---
title: TypeScript | Realtime Database
description: TypeScript usage with React Query Firebase.
---

# TypeScript

The library comes with support for a full typesafe API.

## Typing data values

The `useDatabaseSnapshot` returns a [`DataSnapshot`](https://firebase.google.com/docs/reference/js/database.datasnapshot.md#datasnapshotforeach)
returns an instance whose `val()` method retuns the data as `any`. In this case, you'll need to cast it.

However, the `useDatabaseValue` hook instead returns the raw data of the reference node, allowing us to
provide the data type to the hook:

```ts
type Product = {
  name: string;
  price: number;
};

const product = useDatabaseValue<Product>(["products", id], database, dbRef);

if (product.isSuccess) {
  // product.data is now typed!
  console.log(product.data.name);
  console.log(product.data.price);
}
```

## Typing mutations

The mutation hooks allow us to provide a type which ensures the mutation calls are type safe.

When setting data:

```ts
const mutation = useDatabaseSetMutation<number>(dbRef);
mutation.mutate(1337);
```

When updating data, the type must extend the expected update values (`Record<string, unknown>`):

```ts
type Updates = {
  age: number;
  "address/line1": string;
};

const mutation = useDatabaseUpdateMutation<Updates>(dbRef);

mutation.mutate({
  age: 18,
  "address/line1": "Mountain View",
});
```

When working with Transactions, you can type the expected value provided to the transaction function:

```ts
type Post = {
  title: string;
  likes: number;
};

const mutation = useDatabaseTransaction<Post>(dbRef, (post: Post | null) => {
  // ...
});

mutation.mutate();
```