We Keep Coding

How to cleanup a async call in react component useEffect after unmount? [duplicate]

Problem
I am writing an application in React and was unable to avoid a super common pitfall, which is calling setState(...) after componentWillUnmount(...).
I looked very carefully at my code and tried to put some guarding clauses in place, but the problem persisted and I am still observing the warning.
Therefore, I've got two questions:
How do I figure out from the stack trace, which particular component and event handler or lifecycle hook is responsible for the rule violation?
Well, how to fix the problem itself, because my code was written with this pitfall in mind and is already trying to prevent it, but some underlying component's still generating the warning.
Browser console
Warning: Can't perform a React state update on an unmounted component.
This is a no-op, but it indicates a memory leak in your application.
To fix, cancel all subscriptions and asynchronous tasks in the componentWillUnmount
method.
in TextLayerInternal (created by Context.Consumer)
in TextLayer (created by PageInternal) index.js:1446
d/console[e]
index.js:1446
warningWithoutStack
react-dom.development.js:520
warnAboutUpdateOnUnmounted
react-dom.development.js:18238
scheduleWork
react-dom.development.js:19684
enqueueSetState
react-dom.development.js:12936
./node_modules/react/cjs/react.development.js/Component.prototype.setState
react.development.js:356
_callee$
TextLayer.js:97
tryCatch
runtime.js:63
invoke
runtime.js:282
defineIteratorMethods/</prototype[method]
runtime.js:116
asyncGeneratorStep
asyncToGenerator.js:3
_throw
asyncToGenerator.js:29
Code
Book.tsx
import { throttle } from 'lodash';
import * as React from 'react';
import { AutoWidthPdf } from '../shared/AutoWidthPdf';
import BookCommandPanel from '../shared/BookCommandPanel';
import BookTextPath from '../static/pdf/sde.pdf';
import './Book.css';
const DEFAULT_WIDTH = 140;
class Book extends React.Component {
setDivSizeThrottleable: () => void;
pdfWrapper: HTMLDivElement | null = null;
isComponentMounted: boolean = false;
state = {
hidden: true,
pdfWidth: DEFAULT_WIDTH,
};
constructor(props: any) {
super(props);
this.setDivSizeThrottleable = throttle(
() => {
if (this.isComponentMounted) {
this.setState({
pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
});
}
},
500,
);
}
componentDidMount = () => {
this.isComponentMounted = true;
this.setDivSizeThrottleable();
window.addEventListener("resize", this.setDivSizeThrottleable);
};
componentWillUnmount = () => {
this.isComponentMounted = false;
window.removeEventListener("resize", this.setDivSizeThrottleable);
};
render = () => (
<div className="Book">
{ this.state.hidden && <div className="Book__LoadNotification centered">Book is being loaded...</div> }
<div className={this.getPdfContentContainerClassName()}>
<BookCommandPanel
bookTextPath={BookTextPath}
/>
<div className="Book__PdfContent" ref={ref => this.pdfWrapper = ref}>
<AutoWidthPdf
file={BookTextPath}
width={this.state.pdfWidth}
onLoadSuccess={(_: any) => this.onDocumentComplete()}
/>
</div>
<BookCommandPanel
bookTextPath={BookTextPath}
/>
</div>
</div>
);
getPdfContentContainerClassName = () => this.state.hidden ? 'hidden' : '';
onDocumentComplete = () => {
try {
this.setState({ hidden: false });
this.setDivSizeThrottleable();
} catch (caughtError) {
console.warn({ caughtError });
}
};
}
export default Book;
AutoWidthPdf.tsx
import * as React from 'react';
import { Document, Page, pdfjs } from 'react-pdf';
pdfjs.GlobalWorkerOptions.workerSrc = `//cdnjs.cloudflare.com/ajax/libs/pdf.js/${pdfjs.version}/pdf.worker.js`;
interface IProps {
file: string;
width: number;
onLoadSuccess: (pdf: any) => void;
}
export class AutoWidthPdf extends React.Component<IProps> {
render = () => (
<Document
file={this.props.file}
onLoadSuccess={(_: any) => this.props.onLoadSuccess(_)}
>
<Page
pageNumber={1}
width={this.props.width}
/>
</Document>
);
}
Update 1: Cancel throttleable function (still no luck)
const DEFAULT_WIDTH = 140;
class Book extends React.Component {
setDivSizeThrottleable: ((() => void) & Cancelable) | undefined;
pdfWrapper: HTMLDivElement | null = null;
state = {
hidden: true,
pdfWidth: DEFAULT_WIDTH,
};
componentDidMount = () => {
this.setDivSizeThrottleable = throttle(
() => {
this.setState({
pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
});
},
500,
);
this.setDivSizeThrottleable();
window.addEventListener("resize", this.setDivSizeThrottleable);
};
componentWillUnmount = () => {
window.removeEventListener("resize", this.setDivSizeThrottleable!);
this.setDivSizeThrottleable!.cancel();
this.setDivSizeThrottleable = undefined;
};
render = () => (
<div className="Book">
{ this.state.hidden && <div className="Book__LoadNotification centered">Book is being loaded...</div> }
<div className={this.getPdfContentContainerClassName()}>
<BookCommandPanel
BookTextPath={BookTextPath}
/>
<div className="Book__PdfContent" ref={ref => this.pdfWrapper = ref}>
<AutoWidthPdf
file={BookTextPath}
width={this.state.pdfWidth}
onLoadSuccess={(_: any) => this.onDocumentComplete()}
/>
</div>
<BookCommandPanel
BookTextPath={BookTextPath}
/>
</div>
</div>
);
getPdfContentContainerClassName = () => this.state.hidden ? 'hidden' : '';
onDocumentComplete = () => {
try {
this.setState({ hidden: false });
this.setDivSizeThrottleable!();
} catch (caughtError) {
console.warn({ caughtError });
}
};
}
export default Book;

