Zustand State Management

Zustand State Management

Status: Production Ready ✅ Last Updated: 2025-10-24 Latest Version: [email protected] Dependencies: React 18+, TypeScript 5+

---

Quick Start (3 Minutes)

1. Install Zustand

npm install zustand
# or
pnpm add zustand
# or
yarn add zustand

Why Zustand?

• Minimal API: Only 1 function to learn (create)
• No boilerplate: No providers, reducers, or actions
• TypeScript-first: Excellent type inference
• Fast: Fine-grained subscriptions prevent unnecessary re-renders
• Flexible: Middleware for persistence, devtools, and more

2. Create Your First Store (TypeScript)

import { create } from 'zustand'

interface BearStore {
  bears: number
  increase: (by: number) => void
  reset: () => void
}

const useBearStore = create<BearStore>()((set) => ({
  bears: 0,
  increase: (by) => set((state) => ({ bears: state.bears + by })),
  reset: () => set({ bears: 0 }),
}))

CRITICAL: Notice the double parentheses create<T>()() - this is required for TypeScript with middleware.

3. Use Store in Components

import { useBearStore } from './​store'

function BearCounter() {
  const bears = useBearStore((state) => state.bears)
  return <h1>{bears} around here...</​h1>
}

function Controls() {
  const increase = useBearStore((state) => state.increase)
  return <button onClick={() => increase(1)}>Add bear</​button>
}

Why this works:

• Components only re-render when their selected state changes
• No Context providers needed
• Selector function extracts specific state slice

---

The 3-Pattern Setup Process

Pattern 1: Basic Store (JavaScript)

For simple use cases without TypeScript:

import { create } from 'zustand'

const useStore = create((set) => ({
  count: 0,
  increment: () => set((state) => ({ count: state.count + 1 })),
  decrement: () => set((state) => ({ count: state.count - 1 })),
}))

When to use:

• Prototyping
• Small apps
• No TypeScript in project

Pattern 2: TypeScript Store (Recommended)

For production apps with type safety:

import { create } from 'zustand'

// Define store interface
interface CounterStore {
  count: number
  increment: () => void
  decrement: () => void
}

// Create typed store
const useCounterStore = create<CounterStore>()((set) => ({
  count: 0,
  increment: () => set((state) => ({ count: state.count + 1 })),
  decrement: () => set((state) => ({ count: state.count - 1 })),
}))

Key Points:

• Separate interface for state + actions
• Use create<T>()() syntax (currying for middleware)
• Full IDE autocomplete and type checking

Pattern 3: Persistent Store

For state that survives page reloads:

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

interface UserPreferences {
  theme: 'light' | 'dark' | 'system'
  language: string
  setTheme: (theme: UserPreferences['theme']) => void
  setLanguage: (language: string) => void
}

const usePreferencesStore = create<UserPreferences>()(
  persist(
    (set) => ({
      theme: 'system',
      language: 'en',
      setTheme: (theme) => set({ theme }),
      setLanguage: (language) => set({ language }),
    }),
    {
      name: 'user-preferences', // unique name in localStorage
      storage: createJSONStorage(() => localStorage), // optional: defaults to localStorage
    },
  ),
)

Why this matters:

• State automatically saved to localStorage
• Restored on page reload
• Works with sessionStorage too
• Handles serialization automatically

---

Critical Rules

Always Do

✅ Use create<T>()() (double parentheses) in TypeScript for middleware compatibility ✅ Define separate interfaces for state and actions ✅ Use selector functions to extract specific state slices ✅ Use set with updater functions for derived state: set((state) => ({ count: state.count + 1 })) ✅ Use unique names for persist middleware storage keys ✅ Handle Next.js hydration with hasHydrated flag pattern ✅ Use shallow for selecting multiple values ✅ Keep actions pure (no side effects except state updates)

Never Do

❌ Use create<T>(...) (single parentheses) in TypeScript - breaks middleware types ❌ Mutate state directly: set((state) => { state.count++; return state }) - use immutable updates ❌ Create new objects in selectors: useStore((state) => ({ a: state.a })) - causes infinite renders ❌ Use same storage name for multiple stores - causes data collisions ❌ Access localStorage during SSR without hydration check ❌ Use Zustand for server state - use TanStack Query instead ❌ Export store instance directly - always export the hook

---

Known Issues Prevention

This skill prevents 5 documented issues:

Issue #1: Next.js Hydration Mismatch

Error: "Text content does not match server-rendered HTML" or "Hydration failed"

Source:

• DEV Community: Persist middleware in Next.js
• GitHub Discussions #2839

Why It Happens: Persist middleware reads from localStorage on client but not on server, causing state mismatch.

