mirror of
https://github.com/nuxt/nuxt.git
synced 2024-11-26 23:52:06 +00:00
61 lines
2.1 KiB
Markdown
61 lines
2.1 KiB
Markdown
---
|
|
title: "callOnce"
|
|
description: "Run a given function or block of code once during SSR or CSR."
|
|
navigation:
|
|
badge: New
|
|
links:
|
|
- label: Source
|
|
icon: i-simple-icons-github
|
|
to: https://github.com/nuxt/nuxt/blob/main/packages/nuxt/src/app/composables/once.ts
|
|
size: xs
|
|
---
|
|
|
|
::callout{icon="i-ph-info-duotone" color="blue"}
|
|
This utility is available since [Nuxt v3.9](/blog/v3-9).
|
|
::
|
|
|
|
## Purpose
|
|
|
|
The `callOnce` function is designed to execute a given function or block of code only once during:
|
|
- server-side rendering but not hydration
|
|
- client-side navigation
|
|
|
|
This is useful for code that should be executed only once, such as logging an event or setting up a global state.
|
|
|
|
## Usage
|
|
|
|
```vue [app.vue]
|
|
<script setup>
|
|
const websiteConfig = useState('config')
|
|
|
|
await callOnce(async () => {
|
|
console.log('This will only be logged once')
|
|
websiteConfig.value = await $fetch('https://my-cms.com/api/website-config')
|
|
})
|
|
</script>
|
|
```
|
|
|
|
::callout{to="/docs/getting-started/state-management#usage-with-pinia"}
|
|
`callOnce` is useful in combination with the [Pinia module](/modules/pinia) to call store actions.
|
|
::
|
|
|
|
:read-more{to="/docs/getting-started/state-management"}
|
|
|
|
::callout{color="info" icon="i-ph-warning-duotone"}
|
|
Note that `callOnce` doesn't return anything. You should use [`useAsyncData`](/docs/api/composables/use-async-data) or [`useFetch`](/docs/api/composables/use-fetch) if you want to do data fetching during SSR.
|
|
::
|
|
|
|
::callout
|
|
`callOnce` is a composable meant to be called directly in a setup function, plugin, or route middleware, because it needs to add data to the Nuxt payload to avoid re-calling the function on the client when the page hydrates.
|
|
::
|
|
|
|
## Type
|
|
|
|
```ts
|
|
callOnce(fn?: () => any | Promise<any>): Promise<void>
|
|
callOnce(key: string, fn?: () => any | Promise<any>): Promise<void>
|
|
```
|
|
|
|
- `key`: A unique key ensuring that the code is run once. If you do not provide a key, then a key that is unique to the file and line number of the instance of `callOnce` will be generated for you.
|
|
- `fn`: The function to run once. This function can also return a `Promise` and a value.
|