Here is a React Hooks specific solution for
Error
Warning: Can't perform a React state update on an unmounted component.
Solution
You can declare let isMounted = true inside useEffect, which will be changed in the cleanup callback, as soon as the component is unmounted. Before state updates, you now check this variable conditionally:
useEffect(() => {
let isMounted = true; // note mutable flag
someAsyncOperation().then(data => {
if (isMounted) setState(data); // add conditional check
})
return () => { isMounted = false }; // cleanup toggles value, if unmounted
}, []); // adjust dependencies to your needs
const Parent = () => {
const [mounted, setMounted] = useState(true);
return (
<div>
Parent:
<button onClick={() => setMounted(!mounted)}>
{mounted ? "Unmount" : "Mount"} Child
</button>
{mounted && <Child />}
<p>
Unmount Child, while it is still loading. It won't set state later on,
so no error is triggered.
</p>
</div>
);
};
const Child = () => {
const [state, setState] = useState("loading (4 sec)...");
useEffect(() => {
let isMounted = true;
fetchData();
return () => {
isMounted = false;
};
// simulate some Web API fetching
function fetchData() {
setTimeout(() => {
// drop "if (isMounted)" to trigger error again
// (take IDE, doesn't work with stack snippet)
if (isMounted) setState("data fetched")
else console.log("aborted setState on unmounted component")
}, 4000);
}
}, []);
return <div>Child: {state}</div>;
};
ReactDOM.render(<Parent />, document.getElementById("root"));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.0/umd/react.production.min.js" integrity="sha256-32Gmw5rBDXyMjg/73FgpukoTZdMrxuYW7tj8adbN8z4=" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.0/umd/react-dom.production.min.js" integrity="sha256-bjQ42ac3EN0GqK40pC9gGi/YixvKyZ24qMP/9HiGW7w=" crossorigin="anonymous"></script>
<div id="root"></div>
<script>var { useReducer, useEffect, useState, useRef } = React</script>
Extension: Custom useAsync Hook
We can encapsulate all the boilerplate into a custom Hook, that automatically aborts async functions in case the component unmounts or dependency values have changed before:
function useAsync(asyncFn, onSuccess) {
useEffect(() => {
let isActive = true;
asyncFn().then(data => {
if (isActive) onSuccess(data);
});
return () => { isActive = false };
}, [asyncFn, onSuccess]);
}
// custom Hook for automatic abortion on unmount or dependency change
// You might add onFailure for promise errors as well.
function useAsync(asyncFn, onSuccess) {
useEffect(() => {
let isActive = true;
asyncFn().then(data => {
if (isActive) onSuccess(data)
else console.log("aborted setState on unmounted component")
});
return () => {
isActive = false;
};
}, [asyncFn, onSuccess]);
}
const Child = () => {
const [state, setState] = useState("loading (4 sec)...");
useAsync(simulateFetchData, setState);
return <div>Child: {state}</div>;
};
const Parent = () => {
const [mounted, setMounted] = useState(true);
return (
<div>
Parent:
<button onClick={() => setMounted(!mounted)}>
{mounted ? "Unmount" : "Mount"} Child
</button>
{mounted && <Child />}
<p>
Unmount Child, while it is still loading. It won't set state later on,
so no error is triggered.
</p>
</div>
);
};
const simulateFetchData = () => new Promise(
resolve => setTimeout(() => resolve("data fetched"), 4000));
ReactDOM.render(<Parent />, document.getElementById("root"));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.0/umd/react.production.min.js" integrity="sha256-32Gmw5rBDXyMjg/73FgpukoTZdMrxuYW7tj8adbN8z4=" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.0/umd/react-dom.production.min.js" integrity="sha256-bjQ42ac3EN0GqK40pC9gGi/YixvKyZ24qMP/9HiGW7w=" crossorigin="anonymous"></script>
<div id="root"></div>
<script>var { useReducer, useEffect, useState, useRef } = React</script>
More on effect cleanups: Overreacted: A Complete Guide to useEffect

