usePrevious

类别

Utilities

导出体积

251 B

上次更改

4 months ago

保存 ref 的先前值。

示例

源码 playground (beta)

counter: 1

previous: 0

用法

import { usePrevious
 } from '@vueuse/core'
import { shallowRef
 } from 'vue'

const counter
 = shallowRef
('Hello')
const previous
 = usePrevious
(counter
)

console
.log
(previous
.value
) // undefined

counter
.value
 = 'World'

console
.log
(previous
.value
) // Hello

类型声明

/**
 * 保存 ref 的前一个值。
 *
 * @see   {@link https://vueuse.org/usePrevious}
 */
export declare function usePrevious
<T
>(
  value
: MaybeRefOrGetter
<T
>,
): Readonly
<ShallowRef
<T
 | undefined>>
export declare function usePrevious
<T
>(
  value
: MaybeRefOrGetter
<T
>,
  initialValue
: T
,
): Readonly
<ShallowRef
<T
>>