I'm trying to rerender a component once the state is changed, this how I do it:
const [items, setItems] = useState([]);
useEffect(() => {
console.log("I am rerendering")
const displayNotebook = async () => {
const reponse = await axios({// URL etc...},
});
setItems(reponse.data); // add data to the list
};
displayNotebook()
},[items]);
I pass the date in a map as so
const workspaceCard = items.map((msg) => (
<WorkspaceContent
message={msg.content}
/>));
The problem is that the component is in a infinite rerendering, I could use an empty array but this not what I want, I am trying to rerender the component each time the state is updated.
I searched and found this answer Infinite loop in useEffect but does not help me
As Gaëtan already indicated, your logic has a loop: inside your effect you are setting items, but you are also indicating that the effect should re-run whenever items change. Hence the cycle. The fix is simple then, just remove the dependency on items, if you don't need/want to rerun the effect whenever they change:
useEffect(() => {
// ...
},[]); // items removed
Related
Here is a useEffect hook that I used in reactjs:
Problem: The useEffect calls fetchAllCategories() endlessly. Infact, over 1000 requests until I terminate. I only want it to run on page mount and when I click on the button to change catName state. What could I be doing wrong?
const [catName, setCategories] = useState([]);
const categoryRef = useRef();
useEffect(()=>{
const fetchAllCategories = async () =>{
try{
const res = await axios.get(`${BASE_URL}/category`)
return setCategories(res.data);
}catch(err){
}
}
fetchAllCategories()
}, [catName])
//create new category
const createNewCategory = async ()=>{
const categoryName = {
catName: categoryRef.current.value
}
try{
const response = await axiosPrivate.post(`${BASE_URL}/category`, categoryName, { withCredentials: true,
headers:{authorization: `Bearer ${auth}`}
})
return setCategories([response.data])
}catch(err){
}
}
The button that triggers changes in catName
<button onClick={ createNewCategory} className='button-general'>Create</button>
You trigger the effect to be run on change of catNames, and then change catNames from the effect itself. This results in the endless self-triggering of the effect.
One solution could be to make your effect depend on nothing:
useEffect(() => {
....
}, []);
Thank you all for pointing out the issue to me. Since I now know the issue, I have been able to fix it. All I did was create another state and made the useEffect to depend on it. Then, whenever the button is clicked, I change the state to the opposite of the initial state. This works and doesnt cause endless calls.
If you absolutely need catName as a dependency, this can work for you:
useEffect(() => {
const fetchAllCategories = async () => {
try {
const res = await axios.get(`${BASE_URL}/category`);
return setCategories(res.data);
} catch (err) {}
};
fetchAllCategories();
}, [JSON.stringify(catName)]);
This is happening because you update the catName state inside the useEffect using setCategories(res.data) this keeps triggering your useEffect thus an infinite loop
You programmed it to run endlessly.
REASON
See, this React hook useEffect has two parameters:
Effect, the callback function which is called whenever the component renders.
List of Dependencies on which the useEffect hook depends and re-renders if any such dependency is updated.
Now, in your case, you've passed catName as a dependency, whose state is updated when the button is clicked. This causes useEffect to call the callback function which calls fetchAllCategories() which also update catName. And this causes an endless loop.
SOLUTION
Just remove the dependency from useEffect as:
useEffect(() {
...
}, []);
Now, updating catName won't cause the effect (The Callback function) to be called endlessly.
any idea how to refactor this code so I can be able to simply use firestore snapshot (Realtime data) to update the current state with those changeable data the SetState function simply update the current state with the new data but since i am calling is in useEffect it is triggering a loop can I use callback instead to work around this issue ?
const [data, setData] = useState<any>(null);
useEffect(() => {
let colRef = collection(db, 'Weeks');
const docRef = doc(colRef, context.focus as string);
const unsub = onSnapshot(docRef, (doc) => {
setData(doc.data());
if (doc.data()) {
context.SetState({ arr: doc.data()?.arr });
}
return () => unsub;
});
}, [data]);
remove data from the dependency and the infinate loop will end.
you do not use the data in the useEffect, remember to not useEffect on a state that you use its setter inside that useEffect or you will find yourself in such a situation its kinda like a recusive call without a condition to exit the loop.
