4a3ce4cc1d
Add comprehensive reference documentation for: - Vitest: environments, projects/workspaces, type testing, vi utilities - Pinia: HMR, Nuxt integration, SSR setup - Vue: built-in components (Transition, Teleport, Suspense, KeepAlive) and advanced directives
41 lines
712 B
Markdown
41 lines
712 B
Markdown
---
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category: Utilities
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---
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# usePrevious
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Holds the previous value of a ref.
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## Usage
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```ts
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import { usePrevious } from '@vueuse/core'
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import { shallowRef } from 'vue'
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const counter = shallowRef('Hello')
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const previous = usePrevious(counter)
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console.log(previous.value) // undefined
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counter.value = 'World'
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console.log(previous.value) // Hello
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```
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## Type Declarations
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```ts
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/**
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* Holds the previous value of a ref.
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*
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* @see {@link https://vueuse.org/usePrevious}
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*/
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export declare function usePrevious<T>(
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value: MaybeRefOrGetter<T>,
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): Readonly<ShallowRef<T | undefined>>
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export declare function usePrevious<T>(
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value: MaybeRefOrGetter<T>,
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initialValue: T,
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): Readonly<ShallowRef<T>>
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```
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