---

name: zustand-state-builder description: Implements lightweight state management using Zustand with TypeScript, persistence, devtools, and modular store patterns. Use when users request "zustand store", "state management", "global state", "zustand setup", or "jotai alternative".

Zustand State Builder

Build lightweight, scalable state management with Zustand's minimal API.

Core Workflow

1. Identify state needs: Determine what needs global state
2. Create store: Define state shape and actions
3. Add TypeScript types: Full type safety
4. Enable middleware: Devtools, persist, immer
5. Split stores: Modular slices for large apps
6. Connect components: Use hooks to access state

Installation

Copynpm install zustand

# Optional middleware
npm install immer  # For immutable updates

Basic Store

Simple Counter Store

Copy// stores/counter.ts
import { create } from 'zustand';

interface CounterState {
  count: number;
  increment: () => void;
  decrement: () => void;
  reset: () => void;
  incrementBy: (amount: number) => void;
}

export const useCounterStore = create<CounterState>((set) => ({
  count: 0,
  increment: () => set((state) => ({ count: state.count + 1 })),
  decrement: () => set((state) => ({ count: state.count - 1 })),
  reset: () => set({ count: 0 }),
  incrementBy: (amount) => set((state) => ({ count: state.count + amount })),
}));

// Usage in component
function Counter() {
  const { count, increment, decrement } = useCounterStore();

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={increment}>+</button>
      <button onClick={decrement}>-</button>
    </div>
  );
}

Async Actions

Copy// stores/users.ts
import { create } from 'zustand';

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

interface UsersState {
  users: User[];
  isLoading: boolean;
  error: string | null;
  fetchUsers: () => Promise<void>;
  addUser: (user: Omit<User, 'id'>) => Promise<void>;
  deleteUser: (id: string) => Promise<void>;
}

export const useUsersStore = create<UsersState>((set, get) => ({
  users: [],
  isLoading: false,
  error: null,

  fetchUsers: async () => {
    set({ isLoading: true, error: null });
    try {
      const response = await fetch('/api/users');
      const users = await response.json();
      set({ users, isLoading: false });
    } catch (error) {
      set({ error: 'Failed to fetch users', isLoading: false });
    }
  },

  addUser: async (userData) => {
    set({ isLoading: true, error: null });
    try {
      const response = await fetch('/api/users', {
        method: 'POST',
        body: JSON.stringify(userData),
      });
      const newUser = await response.json();
      set((state) => ({
        users: [...state.users, newUser],
        isLoading: false,
      }));
    } catch (error) {
      set({ error: 'Failed to add user', isLoading: false });
    }
  },

  deleteUser: async (id) => {
    const previousUsers = get().users;
    // Optimistic update
    set((state) => ({
      users: state.users.filter((u) => u.id !== id),
    }));
    try {
      await fetch(`/api/users/${id}`, { method: 'DELETE' });
    } catch (error) {
      // Rollback on error
      set({ users: previousUsers, error: 'Failed to delete user' });
    }
  },
}));

Middleware

DevTools Integration

Copyimport { create } from 'zustand';
import { devtools } from 'zustand/middleware';

interface StoreState {
  count: number;
  increment: () => void;
}

export const useStore = create<StoreState>()(
  devtools(
    (set) => ({
      count: 0,
      increment: () =>
        set(
          (state) => ({ count: state.count + 1 }),
          false,
          'increment' // Action name for devtools
        ),
    }),
    { name: 'CounterStore' } // Store name in devtools
  )
);

Persistence

Copyimport { create } from 'zustand';
import { persist, createJSONStorage } from 'zustand/middleware';

interface SettingsState {
  theme: 'light' | 'dark';
  language: string;
  notifications: boolean;
  setTheme: (theme: 'light' | 'dark') => void;
  setLanguage: (language: string) => void;
  toggleNotifications: () => void;
}

export const useSettingsStore = create<SettingsState>()(
  persist(
    (set) => ({
      theme: 'light',
      language: 'en',
      notifications: true,
      setTheme: (theme) => set({ theme }),
      setLanguage: (language) => set({ language }),
      toggleNotifications: () =>
        set((state) => ({ notifications: !state.notifications })),
    }),
    {
      name: 'settings-storage', // localStorage key
      storage: createJSONStorage(() => localStorage),
      partialize: (state) => ({
        // Only persist these fields
        theme: state.theme,
        language: state.language,
        notifications: state.notifications,
      }),
    }
  )
);

