Nuxt/docs/6.bridge/3.bridge-composition-api.md

title	description
Legacy Composition API	Learn how to migrate to Composition API with Nuxt Bridge.

Nuxt Bridge provides access to Composition API syntax. It is specifically designed to be aligned with Nuxt 3. Because of this, there are a few extra steps to take when enabling Nuxt Bridge, if you have been using the Composition API previously.

Remove Modules

• Remove @vue/composition-api from your dependencies.
• Remove @nuxtjs/composition-api from your dependencies (and from your modules in nuxt.config).

Using @vue/composition-api

If you have been using just @vue/composition-api and not @nuxtjs/composition-api, then things are very straightforward.

1. First, remove the plugin where you are manually registering the Composition API. Nuxt Bridge will handle this for you.

   - import Vue from 'vue'
   - import VueCompositionApi from '@vue/composition-api'
   -
   - Vue.use(VueCompositionApi)
   

2. Otherwise, there is nothing you need to do. However, if you want, you can remove your explicit imports from @vue/composition-api and rely on Nuxt Bridge auto-importing them for you.

Migrating from @nuxtjs/composition-api

Nuxt Bridge implements the Composition API slightly differently from @nuxtjs/composition-api and provides different composables (designed to be aligned with the composables that Nuxt 3 provides).

Because some composables have been removed and don't yet have a replacement, this will be a slightly more complicated process.

Remove @nuxtjs/composition-api/module from your buildModules

You don't have to immediately update your imports yet - Nuxt Bridge will automatically provide a 'shim' for most imports you currently have, to give you time to migrate to the new, Nuxt 3-compatible composables, with the following exceptions:

• withContext has been removed. See below.
• useStatic has been removed. There is no current replacement. Feel free to raise a discussion if you have a use case for this.
• reqRef and reqSsrRef, which were deprecated, have now been removed entirely. Follow the instructions below regarding ssrRef to replace this.

Set bridge.capi

import { defineNuxtConfig } from '@nuxt/bridge'

export default defineNuxtConfig({
  bridge: {
    capi: true,
    nitro: false // If migration to Nitro is complete, set to true
  }
})

For each other composable you are using from @nuxtjs/composition-api, follow the steps below.

useFetch

$fetchState and $fetch have been removed.

const {
- $fetch,
- $fetchState,
+ fetch,
+ fetchState,
} = useFetch(() => { posts.value = await $fetch('/api/posts') })

defineNuxtMiddleware

This was a type-helper stub function that is now removed.

Remove the defineNuxtMiddleware wrapper:

- import { defineNuxtMiddleware } from '@nuxtjs/composition-api`
- export default defineNuxtMiddleware((ctx) => {})
+ export default (ctx) => {}

For typescript support, you can use @nuxt/types:

import type { Middleware } from '@nuxt/types'

export default <Middleware> function (ctx) { }

defineNuxtPlugin

This was a type-helper stub function that is now removed.

You may also keep using Nuxt 2-style plugins, by removing the function (as with defineNuxtMiddleware).

Remove the defineNuxtPlugin wrapper:

- import { defineNuxtPlugin } from '@nuxtjs/composition-api'
- export default defineNuxtPlugin((ctx, inject) => {})
+ export default (ctx, inject) => {}

For typescript support, you can use @nuxt/types:

import type { Plugin } from '@nuxt/types'

export default <Plugin> function (ctx, inject) {}

::alert{type="warning"} While this example is valid, Nuxt 3 introduces a new defineNuxtPlugin function that has a slightly different signature. ::

:ReadMore{link="/docs/guide/directory-structure/plugins#creating-plugins"}

useRouter and useRoute

Nuxt Bridge provides direct replacements for these composables via useRouter and useRoute.

The only key difference is that useRoute no longer returns a computed property.

- import { useRouter, useRoute } from '@nuxtjs/composition-api'

  const router = useRouter()
  const route = useRoute()

- console.log(route.value.path)
+ console.log(route.path)