Nuxt/docs/content/3.docs/1.usage/1.data-fetching.md

Data Fetching

Nuxt provides useFetch and useAsyncData to handle data fetching within your application.

useAsyncData

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

Usage

useAsyncData(key: string, fn: () => Object, options?: { defer: boolean, server: boolean })

• key: a unique key to ensure that data fetching can be properly de-duplicated across requests
• fn an asynchronous function that returns a value.
• options:
  • defer: whether to load the route before resolving the async function (defaults to false)
  • server: whether the fetch the data on server-side (defaults to true)
  • transform: A function that can be used to alter fn result after resolving
  • pick: Only pick specified keys in this array from fn result

Under the hood, defer: false uses <Suspense> to block the loading of the route before the data has been fetched. Consider using defer: true and implementing a loading state instead for a snappier user experience.

Example

let counter = 0
export default () => {
  counter++
  return JSON.stringify(counter)
}

<script setup>
const { data } = await useAsyncData('count', () => $fetch('/api/count'))
</script>

<template>
  Page visits: {{ data }}
</template>

useFetch

Within your pages, components and plugins you can use useFetch to get universally fetch from any URL.

This composable provides a convenient wrapper around useAsyncData and $fetch and automatically generates a key based on url and fetch options and infers API response type.

Usage:

useFetch(url: string, options?)

Available options:

• key: Provide a custom key
• Options from ohmyfetch
  • method: Request method
  • params: Query params
  • baseURL: Base URL for request
• Options from useAsyncDaa
  • defer
  • server
  • pick
  • transform

Example

<script setup>
const { data } = await useFetch('/api/count')
</script>

<template>
  Page visits: {{ data.count }}
</template>

Best practices

As seen in Concepts > Data fetching, the data returned by useAsyncData will be stored inside the page payload. This mean that every key returned that is not used in your component will be added to the payload.

We strongly recommend to only select the keys that you will use in your component.

Imagine that /api/mountains/everest returns the following object:

{
  "title": "Mount Everest",
  "description": "Mount Everest is Earth's highest mountain above sea level, located in the Mahalangur Himal sub-range of the Himalayas. The China–Nepal border runs across its summit point",
  "height": "8,848 m",
  "countries": [
    "China",
    "Nepal"
  ],
  "continent": "Asia",
  "image": "https://upload.wikimedia.org/wikipedia/commons/thumb/f/f6/Everest_kalapatthar.jpg/600px-Everest_kalapatthar.jpg"
}

If you plan to only use title and description in your component, you can select the keys by chaining the result of $fetch or pick option:

<script setup>
const { data: mountain } = await useFetch('/api/mountains/everest', { pick: ['title', 'description'] })
</script>

<template>
  <h1>{{ mountain.title }}</h1>
  <p>{{ mountain.description }}</p>
</template>