Immer Middleware

Copyimport { create } from 'zustand';
import { immer } from 'zustand/middleware/immer';

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

interface TodosState {
  todos: Todo[];
  addTodo: (text: string) => void;
  toggleTodo: (id: string) => void;
  updateTodo: (id: string, text: string) => void;
  deleteTodo: (id: string) => void;
}

export const useTodosStore = create<TodosState>()(
  immer((set) => ({
    todos: [],

    addTodo: (text) =>
      set((state) => {
        state.todos.push({
          id: crypto.randomUUID(),
          text,
          completed: false,
        });
      }),

    toggleTodo: (id) =>
      set((state) => {
        const todo = state.todos.find((t) => t.id === id);
        if (todo) {
          todo.completed = !todo.completed;
        }
      }),

    updateTodo: (id, text) =>
      set((state) => {
        const todo = state.todos.find((t) => t.id === id);
        if (todo) {
          todo.text = text;
        }
      }),

    deleteTodo: (id) =>
      set((state) => {
        const index = state.todos.findIndex((t) => t.id === id);
        if (index !== -1) {
          state.todos.splice(index, 1);
        }
      }),
  }))
);

Combined Middleware

Copyimport { create } from 'zustand';
import { devtools, persist } from 'zustand/middleware';
import { immer } from 'zustand/middleware/immer';

export const useStore = create<StoreState>()(
  devtools(
    persist(
      immer((set) => ({
        // ... state and actions
      })),
      { name: 'store' }
    ),
    { name: 'MyStore' }
  )
);

Slices Pattern

Modular Store Architecture

Copy// stores/slices/authSlice.ts
import { StateCreator } from 'zustand';

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

export const createAuthSlice: StateCreator<
  AuthSlice & CartSlice, // Combined state type
  [],
  [],
  AuthSlice
> = (set) => ({
  user: null,
  isAuthenticated: false,

  login: async (email, password) => {
    const response = await fetch('/api/auth/login', {
      method: 'POST',
      body: JSON.stringify({ email, password }),
    });
    const user = await response.json();
    set({ user, isAuthenticated: true });
  },

  logout: () => set({ user: null, isAuthenticated: false }),
});

Copy// stores/slices/cartSlice.ts
import { StateCreator } from 'zustand';

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

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

export const createCartSlice: StateCreator<
  AuthSlice & CartSlice,
  [],
  [],
  CartSlice
> = (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((i) => i.id !== id),
    })),

  updateQuantity: (id, quantity) =>
    set((state) => ({
      items:
        quantity <= 0
          ? state.items.filter((i) => i.id !== id)
          : state.items.map((i) => (i.id === id ? { ...i, quantity } : i)),
    })),

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

  totalItems: () => get().items.reduce((sum, i) => sum + i.quantity, 0),

  totalPrice: () =>
    get().items.reduce((sum, i) => sum + i.price * i.quantity, 0),
});

Copy// stores/index.ts
import { create } from 'zustand';
import { devtools, persist } from 'zustand/middleware';
import { createAuthSlice, AuthSlice } from './slices/authSlice';
import { createCartSlice, CartSlice } from './slices/cartSlice';

type StoreState = AuthSlice & CartSlice;

export const useStore = create<StoreState>()(
  devtools(
    persist(
      (...args) => ({
        ...createAuthSlice(...args),
        ...createCartSlice(...args),
      }),
      {
        name: 'app-store',
        partialize: (state) => ({
          items: state.items, // Persist cart
          // Don't persist auth (handle with tokens)
        }),
      }
    ),
    { name: 'AppStore' }
  )
);

Selectors

Optimized Selectors

Copy// Avoid re-renders with selectors
function UserName() {
  // Only re-renders when user.name changes
  const userName = useStore((state) => state.user?.name);
  return <span>{userName}</span>;
}

// Multiple values with shallow comparison
import { shallow } from 'zustand/shallow';

function UserInfo() {
  const { name, email } = useStore(
    (state) => ({ name: state.user?.name, email: state.user?.email }),
    shallow
  );
  return (
    <div>
      <p>{name}</p>
      <p>{email}</p>
    </div>
  );
}

// Computed values
function CartSummary() {
  const totalItems = useStore((state) =>
    state.items.reduce((sum, i) => sum + i.quantity, 0)
  );
  const totalPrice = useStore((state) =>
    state.items.reduce((sum, i) => sum + i.price * i.quantity, 0)
  );

  return (
    <div>
      <p>Items: {totalItems}</p>
      <p>Total: ${totalPrice.toFixed(2)}</p>
    </div>
  );
}