To remove - Can't perform a React state update on an unmounted component warning, use componentDidMount method under a condition and make false that condition on componentWillUnmount method. For example : -
class Home extends Component {
_isMounted = false;
constructor(props) {
super(props);
this.state = {
news: [],
};
}
componentDidMount() {
this._isMounted = true;
ajaxVar
.get('https://domain')
.then(result => {
if (this._isMounted) {
this.setState({
news: result.data.hits,
});
}
});
}
componentWillUnmount() {
this._isMounted = false;
}
render() {
...
}
}

If above solutions dont work, try this and it works for me:
componentWillUnmount() {
// fix Warning: Can't perform a React state update on an unmounted component
this.setState = (state,callback)=>{
return;
};
}

There is a hook that's fairly common called useIsMounted that solves this problem (for functional components)...
import { useRef, useEffect } from 'react';
export function useIsMounted() {
const isMounted = useRef(false);
useEffect(() => {
isMounted.current = true;
return () => isMounted.current = false;
}, []);
return isMounted;
}
then in your functional component
function Book() {
const isMounted = useIsMounted();
...
useEffect(() => {
asyncOperation().then(data => {
if (isMounted.current) { setState(data); }
})
});
...
}

Checking if a component is mounted is actually an anti pattern as per React documentation. The solution to the setState warning is rather to leverage on the use of an AbortController:
useEffect(() => {
const abortController = new AbortController() // creating an AbortController
fetch(url, { signal: abortController.signal }) // passing the signal to the query
.then(data => {
setState(data) // if everything went well, set the state
})
.catch(error => {
if (error.name === 'AbortError') return // if the query has been aborted, do nothing
throw error
})
return () => {
abortController.abort() // stop the query by aborting on the AbortController on unmount
}
}, [])
For asynchronous operations that aren't based on the Fetch API, there still should be a way to cancel these asynchronous operations, and you should rather leverage these than just checking if a component is mounted. If you are building your own API, you can implement the AbortController API in it to handle it.
For more context, the check if a component is mounted is an anti pattern as React is checking internally if the component is mounted to display that warning. Doing the same check again is just a way to hide the warning, and there are some easier ways to hide them than adding this piece of code on a big part of a codebase.
Source: https://medium.com/doctolib/react-stop-checking-if-your-component-is-mounted-3bb2568a4934

I had this warning possibly because of calling setState from an effect hook (This is discussed in these 3 issues linked together).
Anyway, upgrading the react version removed the warning.

React already removed this warning
but here is a better solution (not just workaround)
useEffect(() => {
const abortController = new AbortController() // creating an AbortController
fetch(url, { signal: abortController.signal }) // passing the signal to the query
.then(data => {
setState(data) // if everything went well, set the state
})
.catch(error => {
if (error.name === 'AbortError') return // if the query has been aborted, do nothing
throw error
})
return () => {
abortController.abort()
}
}, [])

The solution from #ford04 didn't worked to me and specially if you need to use the isMounted in multiple places (multiple useEffect for instance), it's recommended to useRef, as bellow:
Essential packages
"dependencies":
{
"react": "17.0.1",
}
"devDependencies": {
"typescript": "4.1.5",
}
My Hook Component
export const SubscriptionsView: React.FC = () => {
const [data, setData] = useState<Subscription[]>();
const isMounted = React.useRef(true);
React.useEffect(() => {
if (isMounted.current) {
// fetch data
// setData (fetch result)
return () => {
isMounted.current = false;
};
}
}
});

try changing setDivSizeThrottleable to
this.setDivSizeThrottleable = throttle(
() => {
if (this.isComponentMounted) {
this.setState({
pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
});
}
},
500,
{ leading: false, trailing: true }
);

I know that you're not using history, but in my case I was using the useHistory hook from React Router DOM, which unmounts the component before the state is persisted in my React Context Provider.
To fix this problem I have used the hook withRouter nesting the component, in my case export default withRouter(Login), and inside the component const Login = props => { ...; props.history.push("/dashboard"); .... I have also removed the other props.history.push from the component, e.g, if(authorization.token) return props.history.push('/dashboard') because this causes a loop, because the authorization state.
An alternative to push a new item to history.

