TanStack
Pacer v0v0
Getting Started

Vue Quick Start

TanStack Pacer controls when your functions run. The Vue adapter, @tanstack/vue-pacer, wraps each Pacer utility in a composable. Call composables during component setup or inside an active effect scope. The utility cleans up when the scope is disposed and exposes the state you select as a ref.

This page starts with a debounced search input, then covers the patterns most apps need next.

Installation

sh
npm install @tanstack/vue-pacer
npm install @tanstack/vue-pacer

The adapter re-exports everything from @tanstack/pacer, so you do not need to install the core package. See Installation for other package managers.

Your first debouncer

The component below is complete. The input updates on every keystroke. debouncedQuery updates 500 ms after the user stops typing.

vue
<script setup lang="ts">
import { ref } from 'vue'
import { useDebouncedValue } from '@tanstack/vue-pacer'

const query = ref('')
const [debouncedQuery] = useDebouncedValue(query, { wait: 500 })
</script>

<template>
  <input v-model="query" placeholder="Search..." />
  <p>Searching for: {{ debouncedQuery }}</p>
</template>
<script setup lang="ts">
import { ref } from 'vue'
import { useDebouncedValue } from '@tanstack/vue-pacer'

const query = ref('')
const [debouncedQuery] = useDebouncedValue(query, { wait: 500 })
</script>

<template>
  <input v-model="query" placeholder="Search..." />
  <p>Searching for: {{ debouncedQuery }}</p>
</template>

useDebouncedValue accepts a ref or a getter such as () => props.query. It returns a read-only ref. Pass debouncedQuery to your data fetching instead of query, and a fast typist sends one request instead of one per keystroke.

Pick a composable

Every utility comes in several shapes. They share one engine and differ in what they hand back to you. For debouncing:

ComposableReturnsUse it when
useDebouncedValue[debouncedValue, debouncer]You already have a ref and want a lagging copy
useDebouncedState[value, setValue, debouncer]You want a ref with a debounced setter
useDebouncerThe debouncer instanceYou need maybeExecute, flush, cancel, or reactive state

The other utilities follow the same naming pattern:

UtilityInstance composableAsync instance composableGuide
DebouncinguseDebounceruseAsyncDebouncerDebouncing
ThrottlinguseThrottleruseAsyncThrottlerThrottling
Rate limitinguseRateLimiteruseAsyncRateLimiterRate Limiting
QueuinguseQueueruseAsyncQueuerQueuing
BatchinguseBatcheruseAsyncBatcherBatching

Not sure which utility you need? Read Which Pacer Utility Should I Choose?.

Common patterns

Control the debouncer directly

useDebouncer returns the instance. Call maybeExecute from your event handler, and use flush or cancel when the user acts before the timer fires.

vue
<script setup lang="ts">
import { ref } from 'vue'
import { useDebouncer } from '@tanstack/vue-pacer'

const draft = ref('')

const saver = useDebouncer(
  (text: string) => saveDraft(text),
  { wait: 1000 },
  (state) => ({ isPending: state.isPending }),
)
const saverState = saver.state

function onInput(event: Event) {
  draft.value = (event.target as HTMLTextAreaElement).value
  saver.maybeExecute(draft.value)
}
</script>

<template>
  <textarea :value="draft" @input="onInput" />
  <button @click="saver.flush()">Save now</button>
  <button @click="saver.cancel()">Discard</button>
  <p v-if="saverState.isPending">Unsaved changes...</p>
</template>
<script setup lang="ts">
import { ref } from 'vue'
import { useDebouncer } from '@tanstack/vue-pacer'

const draft = ref('')

const saver = useDebouncer(
  (text: string) => saveDraft(text),
  { wait: 1000 },
  (state) => ({ isPending: state.isPending }),
)
const saverState = saver.state

function onInput(event: Event) {
  draft.value = (event.target as HTMLTextAreaElement).value
  saver.maybeExecute(draft.value)
}
</script>

<template>
  <textarea :value="draft" @input="onInput" />
  <button @click="saver.flush()">Save now</button>
  <button @click="saver.cancel()">Discard</button>
  <p v-if="saverState.isPending">Unsaved changes...</p>
</template>

Select the state you render

The third argument is a selector. saver.state is a ref, so read saver.state.value in script. Without a selector, it holds {} and never changes. Select only the fields you render.

Vue templates unwrap top-level refs only. saver.state.isPending in a template reads a property of the ref object, not of its value. Assign the ref to a top-level variable, as saverState does above.