Reusable Selector Hooks

Copy// stores/selectors.ts
import { useStore } from './index';
import { shallow } from 'zustand/shallow';

// Auth selectors
export const useAuth = () =>
  useStore(
    (state) => ({
      user: state.user,
      isAuthenticated: state.isAuthenticated,
      login: state.login,
      logout: state.logout,
    }),
    shallow
  );

export const useUser = () => useStore((state) => state.user);
export const useIsAuthenticated = () => useStore((state) => state.isAuthenticated);

// Cart selectors
export const useCart = () =>
  useStore(
    (state) => ({
      items: state.items,
      addItem: state.addItem,
      removeItem: state.removeItem,
      updateQuantity: state.updateQuantity,
      clearCart: state.clearCart,
    }),
    shallow
  );

export const useCartTotal = () =>
  useStore((state) => ({
    items: state.items.reduce((sum, i) => sum + i.quantity, 0),
    price: state.items.reduce((sum, i) => sum + i.price * i.quantity, 0),
  }), shallow);

Outside React Usage

Copy// Access store outside React components
const { getState, setState, subscribe } = useStore;

// Get current state
const currentUser = useStore.getState().user;

// Update state
useStore.setState({ user: newUser });

// Subscribe to changes
const unsubscribe = useStore.subscribe((state) => {
  console.log('State changed:', state);
});

// Subscribe to specific slice
const unsubscribeCart = useStore.subscribe(
  (state) => state.items,
  (items, previousItems) => {
    console.log('Cart changed:', items);
  }
);

Server State Integration

With TanStack Query

Copy// stores/ui.ts - Client state only
import { create } from 'zustand';

interface UIState {
  sidebarOpen: boolean;
  modalOpen: boolean;
  toggleSidebar: () => void;
  openModal: () => void;
  closeModal: () => void;
}

export const useUIStore = create<UIState>((set) => ({
  sidebarOpen: true,
  modalOpen: false,
  toggleSidebar: () => set((s) => ({ sidebarOpen: !s.sidebarOpen })),
  openModal: () => set({ modalOpen: true }),
  closeModal: () => set({ modalOpen: false }),
}));

// hooks/useUsers.ts - Server state with TanStack Query
import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';

export function useUsers() {
  return useQuery({
    queryKey: ['users'],
    queryFn: () => fetch('/api/users').then((r) => r.json()),
  });
}

export function useCreateUser() {
  const queryClient = useQueryClient();

  return useMutation({
    mutationFn: (user: CreateUserDto) =>
      fetch('/api/users', {
        method: 'POST',
        body: JSON.stringify(user),
      }).then((r) => r.json()),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['users'] });
    },
  });
}

Testing

Copy// stores/__tests__/counter.test.ts
import { act, renderHook } from '@testing-library/react';
import { useCounterStore } from '../counter';

describe('Counter Store', () => {
  beforeEach(() => {
    // Reset store before each test
    useCounterStore.setState({ count: 0 });
  });

  it('increments count', () => {
    const { result } = renderHook(() => useCounterStore());

    act(() => {
      result.current.increment();
    });

    expect(result.current.count).toBe(1);
  });

  it('decrements count', () => {
    useCounterStore.setState({ count: 5 });
    const { result } = renderHook(() => useCounterStore());

    act(() => {
      result.current.decrement();
    });

    expect(result.current.count).toBe(4);
  });

  it('resets count', () => {
    useCounterStore.setState({ count: 10 });
    const { result } = renderHook(() => useCounterStore());

    act(() => {
      result.current.reset();
    });

    expect(result.current.count).toBe(0);
  });
});

Best Practices

1. Keep stores small: One store per domain
2. Use selectors: Prevent unnecessary re-renders
3. Separate client/server state: Use TanStack Query for server state
4. Enable devtools: Essential for debugging
5. Type everything: Full TypeScript coverage
6. Use immer for nested state: Cleaner immutable updates
7. Persist sparingly: Only persist what's needed
8. Test stores: Unit test actions and state changes

Output Checklist

Every Zustand store should include:

• TypeScript interfaces for state and actions
• Devtools middleware enabled
• Persistence where needed
• Selectors for optimized re-renders
• Slices pattern for large stores
• Async action error handling
• Outside React access method
• Unit tests for actions
• Integration with server state library