zustand-state-management

Zustand State Management

Status: Production Ready ✅ Last Updated: 2025-11-21 Latest Version: [email protected] Dependencies: React 18+, TypeScript 5+

---

Quick Start (3 Minutes)

1. Install Zustand

bun add zustand  # preferred
# or: npm install 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 (5 Issues)

Issue	Error	Quick Fix
#1 Hydration mismatch	"Text content does not match"	Use _hasHydrated flag + onRehydrateStorage
#2 TypeScript inference	Types break with middleware	Use create<T>()() double parentheses
#3 Import error	"createJSONStorage not exported"	Upgrade to [email protected]+
#4 Infinite loop	Browser freezes	Use shallow or separate selectors
#5 Slices types	StateCreator types fail	Explicit StateCreator<Combined, [], [], Slice>

Most Critical - TypeScript double parentheses:

// ❌ WRONG: create<T>((set) => ...)
// ✅ CORRECT: create<T>()((set) => ...)

See: references/known-issues.md for complete solutions with code examples.

---

Middleware Configuration

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

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

Middleware	Purpose	Import
persist	localStorage/sessionStorage	zustand/middleware
devtools	Redux DevTools integration	zustand/middleware
immer	Mutable update syntax	zustand/middleware/immer

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

See: references/middleware-guide.md for complete middleware documentation.

---

Common Patterns

Pattern	Use Case	Key Technique
Computed values	Derived data	Compute in selector: state.items.length
Async actions	API calls	set({ isLoading: true }) + try/catch
Reset store	Logout, form clear	set(initialState)
Selector with params	Dynamic access	state.todos.find(t => t.id === id)
Multiple stores	Separation of concerns	Create separate create() calls

See: references/common-patterns.md for complete implementations.

---

Advanced Topics

Topic	Use Case	Key API
Vanilla store	Non-React, testing	createStore() from zustand/vanilla
Custom middleware	Logging, timestamps	Wrap StateCreator
Immer	Mutable update syntax	immer() middleware
Subscriptions	Side effects	store.subscribe()

See: references/advanced-topics.md for complete implementations.

---

Bundled Resources

Type	Files
Templates	basic-store.ts, typescript-store.ts, persist-store.ts, slices-pattern.ts, devtools-store.ts, nextjs-store.ts, computed-store.ts, async-actions-store.ts
References	middleware-guide.md, typescript-patterns.md, nextjs-hydration.md, migration-guide.md, known-issues.md, common-patterns.md, advanced-topics.md

---

When to Load References

Reference	Load When...
known-issues.md	Debugging hydration, TypeScript, infinite loop, or slices errors
common-patterns.md	Implementing computed values, async actions, reset patterns
advanced-topics.md	Vanilla stores, custom middleware, Immer, subscriptions
middleware-guide.md	Configuring persist, devtools, or combining middlewares
typescript-patterns.md	Complex type inference issues, StateCreator problems
nextjs-hydration.md	Next.js SSR/hydration problems
migration-guide.md	Migrating from Redux, Context API, or Zustand v4

---

Quick Troubleshooting

Problem	Solution
Store updates don't trigger re-renders	Use selector: useStore(state => state.value) not destructuring
TypeScript errors with middleware	Use create<T>()() double parentheses
Hydration error with persist	Implement _hasHydrated flag pattern
Actions not showing in DevTools	Pass action name: set(newState, undefined, 'actionName')
Store resets unexpectedly	HMR causes reset in development

---

Dependencies

{ "dependencies": { "zustand": "^5.0.8", "react": "^18.0.0+" } }

Compatibility: React 18+, React 19, TypeScript 5+, Next.js 14+, Vite 5+

---

Official Docs: https://zustand.docs.pmnd.rs/ | GitHub: https://github.com/pmndrs/zustand