To read state in one part of the template without a selector on the utility, use the Subscribe component. Its slot receives the selected state, and the owning component does not re-render:

vue
<saver.Subscribe
  :selector="(state) => ({ isPending: state.isPending })"
  v-slot="{ isPending }"
>
  <span v-if="isPending">Saving...</span>
</saver.Subscribe>
<saver.Subscribe
  :selector="(state) => ({ isPending: state.isPending })"
  v-slot="{ isPending }"
>
  <span v-if="isPending">Saving...</span>
</saver.Subscribe>

Each utility's guide lists the state fields it exposes.

Make options reactive

A plain options object is read once. To make an option follow a ref or a prop, pass a factory that returns the options:

ts
const props = defineProps<{ wait: number }>()

const debouncer = useDebouncer(search, () => ({ wait: props.wait }))
const props = defineProps<{ wait: number }>()

const debouncer = useDebouncer(search, () => ({ wait: props.wait }))

Property getters such as get wait() { return props.wait } work too. A ref placed inside a plain options object is not unwrapped.

When an option changes, the adapter updates the same utility. Pending work and state survive. A changed wait applies to the next call. It does not reschedule a timer that is already running. Setting enabled to false cancels pending work. key, initialState, and initialItems apply only when the utility is created.

Run async work

The async composables await your function, track execution state, and report errors. This search debounces the request and shows a loading state:

vue
<script setup lang="ts">
import { ref } from 'vue'
import { useAsyncDebouncer } from '@tanstack/vue-pacer'

const results = ref<Array<SearchResult>>([])

const searcher = useAsyncDebouncer(
  async (term: string) => {
    const data = await fetchSearchResults(term)
    results.value = data
    return data
  },
  {
    wait: 300,
    onError: (error) => console.error('Search failed:', error),
  },
  (state) => ({ isExecuting: state.isExecuting }),
)
const searcherState = searcher.state
</script>

<template>
  <input
    @input="searcher.maybeExecute(($event.target as HTMLInputElement).value)"
  />
  <p v-if="searcherState.isExecuting">Loading...</p>
  <ul>
    <li v-for="result in results" :key="result.id">{{ result.title }}</li>
  </ul>
</template>
<script setup lang="ts">
import { ref } from 'vue'
import { useAsyncDebouncer } from '@tanstack/vue-pacer'

const results = ref<Array<SearchResult>>([])

const searcher = useAsyncDebouncer(
  async (term: string) => {
    const data = await fetchSearchResults(term)
    results.value = data
    return data
  },
  {
    wait: 300,
    onError: (error) => console.error('Search failed:', error),
  },
  (state) => ({ isExecuting: state.isExecuting }),
)
const searcherState = searcher.state
</script>

<template>
  <input
    @input="searcher.maybeExecute(($event.target as HTMLInputElement).value)"
  />
  <p v-if="searcherState.isExecuting">Loading...</p>
  <ul>
    <li v-for="result in results" :key="result.id">{{ result.title }}</li>
  </ul>
</template>

maybeExecute returns a promise that resolves with your function's result. The async utilities also support retries and cancellation through an AbortSignal. See the Async Debouncing Guide.

Limit how often an action runs

A rate limiter allows a fixed number of calls per window and rejects the rest:

vue
<script setup lang="ts">
import { useRateLimiter } from '@tanstack/vue-pacer'

const limiter = useRateLimiter(
  (message: string) => sendMessage(message),
  {
    limit: 5,
    window: 60_000,
    onReject: (limiter) =>
      alert(`Slow down. Try again in ${limiter.getMsUntilNextWindow()} ms.`),
  },
  (state) => ({ rejectionCount: state.rejectionCount }),
)
const limiterState = limiter.state
</script>

<template>
  <button @click="limiter.maybeExecute('Hello')">Send</button>
  <p>Rejected: {{ limiterState.rejectionCount }}</p>
</template>
<script setup lang="ts">
import { useRateLimiter } from '@tanstack/vue-pacer'

const limiter = useRateLimiter(
  (message: string) => sendMessage(message),
  {
    limit: 5,
    window: 60_000,
    onReject: (limiter) =>
      alert(`Slow down. Try again in ${limiter.getMsUntilNextWindow()} ms.`),
  },
  (state) => ({ rejectionCount: state.rejectionCount }),
)
const limiterState = limiter.state
</script>

<template>
  <button @click="limiter.maybeExecute('Hello')">Send</button>
  <p>Rejected: {{ limiterState.rejectionCount }}</p>
</template>

