useDebounceFn

Demo

Delay is set to 1000ms and maxWait is set to 5000ms for this demo.

Pending: false

Button clicked: 0

Event handler called: 0

Usage

import { useDebounceFn
, useEventListener
 } from '@vueuse/core'

const debouncedFn
 = useDebounceFn
(() => {
  // do something
}, 1000)

useEventListener
(window
, 'resize', debouncedFn
)

You can also pass a 3rd parameter to this, with a maximum wait time, similar to lodash debounce

import { useDebounceFn
, useEventListener
 } from '@vueuse/core'

// If no invokation after 5000ms due to repeated input,
// the function will be called anyway.
const debouncedFn
 = useDebounceFn
(() => {
  // do something
}, 1000, { maxWait
: 5000 })

useEventListener
(window
, 'resize', debouncedFn
)

Optionally, you can get the return value of the function using promise operations.

import { useDebounceFn
 } from '@vueuse/core'

const debouncedFn
 = useDebounceFn
(() => 'response', 1000)

debouncedFn
().then
((value
) => {
  console
.log
(value
) // 'response'
})

// or use async/await
async function doRequest
() {
  const value
 = await debouncedFn
()
  console
.log
(value
) // 'response'
}

Since unhandled rejection error is quite annoying when developer doesn't need the return value, the promise will NOT be rejected if the function is canceled by default. You need to specify the option rejectOnCancel: true to capture the rejection.

import { useDebounceFn
 } from '@vueuse/core'

const debouncedFn
 = useDebounceFn
(() => 'response', 1000, { rejectOnCancel
: true })

debouncedFn
()
  .then
((value
) => {
    // do something
  })
  .catch
(() => {
    // do something when canceled
  })

// calling it again will cancel the previous request and gets rejected
setTimeout
(debouncedFn
, 500)

Cancel

You can cancel any pending execution by calling the cancel method.

import { useDebounceFn
 } from '@vueuse/core'

const debouncedFn
 = useDebounceFn
(() => {
  // do something
}, 1000)

debouncedFn
()

// Cancel the pending execution before it runs
debouncedFn
.cancel
()

This is useful when you need to prevent the debounced function from executing, for example, when a component is unmounted or when user input changes context.

Pending State

You can check if there's a pending execution using the isPending ref.

import { useDebounceFn
 } from '@vueuse/core'

const debouncedFn
 = useDebounceFn
(() => {
  // do something
}, 1000)

debouncedFn
()
console
.log
(debouncedFn
.isPending
.value
) // true

// After debounce time elapses or cancel is called
console
.log
(debouncedFn
.isPending
.value
) // false

This is useful for showing loading indicators or disabling UI elements while waiting for the debounced function to execute.

Flush

You can immediately execute the pending invocation using the flush method.

import { useDebounceFn
 } from '@vueuse/core'

const debouncedFn
 = useDebounceFn
(() => {
  // do something
}, 1000)

debouncedFn
()

// Execute the pending invocation immediately instead of waiting
debouncedFn
.flush
()

This is useful when you need to ensure the debounced function runs right away, for example, before navigating away from a page or submitting a form.

Type Declarations

export type UseDebounceFnReturn
<T
 extends FunctionArgs
> =
  CancelablePromisifyFn
<T
>
/**
 * Debounce execution of a function.
 *
 * @see https://vueuse.org/useDebounceFn
 * @param  fn          A function to be executed after delay milliseconds debounced.
 * @param  ms          A zero-or-greater delay in milliseconds. For event callbacks, values around 100 or 250 (or even higher) are most useful.
 * @param  options     Options
 *
 * @return A new, debounced, function with isPending, cancel, and flush properties.
 */
export declare function useDebounceFn
<T
 extends FunctionArgs
>(
  fn
: T
,
  ms
?: MaybeRefOrGetter
<number>,
  options
?: DebounceFilterOptions
,
): UseDebounceFnReturn
<T
>