> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/TanStack/store/llms.txt
> Use this file to discover all available pages before exploring further.

# useStore

> Preact hook for subscribing to TanStack Store state

## Reference

### `useStore`

```tsx theme={null}
function useStore<TState, TSelected = NoInfer<TState>>(
  store: Atom<TState> | ReadonlyAtom<TState>,
  selector?: (state: NoInfer<TState>) => TSelected,
  options?: UseStoreOptions<TSelected>
): TSelected
```

A Preact hook that subscribes to a TanStack Store atom and returns the selected state. The component will re-render when the selected state changes according to the equality function.

<ParamField path="store" type="Atom<TState> | ReadonlyAtom<TState>">
  The store atom to subscribe to.
</ParamField>

<ParamField path="selector" type="(state: TState) => TSelected" default="(d) => d">
  Optional function that selects a slice of state from the atom. Defaults to returning the entire state.
</ParamField>

<ParamField path="options" type="UseStoreOptions<TSelected>">
  Optional configuration object.

  <Expandable title="properties">
    <ResponseField name="equal" type="(a: TSelected, b: TSelected) => boolean" default="shallow">
      Equality function to determine if the selected state has changed. Defaults to `shallow` comparison.
    </ResponseField>
  </Expandable>
</ParamField>

### Returns

<ResponseField name="TSelected" type="TSelected">
  The selected state value from the atom.
</ResponseField>

## Usage

### Basic Usage

```tsx theme={null}
import { useStore } from '@tanstack/preact-store'
import { store } from './store'

function Counter() {
  const count = useStore(store, (state) => state.count)

  return <div>Count: {count}</div>
}
```

### Selecting Multiple Values

```tsx theme={null}
import { useStore } from '@tanstack/preact-store'
import { store } from './store'

function UserProfile() {
  const user = useStore(store, (state) => ({
    name: state.user.name,
    email: state.user.email,
    avatar: state.user.avatar
  }))

  return (
    <div>
      <h2>{user.name}</h2>
      <p>{user.email}</p>
      <img src={user.avatar} alt="Avatar" />
    </div>
  )
}
```

### Custom Equality Function

```tsx theme={null}
import { useStore } from '@tanstack/preact-store'
import { store } from './store'

// Use strict reference equality
function TodoList() {
  const todos = useStore(
    store,
    (state) => state.todos,
    { equal: (a, b) => a === b }
  )

  return (
    <ul>
      {todos.map(todo => (
        <li key={todo.id}>{todo.text}</li>
      ))}
    </ul>
  )
}
```

### Using Entire State

```tsx theme={null}
import { useStore } from '@tanstack/preact-store'
import { store } from './store'

function AppState() {
  const state = useStore(store)

  return (
    <div>
      <p>Count: {state.count}</p>
      <p>Name: {state.name}</p>
      <p>Active: {state.isActive ? 'Yes' : 'No'}</p>
    </div>
  )
}
```

### With Shallow Comparison

```tsx theme={null}
import { useStore, shallow } from '@tanstack/preact-store'
import { store } from './store'

function Settings() {
  // Shallow compare the selected object
  const settings = useStore(
    store,
    (state) => ({
      theme: state.settings.theme,
      language: state.settings.language
    }),
    { equal: shallow }
  )

  return (
    <div>
      <p>Theme: {settings.theme}</p>
      <p>Language: {settings.language}</p>
    </div>
  )
}
```

### Selecting Derived Values

```tsx theme={null}
import { useStore } from '@tanstack/preact-store'
import { store } from './store'

function TodoStats() {
  const stats = useStore(store, (state) => {
    const todos = state.todos
    return {
      total: todos.length,
      completed: todos.filter(t => t.done).length,
      pending: todos.filter(t => !t.done).length
    }
  })

  return (
    <div>
      <p>Total: {stats.total}</p>
      <p>Completed: {stats.completed}</p>
      <p>Pending: {stats.pending}</p>
    </div>
  )
}
```

### Conditional Rendering

```tsx theme={null}
import { useStore } from '@tanstack/preact-store'
import { store } from './store'

function AuthView() {
  const isLoggedIn = useStore(store, (state) => state.isLoggedIn)
  const user = useStore(store, (state) => state.user)

  if (!isLoggedIn) {
    return <div>Please log in</div>
  }

  return <div>Welcome, {user.name}!</div>
}
```

### Multiple Store Subscriptions

```tsx theme={null}
import { useStore } from '@tanstack/preact-store'
import { userStore, settingsStore } from './stores'

function Dashboard() {
  const userName = useStore(userStore, (state) => state.name)
  const theme = useStore(settingsStore, (state) => state.theme)

  return (
    <div className={`theme-${theme}`}>
      <h1>Welcome, {userName}</h1>
    </div>
  )
}
```

## Notes

* Implements a custom `useSyncExternalStore` shim for Preact compatibility
* Automatically handles subscription cleanup when the component unmounts
* Defaults to `shallow` equality comparison for optimal performance
* The selector function runs on each potential update - keep it simple or memoize expensive computations
* Built specifically for Preact - does not require `preact/compat`
* Uses `useLayoutEffect` and `useState` internally for synchronization
* Works with both Preact function components and class components (via function children)