Passing an empty array as the second argument to useEffect makes it only run on mount and unmount, thus stopping any infinite loops.
useEffect(() => {
setIngredients({});
}, []);
This was clarified to me in the blog post on React hooks at https://www.robinwieruch.de/react-hooks/
Answer from WhiteFluffy on Stack OverflowPassing an empty array as the second argument to useEffect makes it only run on mount and unmount, thus stopping any infinite loops.
useEffect(() => {
setIngredients({});
}, []);
This was clarified to me in the blog post on React hooks at https://www.robinwieruch.de/react-hooks/
Had the same problem. I don't know why they not mention this in docs. Just want to add a little to Tobias Haugen answer.
To run in every component/parent rerender you need to use:
useEffect(() => {
// don't know where it can be used :/
})
To run anything only one time after component mount(will be rendered once) you need to use:
useEffect(() => {
// do anything only one time if you pass empty array []
// keep in mind, that component will be rendered one time (with default values) before we get here
}, [] )
To run anything one time on component mount and on data/data2 change:
const [data, setData] = useState(false)
const [data2, setData2] = useState('default value for first render')
useEffect(() => {
// if you pass some variable, than component will rerender after component mount one time and second time if this(in my case data or data2) is changed
// if your data is object and you want to trigger this when property of object changed, clone object like this let clone = JSON.parse(JSON.stringify(data)), change it clone.prop = 2 and setData(clone).
// if you do like this 'data.prop=2' without cloning useEffect will not be triggered, because link to data object in momory doesn't changed, even if object changed (as i understand this)
}, [data, data2] )
How i use it most of the time:
export default function Book({id}) {
const [book, bookSet] = useState(false)
const loadBookFromServer = useCallback(async () => {
let response = await fetch('api/book/' + id)
response = await response.json()
bookSet(response)
}, [id]) // every time id changed, new book will be loaded
useEffect(() => {
loadBookFromServer()
}, [loadBookFromServer]) // useEffect will run once and when id changes
if (!book) return false //first render, when useEffect did't triggered yet we will return false
return <div>{JSON.stringify(book)}</div>
}
Hey!! First time building a website and have ran into this issue when trying to fetch content from Sanity Studio.
Here's the link: https://pastebin.com/3iL0gpBt
Copying what I think is the relevant part of the code
export default function IssuesList() {
const [items, setItems] = useState([]);
useEffect(() => {
sanityClient
.fetch(
`*[_type == "issue"] | order(publishedAt desc) {
title,
slug,
description,
frontCover{
asset->{
_id,
url
}
}
}`
)
.then((data) => {
setItems(data);
})
.catch(console.error);
});
return (
<div css={issuesListSx}>
<Frame path={[{ name: "Issues", slug: "/issues" }]}>
<Grid gap={2} columns={[1, null, 2]} className="issuesGrid">
{items.map((issue) => {
return (
<div className="issueItem" key={issue.title}>
<Link to={"/issues/" + issue.slug.current}>
<div>{issue.title}</div>
{issue.frontCover && "asset" in issue.frontCover && (
<img src={issue.frontCover.asset.url} alt="" />
)}
</Link>
</div>
);
})}
</Grid>
</Frame>
</div>
);
}E: Fixed!! Had to add an empty array as a second parameter to useEffect
react query select causing useEffect infinite loop
Yet another useEffect()-causing-infinte-loop when fetching from API post. But Whyyyy?
useEffect update on state change without infinite loop?
You're super close! useEffect doesn't always require a dependency. Leave it blank and it'll only load once, similar to componentDidMount. Take a look at the following. In the case to rerun useEffect on state change you'll likely want to use a second state that isn't the state for data or use props from a parent component. Hopefully that'll steer you in the right direction.
useEffect(() => { axios.get('https://example.com/api') .then(res => { setData(res.data); }) .catch(err => { // Handle error }) }, []);
More on reddit.comFetch method in useEffect is in infinite loop - javascript
Videos
Hi,
I read similar Reddit posts, googled a solution but I couldn't figure out why useEffect is doing an infinite loop so I'm hoping that Reddit will help me. Here's a code:
const [posts, setPosts] = useState([]);
const fetchData = async () => {
const response = await fetch(url);
const data = await response.json();
setPosts(data);
console.log(data)
}
useEffect(() => {
fetchData();
}, [posts]);
By looking at the console, I can see that the console.log is called infinitely.
