Debouncing Guide

Rate Limiting, Throttling, and Debouncing are three distinct approaches to controlling function execution frequency. Each technique blocks executions differently, making them "lossy" - meaning some function calls will not execute when they are requested to run too frequently. Understanding when to use each approach is crucial for building performant and reliable applications. This guide will cover the Debouncing concepts of TanStack Pacer.

Debouncing Concept

Debouncing is a technique that delays the execution of a function until a specified period of inactivity has occurred. Unlike rate limiting which allows bursts of executions up to a limit, or throttling which ensures evenly spaced executions, debouncing collapses multiple rapid function calls into a single execution that only happens after the calls stop. This makes debouncing ideal for handling bursts of events where you only care about the final state after the activity settles.

Debouncing Visualization

text

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    [Delayed Execute]  [Wait] [Delayed Execute]

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    [Delayed Execute]  [Wait] [Delayed Execute]

When to Use Debouncing

Debouncing is particularly effective when you want to wait for a "pause" in activity before taking action. This makes it ideal for handling user input or other rapidly-firing events where you only care about the final state.

Common use cases include:

Search input fields where you want to wait for the user to finish typing
Form validation that shouldn't run on every keystroke
Window resize calculations that are expensive to compute
Auto-saving drafts while editing content
API calls that should only happen after user activity settles
Any scenario where you only care about the final value after rapid changes

When Not to Use Debouncing

Debouncing might not be the best choice when:

You need guaranteed execution over a specific time period (use throttling instead)
You can't afford to miss any executions (use queueing instead)

Debouncing in TanStack Pacer

TanStack Pacer provides both synchronous and asynchronous debouncing through the Debouncer and AsyncDebouncer classes respectively (and their corresponding debounce and asyncDebounce functions).

Basic Usage with debounce

The debounce function is the simplest way to add debouncing to any function:

import { debounce } from '@tanstack/pacer'

// Debounce search input to wait for user to stop typing
const debouncedSearch = debounce(
  (searchTerm: string) => performSearch(searchTerm),
  {
    wait: 500, // Wait 500ms after last keystroke
  }
)

searchInput.addEventListener('input', (e) => {
  debouncedSearch(e.target.value)
})

import { debounce } from '@tanstack/pacer'

// Debounce search input to wait for user to stop typing
const debouncedSearch = debounce(
  (searchTerm: string) => performSearch(searchTerm),
  {
    wait: 500, // Wait 500ms after last keystroke
  }
)

searchInput.addEventListener('input', (e) => {
  debouncedSearch(e.target.value)
})

Advanced Usage with Debouncer Class

For more control over the debouncing behavior, you can use the Debouncer class directly:

import { Debouncer } from '@tanstack/pacer'

const searchDebouncer = new Debouncer(
  (searchTerm: string) => performSearch(searchTerm),
  { wait: 500 }
)

// Get information about current state
console.log(searchDebouncer.getExecutionCount()) // Number of successful executions

// Update options dynamically
searchDebouncer.setOptions({ wait: 1000 }) // Increase wait time

// Cancel pending execution
searchDebouncer.cancel()

import { Debouncer } from '@tanstack/pacer'

const searchDebouncer = new Debouncer(
  (searchTerm: string) => performSearch(searchTerm),
  { wait: 500 }
)

// Get information about current state
console.log(searchDebouncer.getExecutionCount()) // Number of successful executions

// Update options dynamically
searchDebouncer.setOptions({ wait: 1000 }) // Increase wait time

// Cancel pending execution
searchDebouncer.cancel()

Leading and Trailing Executions

The synchronous debouncer supports both leading and trailing edge executions:

const debouncedFn = debounce(fn, {
  wait: 500,
  leading: true,   // Execute on first call
  trailing: true,  // Execute after wait period
})

const debouncedFn = debounce(fn, {
  wait: 500,
  leading: true,   // Execute on first call
  trailing: true,  // Execute after wait period
})

leading: true - Function executes immediately on first call
leading: false (default) - First call starts the wait timer
trailing: true (default) - Function executes after wait period
trailing: false - No execution after wait period

Common patterns:

{ leading: false, trailing: true } - Default, execute after wait
{ leading: true, trailing: false } - Execute immediately, ignore subsequent calls
{ leading: true, trailing: true } - Execute on both first call and after wait

Enabling/Disabling

The Debouncer class supports enabling/disabling via the enabled option. Using the setOptions method, you can enable/disable the debouncer at any time:

const debouncer = new Debouncer(fn, { wait: 500, enabled: false }) // Disable by default
debouncer.setOptions({ enabled: true }) // Enable at any time

const debouncer = new Debouncer(fn, { wait: 500, enabled: false }) // Disable by default
debouncer.setOptions({ enabled: true }) // Enable at any time

If you are using a framework adapter where the debouncer options are reactive, you can set the enabled option to a conditional value to enable/disable the debouncer on the fly:

const debouncer = useDebouncer(
  setSearch, 
  { wait: 500, enabled: searchInput.value.length > 3 } // Enable/disable based on input length IF using a framework adapter that supports reactive options
)

const debouncer = useDebouncer(
  setSearch, 
  { wait: 500, enabled: searchInput.value.length > 3 } // Enable/disable based on input length IF using a framework adapter that supports reactive options
)

However, if you are using the debounce function or the Debouncer class directly, you must use the setOptions method to change the enabled option, since the options that are passed are actually passed to the constructor of the Debouncer class.

Asynchronous Debouncing

For async functions or when you need error handling, use the AsyncDebouncer or asyncDebounce:

import { asyncDebounce } from '@tanstack/pacer'

const debouncedSearch = asyncDebounce(
  async (searchTerm: string) => {
    const results = await fetchSearchResults(searchTerm)
    updateUI(results)
  },
  {
    wait: 500,
    onError: (error) => {
      console.error('Search failed:', error)
    }
  }
)

// Will only make one API call after typing stops
searchInput.addEventListener('input', async (e) => {
  await debouncedSearch(e.target.value)
})

import { asyncDebounce } from '@tanstack/pacer'

const debouncedSearch = asyncDebounce(
  async (searchTerm: string) => {
    const results = await fetchSearchResults(searchTerm)
    updateUI(results)
  },
  {
    wait: 500,
    onError: (error) => {
      console.error('Search failed:', error)
    }
  }
)

// Will only make one API call after typing stops
searchInput.addEventListener('input', async (e) => {
  await debouncedSearch(e.target.value)
})

For most use cases, the normal non-async Debouncer is sufficient, but when you need error handling or want to properly handle Promise-based operations, then the async AsyncDebouncer is for you.

The async version provides:

Promise-based execution tracking
Error handling through onError callback
Proper cleanup of pending async operations
Awaitable maybeExecute method

Framework Adapters

Each framework adapter builds convenient hooks and functions around the debouncer classes. Hooks like useDebouncedCallback, useDebouncedState, or useDebouncedValue are small wrappers that can cut down on the boilerplate needed in your own code for some common use cases.