Add a ref to a jsx component and then check it exist
function Book() {
const ref = useRef();
useEffect(() => {
asyncOperation().then(data => {
if (ref.current) setState(data);
})
});
return <div ref={ref}>content</div>
}

I had a similar issue thanks #ford04 helped me out.
However, another error occurred.
NB. I am using ReactJS hooks
ndex.js:1 Warning: Cannot update during an existing state transition (such as within `render`). Render methods should be a pure function of props and state.
What causes the error?
import {useHistory} from 'react-router-dom'
const History = useHistory()
if (true) {
history.push('/new-route');
}
return (
<>
<render component />
</>
)
This could not work because despite you are redirecting to new page all state and props are being manipulated on the dom or simply rendering to the previous page did not stop.
What solution I found
import {Redirect} from 'react-router-dom'
if (true) {
return <redirect to="/new-route" />
}
return (
<>
<render component />
</>
)

If you are fetching data from axios and the error still occurs, just wrap the setter inside the condition
let isRendered = useRef(false);
useEffect(() => {
isRendered = true;
axios
.get("/sample/api")
.then(res => {
if (isRendered) {
setState(res.data);
}
return null;
})
.catch(err => console.log(err));
return () => {
isRendered = false;
};
}, []);

I have 2 solutions for this error:
return:
If you are used hook and useEffect, So put a return end of useEffect.
useEffect(() => {
window.addEventListener('mousemove', logMouseMove)
return () => {
window.removeEventListener('mousemove', logMouseMove)
}
}, [])
componentWillUnmount:
If you are used componentDidMount, So put componentWillUnmount next to it.
componentDidMount() {
window.addEventListener('mousemove', this.logMouseMove)
}
componentWillUnmount() {
window.removeEventListener('mousemove', this.logMouseMove)
}

The isMounted approach is an anti-pattern in most cases because it doesn't actually clean up/cancel anything, it just avoids changing state on unmounted components, but does nothing with pending asynchronous tasks. The React team recently removed the leak warning because users keep creating a lot of anti-patterns to hide the warning rather than fix its cause.
But writing cancellable code in plain JS can be really tricky. To fix this I made my own lib useAsyncEffect2 with custom hooks, built on top of a cancellable promise (c-promise2) for executing cancellable async code to reach its graceful cancellation. All async stages (promises), including deep ones, are cancellable. This means that the request here will be automatically aborted if its parent context is canceled. Of course, any other asynchronous operation can be used instead of a request.
useAsyncEffect Demo with plain useState usage (Live Demo):
import React, { useState } from "react";
import { useAsyncEffect } from "use-async-effect2";
import cpAxios from "cp-axios";
function TestComponent({url}) {
const [text, setText] = useState("");
const cancel = useAsyncEffect(
function* () {
setText("fetching...");
const json = (yield cpAxios(url)).data;
setText(`Success: ${JSON.stringify(json)}`);
},
[url]
);
return (
<div>
<div>{text}</div>
<button onClick={cancel}>
Cancel request
</button>
</div>
);
}
useAsyncEffect Demo with internal states usage (Live Demo):
import React from "react";
import { useAsyncEffect } from "use-async-effect2";
import cpAxios from "cp-axios";
function TestComponent({ url, timeout }) {
const [cancel, done, result, err] = useAsyncEffect(
function* () {
return (yield cpAxios(url).timeout(timeout)).data;
},
{ states: true, deps: [url] }
);
return (
<div>
{done ? (err ? err.toString() : JSON.stringify(result)) : "loading..."}
<button onClick={cancel} disabled={done}>
Cancel async effect (abort request)
</button>
</div>
);
}
Class component using decorators (Live demo)
import React, { Component } from "react";
import { ReactComponent } from "c-promise2";
import cpAxios from "cp-axios";
#ReactComponent
class TestComponent extends Component {
state = {
text: ""
};
*componentDidMount(scope) {
const { url, timeout } = this.props;
const response = yield cpAxios(url).timeout(timeout);
this.setState({ text: JSON.stringify(response.data, null, 2) });
}
render() {
return (<div>{this.state.text}</div>);
}
}
export default TestComponent;
More other examples:
Axios request with errors handling
Fetch weather by coords
Live search
Pause & Resume
Progress capturing

Edit: I just realized the warning is referencing a component called TextLayerInternal. That's likely where your bug is. The rest of this is still relevant, but it might not fix your problem.
1) Getting the instance of a component for this warning is tough. It looks like there is some discussion to improve this in React but there currently is no easy way to do it. The reason it hasn't been built yet, I suspect, is likely because components are expected to be written in such a way that setState after unmount isn't possible no matter what the state of the component is. The problem, as far as the React team is concerned, is always in the Component code and not the Component instance, which is why you get the Component Type name.
That answer might be unsatisfactory, but I think I can fix your problem.
2) Lodashes throttled function has a cancel method. Call cancel in componentWillUnmount and ditch the isComponentMounted. Canceling is more "idiomatically" React than introducing a new property.