I Got Stuck in an infinite loop in react.js. How to resolve this?
useEffect(() => {
fetch("https://react-http-d55a9-default-rtdb.firebaseio.com/todo.json")
.then((response) => {
return response.json();
})
.then((data) => {
console.log(data);
setUsersList((prev) => [...prev]); //cause of infinite loop
});
}, [usersList]);
You are having an infinite loop because your useEffect array of dependencies has usersList on it and at the same time you are updating this variable inside your useEffect function. So your useEffect runs when the component mounts which updates your usersList which makes the useEffect run again which again updates your usersList which makes it run again and so on...
To fix this, remove usersList from the array of dependencies and have an empty array instead: []. If you do this your useEffect will run once, when your component mounts.
The dependency list passed to useEffect determines when the effect should run again. The infinite loop is happening because this effect causes usersList to change, which triggers the effect to run again.
Since this effect doesn't use any other variables, it doesn't need anything in its dependency list:
useEffect(() => {
fetch(...)
// ...
}, []); // leave this empty, so the effect only runs when the component mounts
If your URL depended on a prop or something else, then you want it in the dependency list:
useEffect(() => {
fetch(`https://example.com/todo/${props.id}`)
.then(...)
// Since the URL depends on the id prop, the effect should re-run if it changes
}, [props.id]);
According to question asked, you want the userList to be watched everytime it updates. What we can do is define one more state variable as mentioned in the code as isFetched or if you are using redux you can put that over there, because if we just watch the userList variable then it caughts up in infinite loop as setting the userList is happening in useEffect itself. With the help of isFetched, we can manage when to call the api and whenever the flag is false it calls the api.
Right now in the code i have put one more state variable as setCount, as i didn't know how many times you want to call your api. So you can put your condition there and stop the call when your condition satisfies.
function App() {
const [userList, setUserList] = useState([]);
const [isFetched, setIsFetched] = useState(false);
const [, setCount] = useState(3);
const callApiPending = useCallback(()=>{
fetch("https://react-http-d55a9-default-rtdb.firebaseio.com/todo.json")
.then((response) => response.json())
.then((json) => {
setUserList((prev) => [...prev, ...json]);
setCount((cnt) => {
if(cnt - 1 === 0){
setIsFetched(true);
}
return cnt - 1;
});
});
}, []);
useEffect(() => {
if (!isFetched) {
callApiPending();
}
}, [isFetched, userList, callApiPending]);
return <div>Executing....</div>;
}
You ran fetch if usersList changes. Even if userList content is the same as previous content, javascript interpret as it changed. Try this one.
[1,2,3] == [1,2,3]
may return false. You can use a flag which is used to check whether or not to get data instead of using array.
I am trying to set the state of a variable "workspace", but when I console log the data I get an infinite loop. I am calling the axios "get" function inside of useEffect(), and console logging outside of this loop, so I don't know what is triggering all the re-renders. I have not found an answer to my specific problem in this question. Here's my code:
function WorkspaceDynamic({ match }) {
const [proposals, setProposals] = useState([{}]);
useEffect(() => {
getItems();
});
const getItems = async () => {
const proposalsList = await axios.get(
"http://localhost:5000/api/proposals"
);
setProposals(proposalsList.data);
};
const [workspace, setWorkspace] = useState({});
function findWorkspace() {
proposals.map((workspace) => {
if (workspace._id === match.params.id) {
setWorkspace(workspace);
}
});
}
Does anyone see what might be causing the re-render? Thanks!
The effect hook runs every render cycle, and one without a dependency array will execute its callback every render cycle. If the effect callback updates state, i.e. proposals, then another render cycle is enqueued, thus creating render looping.