Prevention:

import { create } from 'zustand'
import { persist } from 'zustand/​middleware'

interface StoreWithHydration {
  count: number
  _hasHydrated: boolean
  setHasHydrated: (hydrated: boolean) => void
  increase: () => void
}

const useStore = create<StoreWithHydration>()(
  persist(
    (set) => ({
      count: 0,
      _hasHydrated: false,
      setHasHydrated: (hydrated) => set({ _hasHydrated: hydrated }),
      increase: () => set((state) => ({ count: state.count + 1 })),
    }),
    {
      name: 'my-store',
      onRehydrateStorage: () => (state) => {
        state?.setHasHydrated(true)
      },
    },
  ),
)

// In component
function MyComponent() {
  const hasHydrated = useStore((state) => state._hasHydrated)

  if (!hasHydrated) {
    return <div>Loading...</​div>
  }

  // Now safe to render with persisted state
  return <ActualContent />
}

Issue #2: TypeScript Double Parentheses Missing

Error: Type inference fails, StateCreator types break with middleware

Source: Official Zustand TypeScript Guide

Why It Happens: The currying syntax create<T>()() is required for middleware to work with TypeScript inference.

Prevention:

// ❌ WRONG - Single parentheses
const useStore = create<MyStore>((set) => ({
  // ...
}))

// ✅ CORRECT - Double parentheses
const useStore = create<MyStore>()((set) => ({
  // ...
}))

Rule: Always use create<T>()() in TypeScript, even without middleware (future-proof).

Issue #3: Persist Middleware Import Error

Error: "Attempted import error: 'createJSONStorage' is not exported from 'zustand/​middleware'"

Source: GitHub Discussion #2839

Why It Happens: Wrong import path or version mismatch between zustand and build tools.

Prevention:

// ✅ CORRECT imports for v5
import { create } from 'zustand'
import { persist, createJSONStorage } from 'zustand/​middleware'

// Verify versions
// [email protected] includes createJSONStorage
// [email protected] uses different API

// Check your package.json
// "zustand": "^5.0.8"

Issue #4: Infinite Render Loop

Error: Component re-renders infinitely, browser freezes

Source: GitHub Discussions #2642

Why It Happens: Creating new object references in selectors causes Zustand to think state changed.

Prevention:

import { shallow } from 'zustand/​shallow'

// ❌ WRONG - Creates new object every time
const { bears, fishes } = useStore((state) => ({
  bears: state.bears,
  fishes: state.fishes,
}))

// ✅ CORRECT Option 1 - Select primitives separately
const bears = useStore((state) => state.bears)
const fishes = useStore((state) => state.fishes)

// ✅ CORRECT Option 2 - Use shallow for multiple values
const { bears, fishes } = useStore(
  (state) => ({ bears: state.bears, fishes: state.fishes }),
  shallow,
)

Issue #5: Slices Pattern TypeScript Complexity

Error: StateCreator types fail to infer, complex middleware types break

Source: Official Slices Pattern Guide

Why It Happens: Combining multiple slices requires explicit type annotations for middleware compatibility.

Prevention:

import { create, StateCreator } from 'zustand'

// Define slice types
interface BearSlice {
  bears: number
  addBear: () => void
}

interface FishSlice {
  fishes: number
  addFish: () => void
}

// Create slices with proper types
const createBearSlice: StateCreator<
  BearSlice & FishSlice,  // Combined store type
  [],                      // Middleware mutators (empty if none)
  [],                      // Chained middleware (empty if none)
  BearSlice               // This slice's type
> = (set) => ({
  bears: 0,
  addBear: () => set((state) => ({ bears: state.bears + 1 })),
})

const createFishSlice: StateCreator<
  BearSlice & FishSlice,
  [],
  [],
  FishSlice
> = (set) => ({
  fishes: 0,
  addFish: () => set((state) => ({ fishes: state.fishes + 1 })),
})

// Combine slices
const useStore = create<BearSlice & FishSlice>()((...a) => ({
  ...createBearSlice(...a),
  ...createFishSlice(...a),
}))

---

Middleware Configuration

Persist Middleware (localStorage)

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

interface MyStore {
  data: string[]
  addItem: (item: string) => void
}

const useStore = create<MyStore>()(
  persist(
    (set) => ({
      data: [],
      addItem: (item) => set((state) => ({ data: [...state.data, item] })),
    }),
    {
      name: 'my-storage',
      storage: createJSONStorage(() => localStorage),
      partialize: (state) => ({ data: state.data }), // Only persist 'data'
    },
  ),
)

