[Home](./index.md) > [@firebase/firestore](./firestore.md) > [/](./firestore_.md) > [updateDoc](./firestore_.updatedoc_1.md) ## updateDoc() function Updates fields in the document referred to by the specified `DocumentReference` The update will fail if applied to a document that does not exist. Nested fields can be updated by providing dot-separated field path strings or by providing `FieldPath` objects. Signature: ```typescript export declare function updateDoc(reference: DocumentReference, field: string | FieldPath, value: unknown, ...moreFieldsAndValues: unknown[]): Promise; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | reference | [DocumentReference](./firestore_.documentreference.md)<unknown> | A reference to the document to update. | | field | string \| [FieldPath](./firestore_.fieldpath.md) | The first field to update. | | value | unknown | The first value. | | moreFieldsAndValues | unknown\[\] | Additional key value pairs. | Returns: Promise<void> A Promise resolved once the data has been successfully written to the backend (note that it won't resolve while you're offline).