Angular Debouncing Guide

Debouncing delays a function until calls have stopped for a configured amount of time. Each new call restarts the timer. With the default settings, only the most recent call executes, using its arguments.

Use debouncing when intermediate calls can be discarded and the final value is what matters. Search inputs, form validation, autosave, and resize handling are common examples.

How debouncing works#

The timeline below shows calls arriving in bursts. Every call resets the timer. The final call in each burst executes after three ticks of inactivity.

Debouncing (wait: 3 ticks)
Timeline: [1 second per tick]
Calls:        ⬇️  ⬇️  ⬇️  ⬇️  ⬇️     ⬇️  ⬇️  ⬇️  ⬇️               ⬇️  ⬇️
Executed:     ❌  ❌  ❌  ❌  ❌     ❌  ❌  ❌  ⏳   ->   ✅     ❌  ⏳   ->   ✅
             [================================================================]
                                                       ^ Executes here after
                                                         3 ticks of no calls

             [Burst of calls]     [More calls]   [Wait]      [New burst]
             No execution         Resets timer   Execute     Reset and execute

Only the latest call in each burst executes. All earlier calls are discarded.

Debouncing is intentionally lossy. If every operation must run, use queuing instead.

When to use debouncing#

Choose debouncing when:

• You want to wait until activity stops.
• Only the latest arguments matter.
• Repeating the operation for every event would waste work.
• A short delay is acceptable.

Choose another utility when:

• Work should run at a steady interval while activity continues. Use throttling.
• A fixed number of calls may run within a time window. Use rate limiting.
• Every operation must eventually run. Use queuing.
• Several items should be processed together. Use batching.
• You need to await a result, handle errors, retry, or abort in-flight work. Use async debouncing.

Choose an API#

• injectDebouncedSignal or injectDebouncedValue for delayed signals
• injectDebouncer for lifecycle methods and selected state

Use the instance's maybeExecute method for event handlers, and state or value helpers for delayed UI state. Keep the instance for cancellation, flushing, selected state, and dynamic options.

Angular example#

import { injectDebouncer } from '@tanstack/angular-pacer'

export class SearchComponent {
  readonly search = injectDebouncer(runSearch, { wait: 300 })
  readonly saver = injectDebouncer(saveDraft, { wait: 500 }, (state) => ({
    isPending: state.isPending,
  }))

  saveNow() {
    this.saver.flush()
  }
}

The focused snippets later in this guide use injectDebouncer and assume they run inside an Angular injection context.

Execution timing#

The leading and trailing options control which edge of the wait period may execute.

const debouncer = injectDebouncer(saveDraft, {
  wait: 1000,
  leading: true,
  trailing: true,
})

debouncer.maybeExecute('first') // Executes immediately.
debouncer.maybeExecute('second')
debouncer.maybeExecute('latest') // Executes after 1 second of inactivity.

With both edges enabled, a single call executes only on the leading edge. A trailing execution occurs only when another call arrives during the wait period.

No maximum wait#

injectDebouncer does not provide a maxWait option. A continuous stream of calls can keep postponing a trailing execution indefinitely. Use throttling when work must continue at a bounded interval while calls are still arriving.

Controlling pending work#

The instance API distinguishes between executing, canceling, and resetting pending work.

Flush#

flush() immediately executes the pending trailing call with the most recent arguments. It does nothing when no trailing call is pending.

const debouncer = injectDebouncer(saveDraft, { wait: 1000 })

debouncer.maybeExecute('draft')
debouncer.flush() // Executes saveDraft('draft') now.

Cancel#

cancel() clears the pending timeout without executing the function. It also allows a leading call to execute immediately the next time maybeExecute() is called.

debouncer.maybeExecute('discarded draft')
debouncer.cancel()

Reset#

reset() restores the debouncer's state counters and flags to their defaults. It does not clear an already scheduled timeout. Call cancel() first when you need to discard pending work and reset state.

debouncer.cancel()
debouncer.reset()

Configuring behavior at runtime#

Use an options function to read reactive configuration:

import { signal } from '@angular/core'

const options = signal({ wait: 500, leading: false, trailing: true })
const debouncer = injectDebouncer(saveDraft, options)

options.set({ wait: 1000, leading: true, trailing: false })

A new wait value applies when the next call schedules a timeout. It does not reschedule a timeout that is already pending. Calling maybeExecute() again clears the old timeout and schedules a new one using the current options.

Enabling and disabling#

Set enabled to false to prevent execution. Disabling a debouncer also cancels its pending call.

const enabled = signal(false)
const debouncer = injectDebouncer(saveDraft, () => ({
  wait: 500,
  enabled: enabled(),
}))

debouncer.maybeExecute('ignored')
enabled.set(true)
debouncer.maybeExecute('saved')

The enabled and wait options may also be functions that receive the debouncer instance:

const debouncer = injectDebouncer(saveDraft, {
  enabled: (debouncer) => debouncer.store.state.executionCount < 10,
  wait: (debouncer) => (debouncer.store.state.executionCount === 0 ? 300 : 500),
})

Observing executions#

Use onExecute for a side effect after the wrapped function runs. The callback receives the executed arguments followed by the debouncer instance.

const debouncer = injectDebouncer(saveDraft, {
  wait: 500,
  onExecute: (args, debouncer) => {
    console.log('Saved arguments:', args)
    console.log('Execution count:', debouncer.store.state.executionCount)
  },
})

Angular lifecycle#

The adapter cancels pending work when its owner is destroyed. Providing onUnmount replaces that default cleanup, so a custom callback must perform every required lifecycle action. When custom cleanup flushes work, remember that user callbacks can run while the component is being destroyed.

Reactive state#

Pass a selector to expose the state used by your view through state(). Without a selector, state() returns {}:

const debouncer = injectDebouncer(saveDraft, { wait: 500 }, (state) => ({
  isPending: state.isPending,
  executionCount: state.executionCount,
}))

console.log(debouncer.state().isPending, debouncer.state().executionCount)

Option callbacks receive the core utility instance. Read the selected state() signal in templates.

To restore selected state that your app has persisted, pass a partial snapshot through initialState. It is merged with the defaults. Restore only durable fields. Pending timers are not restored.

• isPending: Whether a trailing execution is waiting.
• executionCount: How many times the wrapped function has executed.
• lastArgs: The arguments recorded by the most recent trailing-enabled call. Check isPending before treating them as pending work.
• status: 'disabled', 'idle', or 'pending'.

See the Angular API reference for adapter signatures and the public core reference for complete option and state types.