npm install zustand

import { create } from 'zustand'

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

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

const bears = useBearStore((state) => state.bears)  // Only re-renders when bears changes
const increase = useBearStore((state) => state.increase)

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

interface CounterStore { count: number; increment: () => void }
const useStore = create<CounterStore>()((set) => ({
  count: 0,
  increment: () => set((state) => ({ count: state.count + 1 })),
}))

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

const useStore = create<UserPreferences>()(
  persist(
    (set) => ({ theme: 'system', setTheme: (theme) => set({ theme }) }),
    { name: 'user-preferences', storage: createJSONStorage(() => localStorage) },
  ),
)

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 />
}

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

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

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

// Verify versions
// zustand@5.0.9 includes createJSONStorage
// zustand@4.x uses different API

// Check your package.json
// "zustand": "^5.0.9"

Uncaught Error: Maximum update depth exceeded. This can happen when a component repeatedly calls setState inside componentWillUpdate or componentDidUpdate.

import { useShallow } 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 useShallow hook for multiple values
const { bears, fishes } = useStore(
  useShallow((state) => ({ bears: state.bears, fishes: state.fishes }))
)

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),
}))

npm install zustand@latest  # Ensure v5.0.10+

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

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

import { devtools } from 'zustand/middleware'

const useStore = create<CounterStore>()(
  devtools(
    (set) => ({ count: 0, increment: () => set((s) => ({ count: s.count + 1 }), undefined, 'increment') }),
    { name: 'CounterStore' },
  ),
)

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

const count = useStore((state) => state.items.length)  // Computed on read

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

const initialState = { count: 0, name: '' }
const useStore = create<ResettableStore>()((set) => ({
  ...initialState,
  reset: () => set(initialState),
}))

const todo = useStore((state) => state.todos.find((t) => t.id === id))

import { createStore } from 'zustand/vanilla'

const store = createStore<CounterStore>()((set) => ({ count: 0, increment: () => set((s) => ({ count: s.count + 1 })) }))
const unsubscribe = store.subscribe((state) => console.log(state.count))
store.getState().increment()

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

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

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

import { unstable_ssrSafe } from 'zustand/middleware'

const useStore = create<Store>()(
  unstable_ssrSafe(
    persist(
      (set) => ({ /* state */ }),
      { name: 'my-store' }
    )
  )
)