UPDATE DO NOT USE MY ORIGINAL ANSWER AS IT DOES NOT WORK
This answer was based on the use of cancelable promises and a note in makecancelable which I migrated to use hooks. However, it appears it does not cancel a chain of async/await and even cancelable-promise does not support canceling of a chain of awaits
Doing a bit more research on this, it appears that some internal Google reasons prevented cancelable promises from coming into the standard.
Further more, there was some promise with Bluebird which introduces cancelable promises, but it does not work in Expo or at least I haven't seen an example of it working in Expo.
The accepted answer is the best. Since I use TypeScript I had adapted the code with a few modifications (I explicitly set the dependencies since the accepted answer's implicit dependencies appear to give a re-render loop on my app, added and use async/await rather than promise chain, pass a ref to the mounted object so that an async/await chain can be canceled earlier if needed)
/**
* This starts an async function and executes another function that performs
* React state changes if the component is still mounted after the async
* operation completes
* #template T
* #param {(mountedRef: React.MutableRefObject<boolean>) => Promise<T>} asyncFunction async function,
* it has a copy of the mounted ref so an await chain can be canceled earlier.
* #param {(asyncResult: T) => void} onSuccess this gets executed after async
* function is resolved and the component is still mounted
* #param {import("react").DependencyList} deps
*/
export function useAsyncSetEffect(asyncFunction, onSuccess, deps) {
const mountedRef = useRef(false);
useEffect(() => {
mountedRef.current = true;
(async () => {
const x = await asyncFunction(mountedRef);
if (mountedRef.current) {
onSuccess(x);
}
})();
return () => {
mountedRef.current = false;
};
}, deps);
}
Original answer
Since I have many different operations that are async, I use the cancelable-promise package to resolve this issue with minimal code changes.
Previous code:
useEffect(() =>
(async () => {
const bar = await fooAsync();
setSomeState(bar);
})(),
[]
);
New code:
import { cancelable } from "cancelable-promise";
...
useEffect(
() => {
const cancelablePromise = cancelable(async () => {
const bar = await fooAsync();
setSomeState(bar);
})
return () => cancelablePromise.cancel();
},
[]
);
You can alsowrpte it in a custom utility function like this
/**
* This wraps an async function in a cancelable promise
* #param {() => PromiseLike<void>} asyncFunction
* #param {React.DependencyList} deps
*/
export function useCancelableEffect(asyncFunction, deps) {
useEffect(() => {
const cancelablePromise = cancelable(asyncFunction());
return () => cancelablePromise.cancel();
}, deps);
}

In my case of a login-like screen, the fetch was done in a onClick handler of a parent component, who passed that handler down to the child, whom placed .catch and .finally on it.
In the .then case a redirect (and hence unmount) would happen as normal operation, and only in cases of fetch error would the child stay mounted on-screen.
My solution was moving the setState and all other code from the .finally to the .catch since the child is guaranteed to be mounted in the .catch case. And in the .then case nothing needed doing because of the guaranteed unmount.

Based on #ford04 answer, here is the same encapsulated in a method :
import React, { FC, useState, useEffect, DependencyList } from 'react';
export function useEffectAsync( effectAsyncFun : ( isMounted: () => boolean ) => unknown, deps?: DependencyList ) {
useEffect( () => {
let isMounted = true;
const _unused = effectAsyncFun( () => isMounted );
return () => { isMounted = false; };
}, deps );
}
Usage:
const MyComponent : FC<{}> = (props) => {
const [ asyncProp , setAsyncProp ] = useState( '' ) ;
useEffectAsync( async ( isMounted ) =>
{
const someAsyncProp = await ... ;
if ( isMounted() )
setAsyncProp( someAsyncProp ) ;
});
return <div> ... ;
} ;

Depending on how you open your webpage, you may not be causing a mounting. Such as using a <Link/> back to a page that was already mounted in the virtual DOM, so requiring data from a componentDidMount lifecycle is caught.

