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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
109 lines
2.7 KiB
Markdown
109 lines
2.7 KiB
Markdown
---
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category: Watch
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alias: throttledWatch
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---
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# watchThrottled
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Throttled watch. The callback will be invoked at most once per specified duration.
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## Usage
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Similar to `watch`, but offering extra options `throttle`, `trailing`, and `leading` which will be applied to the callback function.
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```ts
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import { watchThrottled } from '@vueuse/core'
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watchThrottled(
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source,
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() => { console.log('changed!') },
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{ throttle: 500 },
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)
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```
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### Options
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| Option | Type | Default | Description |
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| ---------- | -------------------------- | ------- | ----------------------------------------- |
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| `throttle` | `MaybeRefOrGetter<number>` | `0` | Throttle interval in ms (can be reactive) |
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| `trailing` | `boolean` | `true` | Invoke on the trailing edge |
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| `leading` | `boolean` | `true` | Invoke on the leading edge |
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All standard `watch` options (`deep`, `immediate`, `flush`, etc.) are also supported.
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### Leading and Trailing
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Control when the callback is invoked:
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```ts
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import { watchThrottled } from '@vueuse/core'
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// Only invoke at the start of each throttle period
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watchThrottled(source, callback, {
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throttle: 500,
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leading: true,
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trailing: false,
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})
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// Only invoke at the end of each throttle period
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watchThrottled(source, callback, {
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throttle: 500,
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leading: false,
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trailing: true,
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})
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```
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## How It Works
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It's essentially a shorthand for the following code:
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```ts
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import { throttleFilter, watchWithFilter } from '@vueuse/core'
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watchWithFilter(
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source,
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() => { console.log('changed!') },
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{
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eventFilter: throttleFilter(500),
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},
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)
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```
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## Type Declarations
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```ts
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export interface WatchThrottledOptions<
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Immediate,
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> extends WatchOptions<Immediate> {
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throttle?: MaybeRefOrGetter<number>
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trailing?: boolean
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leading?: boolean
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}
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export declare function watchThrottled<
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T extends Readonly<MultiWatchSources>,
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Immediate extends Readonly<boolean> = false,
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>(
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sources: [...T],
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cb: WatchCallback<MapSources<T>, MapOldSources<T, Immediate>>,
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options?: WatchThrottledOptions<Immediate>,
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): WatchHandle
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export declare function watchThrottled<
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T,
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Immediate extends Readonly<boolean> = false,
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>(
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source: WatchSource<T>,
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cb: WatchCallback<T, Immediate extends true ? T | undefined : T>,
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options?: WatchThrottledOptions<Immediate>,
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): WatchHandle
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export declare function watchThrottled<
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T extends object,
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Immediate extends Readonly<boolean> = false,
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>(
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source: T,
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cb: WatchCallback<T, Immediate extends true ? T | undefined : T>,
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options?: WatchThrottledOptions<Immediate>,
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): WatchHandle
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/** @deprecated use `watchThrottled` instead */
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export declare const throttledWatch: typeof watchThrottled
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```
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