TypeScript

Vue Query is now written in TypeScript to make sure the library and your projects are type-safe!

Things to keep in mind:

• Types currently require using TypeScript v4.7 or greater
• Changes to types in this repository are considered non-breaking and are usually released as patch semver changes (otherwise every type enhancement would be a major version!).
• It is highly recommended that you lock your vue-query package version to a specific patch release and upgrade with the expectation that types may be fixed or upgraded between any release
• The non-type-related public API of Vue Query still follows semver very strictly.

Types in Vue Query generally flow through very well so that you don't have to provide type annotations for yourself

const { data } = useQuery({
  //    ^? const data: Ref<number> | Ref<undefined>
  queryKey: ['test'],
  queryFn: () => Promise.resolve(5),
})

const { data } = useQuery({
  //    ^? const data: Ref<number> | Ref<undefined>
  queryKey: ['test'],
  queryFn: () => Promise.resolve(5),
})

typescript playground

const { data } = useQuery({
  //      ^? const data: Ref<string> | Ref<undefined>
  queryKey: ['test'],
  queryFn: () => Promise.resolve(5),
  select: (data) => data.toString(),
})

const { data } = useQuery({
  //      ^? const data: Ref<string> | Ref<undefined>
  queryKey: ['test'],
  queryFn: () => Promise.resolve(5),
  select: (data) => data.toString(),
})

typescript playground

This works best if your queryFn has a well-defined returned type. Keep in mind that most data fetching libraries return any per default, so make sure to extract it to a properly typed function:

const fetchGroups = (): Promise<Group[]> =>
  axios.get('/groups').then((response) => response.data)

const { data } = useQuery({ queryKey: ['groups'], queryFn: fetchGroups })
//      ^? const data: Ref<Group[]> | Ref<undefined>

const fetchGroups = (): Promise<Group[]> =>
  axios.get('/groups').then((response) => response.data)

const { data } = useQuery({ queryKey: ['groups'], queryFn: fetchGroups })
//      ^? const data: Ref<Group[]> | Ref<undefined>

typescript playground

Vue Query uses a discriminated union type for the query result, discriminated by the status field and the derived status boolean flags. This will allow you to check for e.g. success status to make data defined:

const { data, isSuccess } = reactive(
  useQuery({
    queryKey: ['test'],
    queryFn: () => Promise.resolve(5),
  }),
)

if (isSuccess) {
  data
  // ^? const data: number
}

const { data, isSuccess } = reactive(
  useQuery({
    queryKey: ['test'],
    queryFn: () => Promise.resolve(5),
  }),
)

if (isSuccess) {
  data
  // ^? const data: number
}

typescript playground

The type for error defaults to Error, because that is what most users expect.

const { error } = useQuery({ queryKey: ['groups'], queryFn: fetchGroups })
//      ^? const error: Ref<unknown>

if (error.value instanceof Error) {
  error.value
  //     ^? const error: Error
}

const { error } = useQuery({ queryKey: ['groups'], queryFn: fetchGroups })
//      ^? const error: Ref<unknown>

if (error.value instanceof Error) {
  error.value
  //     ^? const error: Error
}

typescript playground

If you want to throw a custom error, or something that isn't an Error at all, you can specify the type of the error field:

However, this has the drawback that type inference for all other generics of useQuery will not work anymore. It is generally not considered a good practice to throw something that isn't an Error, so if you have a subclass like AxiosError you can use type narrowing to make the error field more specific:

TanStack Query v5 allows for a way to set a global Error type for everything, without having to specify generics on call-sides, by amending the Register interface. This will make sure inference still works, but the error field will be of the specified type:

If you are using TypeScript, you can use the skipToken to disable a query. This is useful when you want to disable a query based on a condition, but you still want to keep the query to be type safe. Read more about it in the Disabling Queries guide.