Here is a simple solution for this. This warning is due to when we do some fetch request while that request is in the background (because some requests take some time.)and we navigate back from that screen then they react cannot update the state. here is the example code for this. write this line before every state Update.
if(!isScreenMounted.current) return;
Here is the Complete Code
import React , {useRef} from 'react'
import { Text,StatusBar,SafeAreaView,ScrollView, StyleSheet } from 'react-native'
import BASEURL from '../constants/BaseURL';
const SearchScreen = () => {
const isScreenMounted = useRef(true)
useEffect(() => {
return () => isScreenMounted.current = false
},[])
const ConvertFileSubmit = () => {
if(!isScreenMounted.current) return;
setUpLoading(true)
var formdata = new FormData();
var file = {
uri: `file://${route.params.selectedfiles[0].uri}`,
type:`${route.params.selectedfiles[0].minetype}`,
name:`${route.params.selectedfiles[0].displayname}`,
};
formdata.append("file",file);
fetch(`${BASEURL}/UploadFile`, {
method: 'POST',
body: formdata,
redirect: 'manual'
}).then(response => response.json())
.then(result => {
if(!isScreenMounted.current) return;
setUpLoading(false)
}).catch(error => {
console.log('error', error)
});
}
return(
<>
<StatusBar barStyle="dark-content" />
<SafeAreaView>
<ScrollView
contentInsetAdjustmentBehavior="automatic"
style={styles.scrollView}>
<Text>Search Screen</Text>
</ScrollView>
</SafeAreaView>
</>
)
}
export default SearchScreen;
const styles = StyleSheet.create({
scrollView: {
backgroundColor:"red",
},
container:{
flex:1,
justifyContent:"center",
alignItems:"center"
}
})

I solved this problem by providing all the params that are used in the useEffect hook
The code reported the bug:
useEffect(() => {
getDistrict({
geonameid: countryId,
subdistrict: level,
}).then((res) => {
......
});
}, [countryId]);
The code after fix:
useEffect(() => {
getDistrict({
geonameid: countryId,
subdistrict: level,
}).then((res) => {
......
});
}, [countryId,level]);
Can see that , problems solved after I provided all the params(including the level param) that supposed to pass through.

I had a similar problem and solved it :
I was automatically making the user logged-in by dispatching an action on redux
( placing authentication token on redux state )
and then I was trying to show a message with this.setState({succ_message: "...")
in my component.
Component was looking empty with the same error on console : "unmounted component".."memory leak" etc.
After I read Walter's answer up in this thread
I've noticed that in the Routing table of my application ,
my component's route wasn't valid if user is logged-in :
{!this.props.user.token &&
<div>
<Route path="/register/:type" exact component={MyComp} />
</div>
}
I made the Route visible whether the token exists or not.

In my case the issue was that the parent component was hidding the child because of a condition change in the child component.
So what I did was to change the condition so the child component was always shown.
What was happening:
const ParentComponent:FC = () => {
...
if (someCondition) {
return null;
}
return (
<>
Some cool text here
<ChildModalComponent message="this is a cool modal" />
</>
)
}
const ChildModalComponent: FC = () => {
...
const handleSubmit = () => {
setSomeCondition(true);
}
}
So after clicking submit the modal was automatically hidden becasue of the parent condition (someCondition).
How did I fix it?
I changed the place where the someCondition was checked in the Parent component, so the child component was always shown:
const ParentComponent:FC = () => {
...
return (
<>
{!someCondition && <>Some cool text here</>
<ChildModalComponent message="this is a cool modal" />
</>
)
}

I faced same warning, not it is fixed. To fix the issue, I removed the useRef() variable check in useEffect()
Earlier, the code was
const varRef = useRef();
useEffect(() => {
if (!varRef.current)
{
}
}, []);
Now, the code is
const varRef = useRef();
useEffect(() => {
//if (!varRef.current)
{
}
}, [])
Hope, it helps...

Inspired by the accepted answer by #ford04 I had even better approach dealing with it, instead of using useEffect inside useAsync create a new function that returns a callback for componentWillUnmount :
function asyncRequest(asyncRequest, onSuccess, onError, onComplete) {
let isMounted=true
asyncRequest().then((data => isMounted ? onSuccess(data):null)).catch(onError).finally(onComplete)
return () => {isMounted=false}
}
...
useEffect(()=>{
return asyncRequest(()=>someAsyncTask(arg), response=> {
setSomeState(response)
},onError, onComplete)
},[])

const handleClick = async (item: NavheadersType, index: number) => {
const newNavHeaders = [...navheaders];
if (item.url) {
await router.push(item.url); =>>>> line causing error (causing route to happen)
// router.push(item.url); =>>> coreect line
newNavHeaders.forEach((item) => (item.active = false));
newNavHeaders[index].active = true;
setnavheaders([...newNavHeaders]);
}
};

The simplest and most compact solution (with an explanation) is seen below as a one-liner solution.
useEffect(() => { return () => {}; }, []);
The useEffect() example above returns a callback function triggers React to finish its unmount portion of its life-cycle prior to updating state.
That very simplistic solution is all that is needed. In addition, it also works unlike the fictional syntax provided by #ford04 and #sfletche . By the way, the below code snippet from #ford04 is purely imaginary syntax (#sfletche , #vinod , #guneetgstar , and #Drew Cordano used the very same imaginary syntax).
data => {       <--- Fictional/Imaginary Syntax
someAsyncOperation().then(data => {
if (isMounted) setState(data); // add conditional check
})
All of my linters and all the linters of my entire team will not accept it and they report Uncaught SyntaxError: unexpected token: '=>'. I am surprised that no one caught the imaginary syntax. Would anyone who has participated in this question-thread, particularly among the up-voters, explain to me how they got the solutions to work for them?