Devtools Middleware (Redux DevTools)

import { create } from 'zustand'
import { devtools } from 'zustand/​middleware'

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

const useStore = create<CounterStore>()(
  devtools(
    (set) => ({
      count: 0,
      increment: () =>
        set(
          (state) => ({ count: state.count + 1 }),
          undefined,
          'counter/​increment', // Action name in DevTools
        ),
    }),
    { name: 'CounterStore' }, // Store name in DevTools
  ),
)

Combining Multiple Middlewares

import { create } from 'zustand'
import { devtools, persist } from 'zustand/​middleware'

const useStore = create<MyStore>()(
  devtools(
    persist(
      (set) => ({
        // store definition
      }),
      { name: 'my-storage' },
    ),
    { name: 'MyStore' },
  ),
)

Order matters: devtools(persist(...)) shows persist actions in DevTools.

---

Common Patterns

Pattern: Computed/​Derived Values

interface StoreWithComputed {
  items: string[]
  addItem: (item: string) => void
  // Computed in selector, not stored
}

const useStore = create<StoreWithComputed>()((set) => ({
  items: [],
  addItem: (item) => set((state) => ({ items: [...state.items, item] })),
}))

// Use in component
function ItemCount() {
  const count = useStore((state) => state.items.length)
  return <div>{count} items</​div>
}

Pattern: Async Actions

interface AsyncStore {
  data: string | null
  isLoading: boolean
  error: string | null
  fetchData: () => Promise<void>
}

const useAsyncStore = create<AsyncStore>()((set) => ({
  data: null,
  isLoading: false,
  error: null,
  fetchData: async () => {
    set({ isLoading: true, error: null })
    try {
      const response = await fetch('/​api/​data')
      const data = await response.text()
      set({ data, isLoading: false })
    } catch (error) {
      set({ error: (error as Error).message, isLoading: false })
    }
  },
}))

Pattern: Resetting Store

interface ResettableStore {
  count: number
  name: string
  increment: () => void
  reset: () => void
}

const initialState = {
  count: 0,
  name: '',
}

const useStore = create<ResettableStore>()((set) => ({
  ...initialState,
  increment: () => set((state) => ({ count: state.count + 1 })),
  reset: () => set(initialState),
}))

Pattern: Selector with Params

interface TodoStore {
  todos: Array<{ id: string; text: string; done: boolean }>
  addTodo: (text: string) => void
  toggleTodo: (id: string) => void
}

const useStore = create<TodoStore>()((set) => ({
  todos: [],
  addTodo: (text) =>
    set((state) => ({
      todos: [...state.todos, { id: Date.now().toString(), text, done: false }],
    })),
  toggleTodo: (id) =>
    set((state) => ({
      todos: state.todos.map((todo) =>
        todo.id === id ? { ...todo, done: !todo.done } : todo
      ),
    })),
}))

// Use with parameter
function Todo({ id }: { id: string }) {
  const todo = useStore((state) => state.todos.find((t) => t.id === id))
  const toggleTodo = useStore((state) => state.toggleTodo)

  if (!todo) return null

  return (
    <div>
      <input
        type="checkbox"
        checked={todo.done}
        onChange={() => toggleTodo(id)}
      />
      {todo.text}
    </​div>
  )
}

---

Using Bundled Resources

Templates (templates/)

This skill includes 8 ready-to-use template files:

• basic-store.ts - Minimal JavaScript store example
• typescript-store.ts - Properly typed TypeScript store
• persist-store.ts - localStorage persistence with migration
• slices-pattern.ts - Modular store organization
• devtools-store.ts - Redux DevTools integration
• nextjs-store.ts - SSR-safe Next.js store with hydration
• computed-store.ts - Derived state patterns
• async-actions-store.ts - Async operations with loading states

Example Usage:

# Copy template to your project
cp ~/​.claude/​skills/​zustand-state-management/​templates/​typescript-store.ts src/​store/

When to use each:

• Use basic-store.ts for quick prototypes
• Use typescript-store.ts for most production apps
• Use persist-store.ts when state needs to survive page reloads
• Use slices-pattern.ts for large, complex stores (100+ lines)
• Use nextjs-store.ts for Next.js projects with SSR

References (references/)

Deep-dive documentation for complex scenarios:

• middleware-guide.md - Complete middleware documentation (persist, devtools, immer, custom)
• typescript-patterns.md - Advanced TypeScript patterns and troubleshooting
• nextjs-hydration.md - SSR, hydration, and Next.js best practices
• migration-guide.md - Migrating from Redux, Context API, or Zustand v4

When Claude should load these:

