useAsyncData

Within your pages, components, and plugins you can use useAsyncData to get access to data that resolves asynchronously.

Usage

<script setup lang="ts">
const { data, status, error, refresh, clear } = await useAsyncData(
  'mountains',
  () => $fetch('https://api.nuxtjs.dev/mountains')
)
</script>

Watch Params

The built-in watch option allows automatically rerunning the fetcher function when any changes are detected.

<script setup lang="ts">
const page = ref(1)
const { data: posts } = await useAsyncData(
  'posts',
  () => $fetch('https://fakeApi.com/posts', {
    params: {
      page: page.value
    }
  }), {
    watch: [page]
  }
)
</script>

Params

• 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.
• handler: an asynchronous function that must return a truthy value (for example, it should not be undefined or null) or the request may be duplicated on the client side.
  The handler function should be side-effect free to ensure predictable behavior during SSR and CSR hydration. If you need to trigger side effects, use the callOnce utility to do so.
• options:
  • server: whether to fetch the data on the server (defaults to true)
  • lazy: whether to resolve the async function after loading the route, instead of blocking client-side navigation (defaults to false)
  • immediate: when set to false, will prevent the request from firing immediately. (defaults to true)
  • default: a factory function to set the default value of the data, before the async function resolves - useful with the lazy: true or immediate: false option
  • transform: a function that can be used to alter handler function result after resolving
  • getCachedData: Provide a function which returns cached data. A null or undefined return value will trigger a fetch. By default, this is:

    const getDefaultCachedData = (key, nuxtApp) => nuxtApp.isHydrating 
      ? nuxtApp.payload.data[key] 
      : nuxtApp.static.data[key]
    

    Which only caches data when experimental.payloadExtraction of nuxt.config is enabled.
  • pick: only pick specified keys in this array from the handler function result
  • watch: watch reactive sources to auto-refresh
  • deep: return data in a deep ref object (it is true by default). It can be set to false to return data in a shallow ref object, which can improve performance if your data does not need to be deeply reactive.
  • dedupe: avoid fetching same key more than once at a time (defaults to cancel). Possible options:
    • cancel - cancels existing requests when a new one is made
    • defer - does not make new requests at all if there is a pending request

Return Values

• data: the result of the asynchronous function that is passed in.
• refresh/execute: a function that can be used to refresh the data returned by the handler function.
• error: an error object if the data fetching failed.
• status: a string indicating the status of the data request:
  • idle: when the request has not started, such as:
    • when execute has not yet been called and { immediate: false } is set
    • when rendering HTML on the server and { server: false } is set
  • pending: the request is in progress
  • success: the request has completed successfully
  • error: the request has failed
• clear: a function which will set data to undefined, set error to null, set status to 'idle', and mark any currently pending requests as cancelled.

By default, Nuxt waits until a refresh is finished before it can be executed again.

Type

function useAsyncData<DataT, DataE>(
  handler: (nuxtApp?: NuxtApp) => Promise<DataT>,
  options?: AsyncDataOptions<DataT>
): AsyncData<DataT, DataE>
function useAsyncData<DataT, DataE>(
  key: string,
  handler: (nuxtApp?: NuxtApp) => Promise<DataT>,
  options?: AsyncDataOptions<DataT>
): Promise<AsyncData<DataT, DataE>>

type AsyncDataOptions<DataT> = {
  server?: boolean
  lazy?: boolean
  immediate?: boolean
  deep?: boolean
  dedupe?: 'cancel' | 'defer'
  default?: () => DataT | Ref<DataT> | null
  transform?: (input: DataT) => DataT | Promise<DataT>
  pick?: string[]
  watch?: WatchSource[]
  getCachedData?: (key: string, nuxtApp: NuxtApp) => DataT | undefined
}

type AsyncData<DataT, ErrorT> = {
  data: Ref<DataT | null>
  refresh: (opts?: AsyncDataExecuteOptions) => Promise<void>
  execute: (opts?: AsyncDataExecuteOptions) => Promise<void>
  clear: () => void
  error: Ref<ErrorT | null>
  status: Ref<AsyncDataRequestStatus>
};

interface AsyncDataExecuteOptions {
  dedupe?: 'cancel' | 'defer'
}

type AsyncDataRequestStatus = 'idle' | 'pending' | 'success' | 'error'