Process items in order

A queuer keeps every item and processes them in order. With useAsyncQueuer, concurrency sets how many run at once:

vue
<script setup lang="ts">
import { useAsyncQueuer } from '@tanstack/vue-pacer'

const queue = useAsyncQueuer(
  async (file: File) => uploadFile(file),
  { concurrency: 3 },
  (state) => ({ size: state.size, activeItems: state.activeItems }),
)
const queueState = queue.state

function onFiles(event: Event) {
  const files = (event.target as HTMLInputElement).files
  for (const file of files ?? []) queue.addItem(file)
}
</script>

<template>
  <input type="file" multiple @change="onFiles" />
  <p>
    Uploading {{ queueState.activeItems.length }}, waiting
    {{ queueState.size }}
  </p>
</template>
<script setup lang="ts">
import { useAsyncQueuer } from '@tanstack/vue-pacer'

const queue = useAsyncQueuer(
  async (file: File) => uploadFile(file),
  { concurrency: 3 },
  (state) => ({ size: state.size, activeItems: state.activeItems }),
)
const queueState = queue.state

function onFiles(event: Event) {
  const files = (event.target as HTMLInputElement).files
  for (const file of files ?? []) queue.addItem(file)
}
</script>

<template>
  <input type="file" multiple @change="onFiles" />
  <p>
    Uploading {{ queueState.activeItems.length }}, waiting
    {{ queueState.size }}
  </p>
</template>

Set default options

PacerProvider sets default options for every Pacer composable in its subtree. Options passed to a composable override the defaults.

vue
<script setup lang="ts">
import { PacerProvider } from '@tanstack/vue-pacer'
</script>

<template>
  <PacerProvider
    :default-options="{
      debouncer: { wait: 500 },
      asyncQueuer: { concurrency: 3 },
      rateLimiter: { limit: 5, window: 60_000 },
    }"
  >
    <AppContent />
  </PacerProvider>
</template>
<script setup lang="ts">
import { PacerProvider } from '@tanstack/vue-pacer'
</script>

<template>
  <PacerProvider
    :default-options="{
      debouncer: { wait: 500 },
      asyncQueuer: { concurrency: 3 },
      rateLimiter: { limit: 5, window: 60_000 },
    }"
  >
    <AppContent />
  </PacerProvider>
</template>

To set defaults from a component's setup without a wrapper, call providePacerOptions with the same object or a factory that returns it.

To share options between specific composables instead, define them once with an option helper. Helpers such as debouncerOptions return the object you pass in, typed for that utility:

ts
import { debouncerOptions, useDebouncer } from '@tanstack/vue-pacer'

const searchOptions = debouncerOptions({ wait: 500, leading: false })

const debouncer = useDebouncer(search, { ...searchOptions, key: 'search' })
import { debouncerOptions, useDebouncer } from '@tanstack/vue-pacer'

const searchOptions = debouncerOptions({ wait: 500, leading: false })

const debouncer = useDebouncer(search, { ...searchOptions, key: 'search' })

Control cleanup

When the scope is disposed, debouncers, throttlers, and batchers cancel pending work, and queuers stop processing. Async utilities also abort active work. To keep work instead, pass onUnmount. It replaces the default cleanup:

ts
const saver = useDebouncer(saveDraft, {
  wait: 1000,
  onUnmount: (debouncer) => debouncer.flush(),
})
const saver = useDebouncer(saveDraft, {
  wait: 1000,
  onUnmount: (debouncer) => debouncer.flush(),
})

Set up devtools

Install the devtools packages:

sh
npm install @tanstack/vue-devtools @tanstack/vue-pacer-devtools
npm install @tanstack/vue-devtools @tanstack/vue-pacer-devtools

Render the devtools once in your root component:

vue
<script setup lang="ts">
import { TanStackDevtools } from '@tanstack/vue-devtools'
import { pacerDevtoolsPlugin } from '@tanstack/vue-pacer-devtools'

const dev = import.meta.env.DEV
const plugins = [pacerDevtoolsPlugin()]
</script>

<template>
  <AppContent />
  <TanStackDevtools v-if="dev" :plugins="plugins" />
</template>
<script setup lang="ts">
import { TanStackDevtools } from '@tanstack/vue-devtools'
import { pacerDevtoolsPlugin } from '@tanstack/vue-pacer-devtools'

const dev = import.meta.env.DEV
const plugins = [pacerDevtoolsPlugin()]
</script>

<template>
  <AppContent />
  <TanStackDevtools v-if="dev" :plugins="plugins" />
</template>

A utility appears in the Pacer panel only when you give it a key option. See Devtools for production builds.

Next steps

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