• Load middleware-guide.md when user asks about persistence, devtools, or custom middleware
• Load typescript-patterns.md when encountering complex type inference issues
• Load nextjs-hydration.md for Next.js-specific problems
• Load migration-guide.md when migrating from other state management solutions

Scripts (scripts/)

• check-versions.sh - Verify Zustand version and compatibility

Usage:

cd your-project/
~/​.claude/​skills/​zustand-state-management/​scripts/​check-versions.sh

---

Advanced Topics

Vanilla Store (Without React)

import { createStore } from 'zustand/​vanilla'

const store = createStore<CounterStore>()((set) => ({
  count: 0,
  increment: () => set((state) => ({ count: state.count + 1 })),
}))

// Subscribe to changes
const unsubscribe = store.subscribe((state) => {
  console.log('Count changed:', state.count)
})

// Get current state
console.log(store.getState().count)

// Update state
store.getState().increment()

// Cleanup
unsubscribe()

Custom Middleware

import { StateCreator, StoreMutatorIdentifier } from 'zustand'

type Logger = <T>(
  f: StateCreator<T, [], []>,
  name?: string,
) => StateCreator<T, [], []>

const logger: Logger = (f, name) => (set, get, store) => {
  const loggedSet: typeof set = (...a) => {
    set(...(a as Parameters<typeof set>))
    console.log(`[${name}]:`, get())
  }
  return f(loggedSet, get, store)
}

// Use custom middleware
const useStore = create<MyStore>()(
  logger((set) => ({
    // store definition
  }), 'MyStore'),
)

Immer Middleware (Mutable Updates)

import { create } from 'zustand'
import { immer } from 'zustand/​middleware/​immer'

interface TodoStore {
  todos: Array<{ id: string; text: string }>
  addTodo: (text: string) => void
}

const useStore = create<TodoStore>()(
  immer((set) => ({
    todos: [],
    addTodo: (text) =>
      set((state) => {
        // Mutate directly with Immer
        state.todos.push({ id: Date.now().toString(), text })
      }),
  })),
)

---

Dependencies

Required:

• [email protected] - State management library
• [email protected]+ - React framework

Optional:

• @types/​node - For TypeScript path resolution
• immer - For mutable update syntax
• Redux DevTools Extension - For devtools middleware

---

Official Documentation

• Zustand: https://zustand.docs.pmnd.rs/
• GitHub: https://github.com/pmndrs/zustand
• TypeScript Guide: https://zustand.docs.pmnd.rs/guides/typescript
• Slices Pattern: https://github.com/pmndrs/zustand/blob/main/docs/guides/slices-pattern.md
• Context7 Library ID: /​pmndrs/​zustand

---

Package Versions (Verified 2025-10-24)

{
  "dependencies": {
    "zustand": "^5.0.8",
    "react": "^19.0.0"
  },
  "devDependencies": {
    "@types/​node": "^22.0.0",
    "typescript": "^5.0.0"
  }
}

Compatibility:

• React 18+, React 19 ✅
• TypeScript 5+ ✅
• Next.js 14+, Next.js 15+ ✅
• Vite 5+ ✅

---

Troubleshooting

Problem: Store updates don't trigger re-renders

Solution: Ensure you're using selector functions, not destructuring: const bears = useStore(state => state.bears) not const { bears } = useStore()

Problem: TypeScript errors with middleware

Solution: Use double parentheses: create<T>()() not create<T>()

Problem: Persist middleware causes hydration error

Solution: Implement _hasHydrated flag pattern (see Issue #1)

Problem: Actions not showing in Redux DevTools

Solution: Pass action name as third parameter to set: set(newState, undefined, 'actionName')

Problem: Store state resets unexpectedly

Solution: Check if using HMR (hot module replacement) - Zustand resets on module reload in development

---

Complete Setup Checklist

Use this checklist to verify your Zustand setup:

• Installed [email protected] or later
• Created store with proper TypeScript types
• Used create<T>()() double parentheses syntax
• Tested selector functions in components
• Verified components only re-render when selected state changes
• If using persist: Configured unique storage name
• If using persist: Implemented hydration check for Next.js
• If using devtools: Named actions for debugging
• If using slices: Properly typed StateCreator for each slice
• All actions are pure functions
• No direct state mutations
• Store works in production build

---

Questions? Issues?

1. Check references/​typescript-patterns.md for TypeScript help
2. Check references/​nextjs-hydration.md for Next.js issues
3. Check references/​middleware-guide.md for persist/​devtools help
4. Official docs: https://zustand.docs.pmnd.rs/
5. GitHub issues: https://github.com/pmndrs/zustand/issues