> ## 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

> Solid.js primitive 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>
): Accessor<TSelected>
```

A Solid.js primitive that subscribes to a TanStack Store atom and returns a signal accessor. The signal will update 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="Accessor<TSelected>" type="Accessor<TSelected>">
  A Solid.js signal accessor function that returns the selected state value.
</ResponseField>

## Usage

### Basic Usage

```tsx theme={null}
import { useStore } from '@tanstack/solid-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/solid-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} />
    </div>
  )
}
```

### Custom Equality Function

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

// Only update when count changes by more than 10
const customEqual = (a, b) => Math.abs(a - b) < 10

function ApproximateCounter() {
  const count = useStore(
    store,
    (state) => state.count,
    { equal: customEqual }
  )

  return <div>Count (±10): {count()}</div>
}
```

### Using Entire State

```tsx theme={null}
import { useStore } from '@tanstack/solid-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 Derived State

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

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

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

### With Show Component

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

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

  return (
    <Show
      when={isLoggedIn()}
      fallback={<div>Please log in</div>}
    >
      <div>Welcome, {user().name}!</div>
    </Show>
  )
}
```

## Notes

* Returns a Solid.js **signal accessor** - call it as a function to get the value
* Uses `createSignal` internally for fine-grained reactivity
* Automatically cleans up subscriptions using `onCleanup`
* Defaults to `shallow` equality comparison for optimal performance
* The selector is evaluated immediately on creation and on each update
* Integrates seamlessly with Solid's reactive primitives like `createMemo`, `createEffect`, etc.