useDebounceFn

Debounce execution of a function.

See also: useThrottleFn

Debounce is an overloaded waiter: if you keep asking him your requests will be ignored until you stop and give him some time to think about your latest inquiry.


Ported from vueuse/useDebounceFn

Example #

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

Button clicked: 0

Event handler called: 0


  • Svelte 
<script setup lang="ts">
	import { Button } from 'flowbite-svelte'
	import { useDebounceFn } from 'sveltuse'

	let updated = 0
	let clicked = 0

	const debouncedFn = useDebounceFn(
		() => {
			updated += 1
		},
		1000,
		{ maxWait: 5000 }
	)

	function clickedFn() {
		clicked += 1
		debouncedFn()
	}
</script>

<div>
	<note>
		Delay is set to 1000ms and maxWait is set to 5000ms for this demo.
	</note>
	<p>Button clicked: {clicked}</p>
	<p>Event handler called: {updated}</p>
	<br />
	<Button on:click={clickedFn}>Smash me!</Button>
</div>

Usage #

import { useDebounceFn } from 'sveltuse'

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

window.addEventListener('resize', debouncedFn)

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

import { useDebounceFn } from 'sveltuse'

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

window.addEventListener('resize', debouncedFn)

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

import { useDebounceFn } from 'sveltuse'

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

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

// or use async/await
async function doRequest() {
  const value = await debouncedRequest()
  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 'sveltuse'

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

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

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

Recommended Reading #

Source #

Source • Demo • Docs
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