<PageCard>

# autoUpdate

Automatically updates the position of the floating element when
necessary to ensure it stays anchored.

<ShowFor packages={['core']}>
  <Notice type="error" title="Unavailable API">
    This is a DOM API and is therefore not available for
    `@floating-ui/core`. If you are not using that package,
    change your package with the red package switcher at the top
    of the page.
  </Notice>
</ShowFor>

<ShowFor packages={['react-native']}>
  <Notice type="error" title="Unavailable API">
    This is a DOM API and is therefore not available for
    `@floating-ui/react-native`. If you are not using that
    package, change your package with the red package switcher at
    the top of the page.
  </Notice>
</ShowFor>

<ShowFor packages={['dom']}>

```js
import {autoUpdate} from '@floating-ui/dom';
```

</ShowFor>

<ShowFor packages={['react']}>

```js
import {autoUpdate} from '@floating-ui/react';
```

</ShowFor>

<ShowFor packages={['react-dom']}>

```js
import {autoUpdate} from '@floating-ui/react-dom';
```

</ShowFor>

<ShowFor packages={['vue']}>

```js
import {autoUpdate} from '@floating-ui/vue';
```

</ShowFor>

</PageCard>

To ensure the floating element remains anchored to its reference
element, such as when scrolling and resizing the screen, its
position needs to be continually updated when necessary.

To solve this, `autoUpdate(){:js}` adds listeners that will
automatically call an update function which invokes
`computePosition(){:js}` when necessary. Updates typically take
only ~1ms.

## Usage

It's important that this function is only called/set-up when the
floating element is open on the screen, and cleaned up when it's
removed. Otherwise, it can cause severe performance degradation,
especially with many floating elements being created.

<ShowFor packages={['react', 'react-dom']}>

If you're conditionally rendering the floating element
(recommended), use the `whileElementsMounted{:.key}` option:

```js
useFloating({
  whileElementsMounted: autoUpdate,
});
```

`whileElementsMounted{:.key}` automatically handles calling and
cleaning up `autoUpdate` based on the presence of the reference
and floating element.

Alternatively, if you've hidden the floating element with CSS
(based on an `isOpen` state), use an Effect to handle it instead:

```js {18}
const [isOpen, setIsOpen] = useState(false);
const {update, refs, elements} = useFloating();

useEffect(() => {
  if (isOpen && elements.reference && elements.floating) {
    const cleanup = autoUpdate(
      elements.reference,
      elements.floating,
      update,
    );
    return cleanup;
  }
}, [isOpen, elements, update]);

return (
  <div
    ref={refs.setFloating}
    style={{display: isOpen ? 'block' : 'none'}}
  />
);
```

</ShowFor>

<ShowFor packages={['vue']}>

### Conditional rendering

If you're conditionally rendering the floating element with
`v-if{:.keyword}` (recommended), use the
`whileElementsMounted{:.key}` option:

```js
useFloating(reference, floating, {
  whileElementsMounted: autoUpdate,
});
```

`whileElementsMounted{:.key}` automatically handles calling and
cleaning up `autoUpdate` based on the presence of the reference
and floating element.

### CSS

Alternatively, if you've hidden the floating element with CSS
such as `v-show{:.keyword}` using an open state, manually handle
invocation and clean up. The composable returns an update method
and `autoUpdate` a cleanup function:

```js
const {update} = useFloating(reference, floating);
```

You can watch the open state and handle the lifecycle:

```js
const cleanup = autoUpdate(
  reference.value,
  floating.value,
  update,
);
```

</ShowFor>

<ShowFor packages={['dom']}>

Call `autoUpdate(){:js}` **only** when the floating element is
open or mounted:

```js
// This function will get called repeatedly.
function updatePosition() {
  computePosition(referenceEl, floatingEl).then(({x, y}) => {
    // ...
  });
}

// Mount the floating element to the DOM, such as on hover
// or click.
document.body.append(floatingEl);
// Start auto updates.
const cleanup = autoUpdate(
  referenceEl,
  floatingEl,
  updatePosition,
);
```

Then, when the user unhovers or clicks away, unmount the floating
element and ensure you call the **cleanup** function to stop the
auto updates:

```js
// Remove the floating element from the DOM, such as on blur
// or outside click.
floatingEl.remove();
// Stop auto updates.
cleanup();
```

</ShowFor>

## Options

These are the options you can pass as a fourth argument to
`autoUpdate(){:js}`.

```ts
interface AutoUpdateOptions {
  ancestorScroll?: boolean;
  ancestorResize?: boolean;
  elementResize?: boolean;
  layoutShift?: boolean;
  animationFrame?: boolean;
}
```

### `ancestorScroll{:.key}`

default: `true{:js}`

Whether to update the position when an overflow ancestor is
scrolled.

