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## doc() function

Gets a `DocumentReference` instance that refers to a document within `reference` at the specified relative path. If no path is specified, an automatically-generated unique ID will be used for the returned `DocumentReference`<!-- -->.

<b>Signature:</b>

```typescript
export declare function doc<T>(reference: CollectionReference<T>, path?: string, ...pathSegments: string[]): DocumentReference<T>;
```

## Parameters

|  Parameter | Type | Description |
|  --- | --- | --- |
|  reference | [CollectionReference](./firestore_.collectionreference.md)<!-- -->&lt;T&gt; | A reference to a collection. |
|  path | string | A slash-separated path to a document. Has to be omitted to use auto-genrated IDs. |
|  pathSegments | string\[\] | Additional path segments that will be applied relative to the first argument. |

<b>Returns:</b>

[DocumentReference](./firestore_.documentreference.md)<!-- -->&lt;T&gt;

The `DocumentReference` instance.

## Exceptions

If the final path has an odd number of segments and does not point to a document.