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81 lines
3.0 KiB
Markdown
81 lines
3.0 KiB
Markdown
# `useAsyncData`
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Within your pages, components, and plugins you can use useAsyncData to get access to data that resolves asynchronously.
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## Type
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```ts [Signature]
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function useAsyncData(
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handler: (nuxtApp?: NuxtApp) => Promise<DataT>,
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options?: AsyncDataOptions<DataT>
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): AsyncData<DataT>
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function useAsyncData(
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key: string,
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handler: (nuxtApp?: NuxtApp) => Promise<DataT>,
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options?: AsyncDataOptions<DataT>
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): Promise<AsyncData<DataT>>
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type AsyncDataOptions<DataT> = {
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server?: boolean
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lazy?: boolean
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default?: () => DataT | Ref<DataT> | null
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transform?: (input: DataT) => DataT
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pick?: string[]
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watch?: WatchSource[]
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initialCache?: boolean
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}
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interface RefreshOptions {
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_initial?: boolean
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}
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type AsyncData<DataT, ErrorT> = {
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data: Ref<DataT | null>
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pending: Ref<boolean>
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refresh: (opts?: RefreshOptions) => Promise<void>
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error: Ref<ErrorT | null>
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}
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```
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## Params
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* **key**: a unique key to ensure that data fetching can be properly de-duplicated across requests. If you do not provide a key, then a key that is unique to the file name and line number of the instance of `useAsyncData` will be generated for you.
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* **handler**: an asynchronous function that returns a value
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* **options**:
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* _lazy_: whether to resolve the async function after loading the route, instead of blocking client-side navigation (defaults to `false`)
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* _default_: a factory function to set the default value of the data, before the async function resolves - particularly useful with the `lazy: true` option
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* _server_: whether to fetch the data on the server (defaults to `true`)
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* _transform_: a function that can be used to alter `handler` function result after resolving
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* _pick_: only pick specified keys in this array from the `handler` function result
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* _watch_: watch reactive sources to auto-refresh
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* _initialCache_: When set to `false`, will skip payload cache for initial fetch. (defaults to `true`)
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Under the hood, `lazy: false` uses `<Suspense>` to block the loading of the route before the data has been fetched. Consider using `lazy: true` and implementing a loading state instead for a snappier user experience.
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## Return Values
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* **data**: the result of the asynchronous function that is passed in
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* **pending**: a boolean indicating whether the data is still being fetched
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* **refresh**: a function that can be used to refresh the data returned by the `handler` function
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* **error**: an error object if the data fetching failed
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By default, Nuxt waits until a `refresh` is finished before it can be executed again.
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::alert{type=warning}
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If you have not fetched data on the server (for example, with `server: false`), then the data _will not_ be fetched until hydration completes. This means even if you await `useAsyncData` on the client side, `data` will remain `null` within `<script setup>`.
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::
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## Example
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```ts
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const { data, pending, error, refresh } = await useAsyncData(
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'mountains',
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() => $fetch('https://api.nuxtjs.dev/mountains')
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)
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```
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::ReadMore{link="/guide/features/data-fetching"}
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::
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