<ShowFor packages={['dom']}>

```js
const cleanup = autoUpdate(referenceEl, floatingEl, update, {
  ancestorScroll: false,
});
```

</ShowFor>

<ShowFor packages={['react', 'react-dom']}>

```js
useFloating({
  whileElementsMounted(referenceEl, floatingEl, update) {
    const cleanup = autoUpdate(referenceEl, floatingEl, update, {
      ancestorScroll: false,
    });
    return cleanup;
  },
});
```

</ShowFor>

<ShowFor packages={['vue']}>

```js
useFloating(reference, floating, {
  whileElementsMounted(referenceEl, floatingEl, update) {
    const cleanup = autoUpdate(referenceEl, floatingEl, update, {
      ancestorScroll: false,
    });
    return cleanup;
  },
});
```

</ShowFor>

### `ancestorResize{:.key}`

default: `true{:js}`

Whether to update the position when an overflow ancestor is
resized. This uses the `resize{:.string}` event.

<ShowFor packages={['dom']}>

```js
const cleanup = autoUpdate(referenceEl, floatingEl, update, {
  ancestorResize: false,
});
```

</ShowFor>

<ShowFor packages={['react', 'react-dom']}>

```js
useFloating({
  whileElementsMounted(referenceEl, floatingEl, update) {
    const cleanup = autoUpdate(referenceEl, floatingEl, update, {
      ancestorResize: false,
    });
    return cleanup;
  },
});
```

</ShowFor>

<ShowFor packages={['vue']}>

```js
useFloating(reference, floating, {
  whileElementsMounted(referenceEl, floatingEl, update) {
    const cleanup = autoUpdate(referenceEl, floatingEl, update, {
      ancestorResize: false,
    });
    return cleanup;
  },
});
```

</ShowFor>

### `elementResize{:.key}`

default: `true{:js}`

Whether to update the position when either the reference or
floating elements resized. This uses a `ResizeObserver{:.class}`.

<ShowFor packages={['dom']}>

```js
const cleanup = autoUpdate(referenceEl, floatingEl, update, {
  elementResize: false,
});
```

</ShowFor>

<ShowFor packages={['react', 'react-dom']}>

```js
useFloating({
  whileElementsMounted(referenceEl, floatingEl, update) {
    const cleanup = autoUpdate(referenceEl, floatingEl, update, {
      elementResize: false,
    });
    return cleanup;
  },
});
```

</ShowFor>

<ShowFor packages={['vue']}>

```js
useFloating(reference, floating, {
  whileElementsMounted(referenceEl, floatingEl, update) {
    const cleanup = autoUpdate(referenceEl, floatingEl, update, {
      elementResize: false,
    });
    return cleanup;
  },
});
```

</ShowFor>

<Notice type="warning" title="Browser support">
  To support old browsers, polyfill `ResizeObserver{:.class}`, or update manually when the elements resize.
</Notice>

### `layoutShift{:.key}`

default: `true{:js}`

Whether to update the position of the floating element if the
reference element moved on the screen as the result of layout
shift.

<ShowFor packages={['dom']}>

```js
const cleanup = autoUpdate(referenceEl, floatingEl, update, {
  layoutShift: false,
});
```

</ShowFor>

<ShowFor packages={['react', 'react-dom']}>

```js
useFloating({
  whileElementsMounted(referenceEl, floatingEl, update) {
    const cleanup = autoUpdate(referenceEl, floatingEl, update, {
      layoutShift: false,
    });
    return cleanup;
  },
});
```

</ShowFor>

<ShowFor packages={['vue']}>

```js
useFloating(reference, floating, {
  whileElementsMounted(referenceEl, floatingEl, update) {
    const cleanup = autoUpdate(referenceEl, floatingEl, update, {
      layoutShift: false,
    });
    return cleanup;
  },
});
```

</ShowFor>

<Notice type="warning" title="Browser support">
  To support old browsers, polyfill `IntersectionObserver{:.class}`, or update manually when the reference element moves.
</Notice>

### `animationFrame{:.key}`

default: `false{:js}`

Whether to update the position of the floating element on every
animation frame if required. While optimized for performance, it
should be used sparingly in the following cases:

- The reference element is animating on the screen with
  `transform`s.
- Ensure a nested floating element is anchored when it's outside
  of ancestor floating elements' scrolling contexts.

<ShowFor packages={['dom']}>

```js
const cleanup = autoUpdate(referenceEl, floatingEl, update, {
  animationFrame: true,
});
```

</ShowFor>

<ShowFor packages={['react', 'react-dom']}>

```js
useFloating({
  whileElementsMounted(referenceEl, floatingEl, update) {
    const cleanup = autoUpdate(referenceEl, floatingEl, update, {
      animationFrame: true,
    });
    return cleanup;
  },
});
```

</ShowFor>

<ShowFor packages={['vue']}>

```js
useFloating(reference, floating, {
  whileElementsMounted(referenceEl, floatingEl, update) {
    const cleanup = autoUpdate(referenceEl, floatingEl, update, {
      animationFrame: true,
    });
    return cleanup;
  },
});
```

</ShowFor>
