: string }) {
  const queryClient = useQueryClient();

  // GET: Fetch user info
  const { data: user, isLoading, error } = useQuery({
    queryKey: ['user', userId],
    queryFn: async () => {
      const res = await fetch(`/api/users/${userId}`);
      return res.json();
    },
    staleTime: 5 * 60 * 1000,  // Cache for 5 minutes
  });

  // POST: Update user info
  const mutation = useMutation({
    mutationFn: async (updatedUser: Partial<User>) => {
      const res = await fetch(`/api/users/${userId}`, {
        method: 'PATCH',
        body: JSON.stringify(updatedUser)
      });
      return res.json();
    },
    onSuccess: () => {
      // Invalidate cache and refetch
      queryClient.invalidateQueries({ queryKey: ['user', userId] });
    }
  });

  if (isLoading) return <div>Loading...</div>;
  if (error) return <div>Error: {error.message}</div>;

  return (
    <div>
      <h2>{user.name}</h2>
      <p>{user.email}</p>
      <button onClick={() => mutation.mutate({ name: 'New Name' })}>
        Update Name
      </button>
    </div>
  );
}

Output format