Inspired by #ford04 answer I use this hook, which also takes callbacks for success, errors, finally and an abortFn:
export const useAsync = (
asyncFn,
onSuccess = false,
onError = false,
onFinally = false,
abortFn = false
) => {
useEffect(() => {
let isMounted = true;
const run = async () => {
try{
let data = await asyncFn()
if (isMounted && onSuccess) onSuccess(data)
} catch(error) {
if (isMounted && onError) onSuccess(error)
} finally {
if (isMounted && onFinally) onFinally()
}
}
run()
return () => {
if(abortFn) abortFn()
isMounted = false
};
}, [asyncFn, onSuccess])
}
If the asyncFn is doing some kind of fetch from back-end it often makes sense to abort it when the component is unmounted (not always though, sometimes if ie. you're loading some data into a store you might as well just want to finish it even if component is unmounted)

conditional rendering with toast and usestate does not work with react

I have my state and I want to display the component if the value is true but in the console I receive the error message Cannot update during an existing state transition (such as within render). Render methods should be a pure function of props and state my code
import React, { useState} from "react";
import { useToasts } from "react-toast-notifications";
const Index = () => {
const [test, setTest]= useState(true);
const { addToast } = useToasts();
function RenderToast() {
return (
<div>
{ addToast('message') }
</div>
)}
return (
<div>
{test && <RenderToast /> }
</div>
)
}

You cannot set state during a render. And I'm guessing that addToast internally sets some state.
And looking at the docs for that library, you don't explicitly render the toasts. You just call addToast and then the <ToastProvider/> farther up in the tree shows them.
So to make this simple example works where a toast is shown on mount, you should use an effect to add the toast after the first render, and make sure your component is wrapped by <ToastProvider>
const Index = () => {
const { addToast } = useToasts();
useEffect(() => {
addToast('message')
}, [])
return <>Some Content here</>
}
// Example app that includes the toast provider
const MyApp = () => {
<ToastProvider>
<Index />
</ToastProvider>
}
how i can display the toast based on a variable for exemple display toast after receive error on backend?
You simply call addToast where you are handling your server communication.
For example:
const Index = () => {
const { addToast } = useToasts();
useEffect(() => {
fetchDataFromApi()
.then(data => ...)
.catch(error => addToast(`error: ${error}`))
}, [])
//...
}

Issues triggering Modal to show inside useEffect hook [duplicate]

I get this error:
Can't perform a React state update on an unmounted component. This is
a no-op, but it indicates a memory leak in your application. To fix,
cancel all subscriptions and asynchronous tasks in a useEffect cleanup
function.
when fetching of data is started and component was unmounted, but function is trying to update state of unmounted component.
What is the best way to solve this?
CodePen example.
default function Test() {
const [notSeenAmount, setNotSeenAmount] = useState(false)
useEffect(() => {
let timer = setInterval(updateNotSeenAmount, 2000)
return () => clearInterval(timer)
}, [])
async function updateNotSeenAmount() {
let data // here i fetch data
setNotSeenAmount(data) // here is problem. If component was unmounted, i get error.
}
async function anotherFunction() {
updateNotSeenAmount() //it can trigger update too
}
return <button onClick={updateNotSeenAmount}>Push me</button> //update can be triggered manually
}

The easiest solution is to use a local variable that keeps track of whether the component is mounted or not. This is a common pattern with the class based approach. Here is an example that implement it with hooks:
function Example() {
const [text, setText] = React.useState("waiting...");
React.useEffect(() => {
let isCancelled = false;
simulateSlowNetworkRequest().then(() => {
if (!isCancelled) {
setText("done!");
}
});
return () => {
isCancelled = true;
};
}, []);
return <h2>{text}</h2>;
}
Here is an alternative with useRef (see below). Note that with a list of dependencies this solution won't work. The value of the ref will stay true after the first render. In that case the first solution is more appropriate.
function Example() {
const isCancelled = React.useRef(false);
const [text, setText] = React.useState("waiting...");
React.useEffect(() => {
fetch();
return () => {
isCancelled.current = true;
};
}, []);
function fetch() {
simulateSlowNetworkRequest().then(() => {
if (!isCancelled.current) {
setText("done!");
}
});
}
return <h2>{text}</h2>;
}
You can find more information about this pattern inside this article. Here is an issue inside the React project on GitHub that showcase this solution.

