mirror of
https://github.com/nuxt/nuxt.git
synced 2024-11-15 02:14:44 +00:00
48 lines
1.8 KiB
Markdown
48 lines
1.8 KiB
Markdown
|
---
|
||
|
|
title: "useState"
|
||
|
|
description: The useState composable creates a reactive and SSR-friendly shared state.
|
||
|
|
links:
|
||
|
|
- label: Source
|
||
|
|
icon: i-simple-icons-github
|
||
|
|
to: https://github.com/nuxt/nuxt/blob/main/packages/nuxt/src/app/composables/state.ts
|
||
|
|
size: xs
|
||
|
|
---
|
||
|
|
|
||
|
|
## Usage
|
||
|
|
|
||
|
|
```ts
|
||
|
|
// Create a reactive state and set default value
|
||
|
|
const count = useState('counter', () => Math.round(Math.random() * 100))
|
||
|
|
|
||
|
|
```
|
||
|
|
|
||
|
|
:read-more{to="/docs/getting-started/state-management"}
|
||
|
|
|
||
|
|
::callout
|
||
|
|
Because the data inside `useState` will be serialized to JSON, it is important that it does not contain anything that cannot be serialized, such as classes, functions or symbols.
|
||
|
|
::
|
||
|
|
|
||
|
|
::callout{color="amber" icon="i-ph-warning-duotone"}
|
||
|
|
`useState` is a reserved function name transformed by the compiler, so you should not name your own function `useState`.
|
||
|
|
::
|
||
|
|
|
||
|
|
## Using `shallowRef`
|
||
|
|
|
||
|
|
If you don't need your state to be deeply reactive, you can combine `useState` with [`shallowRef`](https://vuejs.org/api/reactivity-advanced.html#shallowref). This can improve performance when your state contains large objects and arrays.
|
||
|
|
|
||
|
|
```ts
|
||
|
|
const state = useState('my-shallow-state', () => shallowRef({ deep: 'not reactive' }))
|
||
|
|
// isShallow(state) === true
|
||
|
|
```
|
||
|
|
|
||
|
|
## Type
|
||
|
|
|
||
|
|
```ts
|
||
|
|
useState<T>(init?: () => T | Ref<T>): Ref<T>
|
||
|
|
useState<T>(key: string, init?: () => T | Ref<T>): Ref<T>
|
||
|
|
```
|
||
|
|
|
||
|
|
- `key`: A unique key ensuring that data fetching is properly de-duplicated across requests. If you do not provide a key, then a key that is unique to the file and line number of the instance of [`useState`](/docs/api/composables/use-state) will be generated for you.
|
||
|
|
- `init`: A function that provides initial value for the state when not initiated. This function can also return a `Ref`.
|
||
|
|
- `T`: (typescript only) Specify the type of state
|