If you want to only run effect once when the component mounts then use an empty dependency array.
useEffect(() => {
getItems();
}, []);
If you want it to only run at certain time, like if the match param updates, then include a dependency in the array.
useEffect(() => {
getItems();
}, [match]);
Your use of useEffect is not correct. If you do not include a dependency array, it gets called every time the component renders. As a result your useEffect is called which causes setProposals then it again causes useEffect to run and so on
try this
useEffect(() => {
getItems();
} , []); // an empty array means it will be called once only
I think it's the following: useEffect should have a second param [] to make sure it's executed only once. that is:
useEffect(() => {
getItems();
}, []);
otherwise setProposal will modify the state which will trigger a re-render, which will call useEffect, which will make the async call, which will setProposal, ...
I have this component, that needs to fetch data, set it to state and then pass it to the children.
Some of the data also needs to be set in context.
My problem is that using useEffect, once called the API, it will re-render for each setvalue() function I need to execute.
I have tried passing to useEffect an empty [] array, still getting the same number of re-renders, due to the fact that the state is changing.
At the moment the array is containg the set...functions to prevent eslint to throw warnings.
Is there a better way to avoid this many re-renders ?
const Home = (props) => {
console.log("TCL: Home -> props", props);
const classes = useStyles();
const [value, setValue] = React.useState(0);
//CONTEXT
const { listSavedJobs, setListSavedJobs, setIsFullView} = useContext(HomeContext);
const {
setUserName,
setUserLastName,
setUserEmail,
setAvatarProfile,
} = useContext(UserContext);
// STATE
const [searchSettings, setSearchSettings] = useState([]);
const [oppData, setOppData] = useState([]);
const handleChange = (event, newValue) => {
setValue(newValue);
};
const handleChangeIndex = index => {
setValue(index);
};
//API CALLS
useEffect(() => {
const triggerAPI = async () => {
setIsFullView(false);
const oppResponse = await API.getOpportunity();
if(oppResponse){
setOppData(oppResponse.response);
}
const profileResponse = await API.getUserProfile();
if(profileResponse){
setUserName(profileResponse.response.first_name);
setUserLastName(profileResponse.response.last_name);
setUserEmail(profileResponse.response.emailId);
}
const profileExtData = await API.getUserProfileExt();
if(profileExtData){
setAvatarProfile(profileExtData.response.avatar);
setListSavedJobs(profileExtData.response.savedJobs);
setSearchSettings(profileExtData.response.preferredIndustry);
}
};
triggerAPI();
}, [
setOppData,
setUserName,
setUserLastName,
setUserEmail,
setAvatarProfile,
setListSavedJobs,
setIsFullView,
]);
...```
Pass just an empty array to second parameter of useEffect.
Note
React guarantees that setState function identity is stable and won’t
change on re-renders. This is why it’s safe to omit from the useEffect
or useCallback dependency list.
Source
Edit: Try this to avoid rerenders. Use with caution
Only Run on Mount and Unmount
You can pass the special value of empty array [] as a way of saying “only run on mount and unmount”. So if we changed our component above to call useEffect like this:
useEffect(() => {
console.log('mounted');
return () => console.log('unmounting...');
}, [])
Then it will print “mounted” after the initial render, remain silent throughout its life, and print “unmounting…” on its way out.
Prevent useEffect From Running Every Render
If you want your effects to run less often, you can provide a second argument – an array of values. Think of them as the dependencies for that effect. If one of the dependencies has changed since the last time, the effect will run again. (It will also still run after the initial render)
const [value, setValue] = useState('initial');
useEffect(() => {
// This effect uses the `value` variable,
// so it "depends on" `value`.
console.log(value);
}, [value])
For more clarification useEffect
If you are using React 18, this won't be a problem anymore as the new auto batching feature: https://reactjs.org/blog/2022/03/29/react-v18.html#new-feature-automatic-batching
If you are using an old version, can refer to this solution: https://statics.teams.cdn.office.net/evergreen-assets/safelinks/1/atp-safelinks.html