Here's a screenshot of the console. You can see that I'm fetching an array with objects (not an object).
I tried fetch without async/await. Same result.
I know that I won't have an issue if useEffect has an empty dependency array, but I want it to update the results on the page automatically if I create a new post or delete a post (I'm fetching results from my local WordPress).
Not sure why, but I don't think having posts.length as dependency is the right solution.
What am I doing wrong?
The code:
import React, { useState, useEffect } from 'react';
import axios from 'axios';
function Foo() {
const [data, setData] = useState([]);
useEffect(() => {
const fetchData = async () => {
const response = await axios('api_here');
setData(response.data);
};
fetchData();
}, [data]);
return <>{console.log(data)}</>;
}
export default Foo;
Currently, the above snippet results in a infinite loop. I understand why: the culprit is setData(\`response.data``). How can I fix it but still getfetchDatato run on changes to the state living indata? Doing so only when the component is mounted is straightforward, changeuseEffectsecond argument to[]`. But how to run it on state change?
Things I tried:
-
Compare response.data with data and return early if they are equal:
[snip]
const response = await axios('api_here');
if (response.data === data) return;
[snip]No difference, infinite loop.
2. Put object in the state and pass its values to useEffect:
[snip]
const [data, setData] = useState([]);
[snip]
[snip]
fetchData();
}, [Object.values(data)]);
[snip]Infinite loop is still there, and now React is complaining as well:
React Hook useEffect has a missing dependency: 'data'. Either include it or remove the dependency array React Hook useEffect has a complex expression in the dependency array. Extract it to a separate variable so it can be statically checked
3. Using [data.length] instead of [data]:
[snip]
fetchData();
}, [data.length]);
[snip]
The above sort of works - no more infinite loop. But, as I understand it, useEffect will only be re-run if the length of data will change, not necessarily when the values will be modified without altering the length of it. And React is complaining about missing dependency: 'data' as well.
I'm merely beginner in JS / React world and don't have other ideas how to solve this. Any help will be greatly appreciated!
You're super close! useEffect doesn't always require a dependency. Leave it blank and it'll only load once, similar to componentDidMount. Take a look at the following. In the case to rerun useEffect on state change you'll likely want to use a second state that isn't the state for data or use props from a parent component. Hopefully that'll steer you in the right direction.
useEffect(() => { axios.get('https://example.com/api') .then(res => { setData(res.data); }) .catch(err => { // Handle error }) }, []);
Maybe Im missing something, but it looks like you want to fetch new data every time you set the data state. Then you set that fetched data as the state, which triggers the fetch...
What are you trying to accomplish?
Because both setusers, setloading is updating inside the useEffect which causes to fire the useEffect again. Just remove the side Effects from the useEffect array
}, [])
inside of your effect function, when you do setusers(JSON.parse(body)) and setloading(false) you are updating userData to a new array. Even if all the items inside of that new array are exactly the same, the reference to the new userData array has changed, causing the dependencies of the effect to differ, triggering the function again -- ad infinitum.
One simple solution is to simply remove setusers from the dependency array. In this way, the useEffect function basically acts similar to componentDidMount in that it will trigger once and only once when the component first renders.
useEffect(() => {
setloading(true);
fetch("/allotherusers", {credentials: "include"})
.then(response => response.text())
.then(body => {
if (body === '') {
return <Navigate to="/" />
}
else {
setusers(JSON.parse(body));
}
setloading(false);
});
}, [])
I think you should try this.!