Today I'm going to show you how to build a useDebounce React Hook that makes it super easy to debounce API calls to ensure that they don't execute too frequently. I've also put together a demo that uses our hook. It searches the Marvel Comic API and uses useDebounce to prevent API calls from being fired on every keystroke.
Pretty nifty huh? Okay, now on to the code!
First let's figure out how we want our hook to be used and we can let that guide or actual implementation of the hook logic. Rather than debounce the calling of our API request we're going to design this hook to debounce any value within our component's render function. We're then going to combine this with useEffect
to fire off a new API request whenever that input value changes. This code example assumes some familiarity with the useState
and useEffect
hooks, which you can learn about in the React Hook docs.
import React, { useState, useEffect } from 'react';
import useDebounce from './use-debounce';
// Usage
function App() {
// State and setter for search term
const [searchTerm, setSearchTerm] = useState('');
// State and setter for search results
const [results, setResults] = useState([]);
// State for search status (whether there is a pending API request)
const [isSearching, setIsSearching] = useState(false);
// Now we call our hook, passing in the current searchTerm value.
// The hook will only return the latest value (what we passed in) ...
// ... if it's been more than 500ms since it was last called.
// Otherwise, it will return the previous value of searchTerm.
// The goal is to only have the API call fire when user stops typing ...
// ... so that we aren't hitting our API rapidly.
const debouncedSearchTerm = useDebounce(searchTerm, 500);
// Here's where the API call happens
// We use useEffect since this is an asynchronous action
useEffect(
() => {
// Make sure we have a value (user has entered something in input)
if (debouncedSearchTerm) {
// Set isSearching state
setIsSearching(true);
// Fire off our API call
searchCharacters(debouncedSearchTerm).then(results => {
// Set back to false since request finished
setIsSearching(false);
// Set results state
setResults(results);
});
} else {
setResults([]);
}
},
// This is the useEffect input array
// Our useEffect function will only execute if this value changes ...
// ... and thanks to our hook it will only change if the original ...
// value (searchTerm) hasn't changed for more than 500ms.
[debouncedSearchTerm]
);
// Pretty standard UI with search input and results
return (
<div>
<input
placeholder="Search Marvel Comics"
onChange={e => setSearchTerm(e.target.value)}
/>
{isSearching && <div>Searching ...</div>}
{results.map(result => (
<div key={result.id}>
<h4>{result.title}</h4>
<img
src={`${result.thumbnail.path}/portrait_incredible.${
result.thumbnail.extension
}`}
/>
</div>
))}
</div>
);
}
// API search function
function searchCharacters(search) {
const apiKey = 'f9dfb1e8d466d36c27850bedd2047687';
const queryString `apikey=${apiKey}&titleStartsWith=${search}`;
return fetch(
`https://gateway.marvel.com/v1/public/comics?${queryString}`,
{
method: 'GET'
}
)
.then(r => r.json())
.then(r => r.data.results)
.catch(error => {
console.error(error);
return [];
});
}
Okay, so that looks pretty good! Now let's build the actual hook so that our app works.
import React, { useState, useEffect } from 'react';
// Our hook
export default function useDebounce(value, delay) {
// State and setters for debounced value
const [debouncedValue, setDebouncedValue] = useState(value);
useEffect(
() => {
// Set debouncedValue to value (passed in) after the specified delay
const handler = setTimeout(() => {
setDebouncedValue(value);
}, delay);
// Return a cleanup function that will be called every time ...
// ... useEffect is re-called. useEffect will only be re-called ...
// ... if value changes (see the inputs array below).
// This is how we prevent debouncedValue from changing if value is ...
// ... changed within the delay period. Timeout gets cleared and restarted.
// To put it in context, if the user is typing within our app's ...
// ... search box, we don't want the debouncedValue to update until ...
// ... they've stopped typing for more than 500ms.
return () => {
clearTimeout(handler);
};
},
// Only re-call effect if value changes
// You could also add the "delay" var to inputs array if you ...
// ... need to be able to change that dynamically.
[value]
);
return debouncedValue;
}
And there you have it! We now have a debounce hook that we can use to debounce any value right in the body of our component. Debounced values can then be included in useEffect
's input array, instead of the non-debounced values, to limit the frequency of that effect being called.
Also check out my React codebase generator. It will give you a nice UI, auth, database, payments and more. Thousands of React devs use it to build and launch apps quickly.
Discussion (48)
Why not just:
Now you can use this debouce in other hooks.
how do you make the call debounce function ?
nope not working , geting the state value as undefined
Are you able to show your code for the event handler and how you trigger the call?
i have triggered the call in the same way, but it is not working at all ,and state is undefined
My aproach is this way:
This looks great! Could you give us an example on how to implement it?
whilst I like the idea of this, I think the UI and the API call should be far more decoupled, so instead I've went for:
why dont we do this in the useEffect?
i tried this but the cleartimeout was not working, the timeout was not being cleared, i didnt understand the reason.
can anyone explain?
