Nuxt/docs/6.bridge/5.nuxt3-compatible-api.md

title	description
New Composition API	Nuxt Bridge implements composables compatible with Nuxt 3.

By migrating from @nuxtjs/composition-api to the Nuxt 3 compatible API, there will be less rewriting when migrating to Nuxt 3.

ssrRef and shallowSsrRef

These two functions have been replaced with a new composable that works very similarly under the hood: useState.

The key differences are that you must provide a key for this state (which Nuxt generated automatically for ssrRef and shallowSsrRef), and that it can only be called within a Nuxt 3 plugin (which is defined by defineNuxtPlugin) or a component instance. (In other words, you cannot use useState with a global/ambient context, because of the danger of shared state across requests.)

- import { ssrRef } from '@nuxtjs/composition-api'

- const ref1 = ssrRef('initialData')
- const ref2 = ssrRef(() => 'factory function')
+ const ref1 = useState('ref1-key', () => 'initialData')
+ const ref2 = useState('ref2-key', () => 'factory function')
  // accessing the state
  console.log(ref1.value)

Because the state is keyed, you can access the same state from multiple locations, as long as you are using the same key.

You can read more about how to use this composable in the Nuxt 3 docs.

ssrPromise

This function has been removed, and you will need to find an alternative implementation if you were using it. If you have a use case for ssrPromise, please let us know via a discussion.

onGlobalSetup

This function has been removed, but its use cases can be met by using useNuxtApp or useState within defineNuxtPlugin. You can also run any custom code within the setup() function of a layout.

- import { onGlobalSetup } from '@nuxtjs/composition-api'

- export default () => {
-   onGlobalSetup(() => {
+ export default defineNuxtPlugin((nuxtApp) => {
+   nuxtApp.hook('vue:setup', () => {
      // ...
    })
- }
+ })

useStore

In order to access Vuex store instance, you can use useNuxtApp().$store.

- import { useStore } from '@nuxtjs/composition-api`
+ const { $store } = useNuxtApp()

useContext and withContext

You can access injected helpers using useNuxtApp.

- import { useContext } from '@nuxtjs/composition-api`
+ const { $axios } = useNuxtApp()

::callout useNuxtApp() also provides a key called nuxt2Context which contains all the same properties you would normally access from Nuxt 2 context, but it's advised not to use this directly, as it won't exist in Nuxt 3. Instead, see if there is another way to access what you need. (If not, please raise a feature request or discussion.) ::

wrapProperty

This helper function is not provided any more but you can replace it with the following code:

const wrapProperty = (property, makeComputed = true) => () => {
  const vm = getCurrentInstance().proxy
  return makeComputed ? computed(() => vm[property]) : vm[property]
}

useAsync and useFetch

These two composables can be replaced with useLazyAsyncData and useLazyFetch, which are documented in the Nuxt 3 docs. Just like the previous @nuxtjs/composition-api composables, these composables do not block route navigation on the client-side (hence the 'lazy' part of the name).

::callout Note that the API is entirely different, despite similar sounding names. Importantly, you should not attempt to change the value of other variables outside the composable (as you may have been doing with the previous useFetch). ::

::callout{color="amber" icon="i-ph-warning-duotone"} The useLazyFetch must have been configured for Nitro. ::

Migrating to the new composables from useAsync:

<script setup>
- import { useAsync } from '@nuxtjs/composition-api'
- const posts = useAsync(() => $fetch('/api/posts'))
+ const { data: posts } = useLazyAsyncData('posts', () => $fetch('/api/posts'))
+ // or, more simply!
+ const { data: posts } = useLazyFetch('/api/posts')
</script>

Migrating to the new composables from useFetch:

<script setup>
- import { useFetch } from '@nuxtjs/composition-api'
- const posts = ref([])
- const { fetch } = useFetch(() => { posts.value = await $fetch('/api/posts') })
+ const { data: posts, refresh } = useLazyAsyncData('posts', () => $fetch('/api/posts'))
+ // or, more simply!
+ const { data: posts, refresh } = useLazyFetch('/api/posts')
  function updatePosts() {
-   return fetch()
+   return refresh()
  }
</script>

useMeta

In order to interact with vue-meta, you may use useNuxt2Meta, which will work in Nuxt Bridge (but not Nuxt 3) and will allow you to manipulate your meta tags in a vue-meta-compatible way.

<script setup>
- import { useMeta } from '@nuxtjs/composition-api'
  useNuxt2Meta({
    title: 'My Nuxt App',
  })
</script>

You can also pass in computed values or refs, and the meta values will be updated reactively:

<script setup>
const title = ref('my title')
useNuxt2Meta({
  title,
})
title.value = 'new title'
</script>

::callout Be careful not to use both useNuxt2Meta() and the Options API head() within the same component, as behavior may be unpredictable. ::

Nuxt Bridge also provides a Nuxt 3-compatible meta implementation that can be accessed with the useHead composable.

<script setup>
- import { useMeta } from '@nuxtjs/composition-api'
  useHead({
    title: 'My Nuxt App',
  })
</script>

You will also need to enable it explicitly in your nuxt.config:

import { defineNuxtConfig } from '@nuxt/bridge'
export default defineNuxtConfig({
  bridge: {
    meta: true
  }
})

This useHead composable uses @unhead/vue under the hood (rather than vue-meta) to manipulate your <head>. Accordingly, it is recommended not to use both the native Nuxt 2 head() properties as well as useHead , as they may conflict.

For more information on how to use this composable, see the Nuxt 3 docs.

Explicit Imports

Nuxt exposes every auto-import with the #imports alias that can be used to make the import explicit if needed:

<script setup lang="ts">
import { ref, computed } from '#imports'

const count = ref(1)
const double = computed(() => count.value * 2)
</script>

Disabling Auto-imports

If you want to disable auto-importing composables and utilities, you can set imports.autoImport to false in the nuxt.config file.

export default defineNuxtConfig({
  imports: {
    autoImport: false
  }
})

This will disable auto-imports completely but it's still possible to use explicit imports from #imports.