[Home](./index.md) > [@firebase/firestore](./firestore.md) > [lite](./firestore_lite.md) > [WriteBatch](./firestore_lite.writebatch.md) > [update](./firestore_lite.writebatch.update_1.md) ## WriteBatch.update() method Updates fields in the document referred to by this [DocumentReference](./firestore_.documentreference.md). The update will fail if applied to a document that does not exist. Nested fields can be update by providing dot-separated field path strings or by providing `FieldPath` objects. Signature: ```typescript update(documentRef: DocumentReference, field: string | FieldPath, value: unknown, ...moreFieldsAndValues: unknown[]): WriteBatch; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | documentRef | [DocumentReference](./firestore_lite.documentreference.md)<unknown> | A reference to the document to be updated. | | field | string \| [FieldPath](./firestore_lite.fieldpath.md) | The first field to update. | | value | unknown | The first value. | | moreFieldsAndValues | unknown\[\] | Additional key value pairs. | Returns: [WriteBatch](./firestore_lite.writebatch.md) This `WriteBatch` instance. Used for chaining method calls.