# DowncastAttributeCreatorFunction

typedef

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/conversion/downcasthelpers.ts#L3096)

#### Parameters

* `attributeValue: unknown`

  The model attribute value to be converted to the view attribute element.

* `conversionApi: DowncastConversionApi`

  The conversion interface.

* `data: object`

  Additional information about the change (same as for [`attribute`](module_engine_conversion_downcastdispatcher-DowncastDispatcher.md#event-attribute) event).

  Properties

  * `data.attributeKey: string`

    Attribute key.

  * `data.attributeNewValue: unknown`

    New attribute value.

  * `data.attributeOldValue: unknown`

    Attribute value before the change. This is `null` when selection attribute is converted.

  * `data.item: ModelItem`

    Changed item or converted selection.

  * `data.range: ModelRange`

    Range spanning over changed item or selection range.

#### Returns

* `DowncastAttributeDescriptor | null`

  A `{ key, value }` object. If `key` is `'class'`, `value` can be a `String` or an array of `String`s. If `key` is `'style'`, `value` is an object with key-value pairs. In other cases, `value` is a `String`.

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Full index of the CKEditor 5 API reference: [llms.txt](llms.txt)