Great article!
I've been using this pattern with hooks lately:
It's clean and works well for most of the cases.
Here's a version
useDebounce
implemented using lodash: github.com/gnbaron/use-lodash-debo...Hereโs my take on a
lodash.debounce
hook. I donโt see why the hook shouldnโt be more convenient to use, so I basically made auseState
wrapper which updates the value immediately (a requirement for controlled inputs), and updates asignal
, which is meant to be used in auseEffect
โs dependency array, only whenever specified as perlodash.debounce
โs docs.Great - thanks! The example would be easier to read if you included all the imports and exports. Great job.
Good call! Just updated the post.
Awesome! :)
Hi,
Thanks for the article. I'm curious about the chosen approch of providing a value to the custom hook that gets updates over time.
Here we listen to
value
changes in the custom hook with the inneruseEffect
and react to changes. Most of the hooks I'm familiar with treat the arguments they get as sort of initialization values that doesn't change overtime or even if changed are not monitored. For exampleuseState, useReducer, useSelector, useMemo, useCallback, useRef
are all hooks that doesn't react to changes of the initial values provided to the hook.I know that your sample works and is valid implementation but I'm sure if it will not confuse developers who read the code. you could easily expose a second argument to update the value which will look very similar to
useState
wdyt?
useCallback
,useSelector
,useMemo
,useReducer
are actually operating on most recent arguments each run.It's only
useState
anduseRef
who purposely ignore any changes on sequential callsHow could you modify this to make it a "leading" debounce?
Hmm this doesn't seem to work if you add text after the initial query (i.e. 'wolverine' as the first full term to debounce, then appending it to become 'wolverine x-men'.. the 'x-men' part doesnt show up until the debouncing times out). I feel like this code is so short and simple I should be able to figure it out, but I can't seem to see why the UI lags so hard on the second set of characters.
Aha, I take it back! Turns out I needed to pull my search input into its own component. Problem solved! (I think)
Thanks for share!
Very helpful, thank you! Years ago I needed something like this and ended up using throttle feature of redux sagas. Not bad, but I try to avoid redux (gets a bit unreadable over time).
I'm writing a new app and needed an "auto-save" feature where a form is auto-saved every x seconds, provided any of the inputs were changed. I started doing my own thing (setTimeout, setInterval) and luckily stumbled on this post. Saved me time. Elegant and it works.
Throttling API calls from UI is a very important technique to learn, I wish Facebook would throw some sort of "autocomplete" or "lookup text field" example where they use your code.
Loved the explanation. Thanks!
Although I would use useRef hook to set the timer variable to reduce the heap memory usage.
Why using
useEffect
for the api call? I don't see any issue with doing async api calls inside a component rendering function.Any side effects should be wrapped in useEffect or within an event handler like onClick. Not sure what could go wrong by inlining it like that, but know itโs heavily discouraged by the React team.
You wrap side effects in useEffect so they don't run on every render. You technically could make a request inside render without wrapping it in useEffect, but it'll happen on every single render, which is usually not what you want.
You typically only want side effects to run when things they care about change, like when some search text changes. That's exactly what useEffect does for you - it helps make sure the side effects only run when they need to.
This reply is great, thanks!
This makes the most since:
import { useCallback, useRef } from 'react'
export default function useDebounce(func, delay = 400) {
let debounce = useRef(null)
return useCallback(
(...args) => {
const context = this
clearTimeout(debounce.current)
debounce.current = setTimeout(() => {
func.apply(context, args)
}, delay)
},
[func],
)
}
Usage:
const handleWindowResize = useDebounce(SetWindow)
useEffect(() => {
window.addEventListener('resize', handleResize)
}, [])
Awesome! I had a similar project and this looked easier than I thought!
This is really elegant! Have you thought about publishing this as a node_module?
This was a great guide, had been struggling for a while with getting something like this to work.
Thanks!
Thanks! Helped me a lot
You've got a missing
=
hereGreat read!
Just as a side note: you don't have to import react to your use-debounce.js.
" import { useState, useEffect } from 'react';"is just fine
Amazing, did not think to have
debouncedValue
instead of debounced version of callback.Probably we better cancel processing in main
useEffect
to avoid race conditions.this is not working, i am getting redundant calls, the function calls are not getting cancelled
Great work, thanks a lot. I want to write a similar post in my native language Bangla, is this ok if i use your post as reference and also your demo project to show how this work ?
Yeah sure! Please just link to my post as well somewhere.
Thank you so much, i will.
thank you, kind sir!
Try to hold down any key and you will see, that searching appears 2 times - after 500 ms after the first character and after 500 ms after the last. How to avoid this glitch?
Very useful. I signed up only to thank you.
Excellent!
Needed this and was struggling a bit myself to get it to work flawlessly...
Thanks!
Very nice code! :) very helpfull
Thank you for sharing that, it's a very useful and simple way.