--- NOTE: do not edit this file, it is generated in apps/svelte.dev/scripts/sync-docs/index.ts title: svelte/attachments --- ```js // @noErrors import { createAttachmentKey, fromAction } from 'svelte/attachments'; ``` ## createAttachmentKey

Available since 5.29

Creates an object key that will be recognised as an attachment when the object is spread onto an element, as a programmatic alternative to using `{@attach ...}`. This can be useful for library authors, though is generally not needed when building an app. ```svelte ```

```dts function createAttachmentKey(): symbol; ```

## fromAction Converts an [action](/docs/svelte/use) into an [attachment](/docs/svelte/@attach) keeping the same behavior. It's useful if you want to start using attachments on components but you have actions provided by a library. Note that the second argument, if provided, must be a function that _returns_ the argument to the action function, not the argument itself. ```svelte

...

bar)}>...

```

```dts function fromAction< E extends EventTarget, T extends unknown >( action: | Action | ((element: E, arg: T) => void | ActionReturn), fn: () => T ): Attachment; ```

```dts function fromAction( action: | Action | ((element: E) => void | ActionReturn) ): Attachment; ```

## Attachment An [attachment](/docs/svelte/@attach) is a function that runs when an element is mounted to the DOM, and optionally returns a function that is called when the element is later removed. It can be attached to an element with an `{@attach ...}` tag, or by spreading an object containing a property created with [`createAttachmentKey`](/docs/svelte/svelte-attachments#createAttachmentKey).

```dts interface Attachment {/*…*/} ```

```dts (element: T): void | (() => void); ```