If you are fetching data from axios(using hooks) and the error still occurs, just wrap the setter inside the condition
let isRendered = useRef(false);
useEffect(() => {
isRendered = true;
axios
.get("/sample/api")
.then(res => {
if (isRendered) {
setState(res.data);
}
return null;
})
.catch(err => console.log(err));
return () => {
isRendered = false;
};
}, []);

TL;DR
Here is a CodeSandBox example
The other answers work of course, I just wanted to share a solution I came up with.
I built this hook that works just like React's useState, but will only setState if the component is mounted. I find it more elegant because you don't have to mess arround with an isMounted variable in your component !
Installation :
npm install use-state-if-mounted
Usage :
const [count, setCount] = useStateIfMounted(0);
You can find more advanced documentation on the npm page of the hook.

Here is a simple solution for this. This warning is due to when we do some fetch request while that request is in the background (because some requests take some time.)and we navigate back from that screen then react cannot update the state. here is the example code for this. write this line before every state Update.
if(!isScreenMounted.current) return;
Here is Complete Example
import React , {useRef} from 'react'
import { Text,StatusBar,SafeAreaView,ScrollView, StyleSheet } from 'react-native'
import BASEURL from '../constants/BaseURL';
const SearchScreen = () => {
const isScreenMounted = useRef(true)
useEffect(() => {
return () => isScreenMounted.current = false
},[])
const ConvertFileSubmit = () => {
if(!isScreenMounted.current) return;
setUpLoading(true)
var formdata = new FormData();
var file = {
uri: `file://${route.params.selectedfiles[0].uri}`,
type:`${route.params.selectedfiles[0].minetype}`,
name:`${route.params.selectedfiles[0].displayname}`,
};
formdata.append("file",file);
fetch(`${BASEURL}/UploadFile`, {
method: 'POST',
body: formdata,
redirect: 'manual'
}).then(response => response.json())
.then(result => {
if(!isScreenMounted.current) return;
setUpLoading(false)
}).catch(error => {
console.log('error', error)
});
}
return(
<>
<StatusBar barStyle="dark-content" />
<SafeAreaView>
<ScrollView
contentInsetAdjustmentBehavior="automatic"
style={styles.scrollView}>
<Text>Search Screen</Text>
</ScrollView>
</SafeAreaView>
</>
)
}
export default SearchScreen;
const styles = StyleSheet.create({
scrollView: {
backgroundColor:"red",
},
container:{
flex:1,
justifyContent:"center",
alignItems:"center"
}
})

This answer is not related to the specific question but I got the same Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function. and as a React newcomer could not find a solution to it.
My problem was related to useState in an unmounted component.
I noticed that I was calling a set state function (setIsLoading) after the function that unmounted my component:
const Login = () => {
const [isLoading, setIsLoading] = useState(false);
const handleLogin = () => {
setIsLoading(true);
firebase.auth().then(
functionToUnMountLoginSection();
// the problem is here
setIsLoading(false);
)
}
}
The correct way is to call setIsLoading when the component is still mounted, before calling the function to unmount/process user login in my specific case:
firebase.auth().then(
setIsLoading(false);
functionToUnMountLoginSection();
)

You add the state related datas into the useEffect body for not rerunning them every rerendering process. This method will solve the problem.
useEffect(() => {
let timer = setInterval(updateNotSeenAmount, 2000)
return () => clearInterval(timer)
}, [notSeenAmount])
REF: Tip: Optimizing Performance by Skipping Effects

Custom Hook Solution (ReactJs/NextJs)
Create a new folder named 'shared' and add two folders named 'hooks', 'utils' in it. Add a new file called 'commonFunctions.js' inside utils folder and add the code snippet below.
export const promisify = (fn) => {
return new Promise((resolve, reject) => {
fn
.then(response => resolve(response))
.catch(error => reject(error));
});
};
Add a new file called 'fetch-hook.js' inside hooks folder and add the code snippet below.
import { useCallback, useEffect, useRef } from "react";
import { promisify } from "../utils/commonFunctions";
export const useFetch = () => {
const isUnmounted = useRef(false);
useEffect(() => {
isUnmounted.current = false;
return () => {
isUnmounted.current = true;
};
}, []);
const call = useCallback((fn, onSuccess, onError = null) => {
promisify(fn).then(response => {
console.group('useFetch Hook response', response);
if (!isUnmounted.current) {
console.log('updating state..');
onSuccess(response.data);
}
else
console.log('aborted state update!');
console.groupEnd();
}).catch(error => {
console.log("useFetch Hook error", error);
if (!isUnmounted.current)
if (onError)
onError(error);
});
}, []);
return { call }
};
Folder Structure
Our custom hook is now ready. We use it in our component like below
const OurComponent = (props) => {
//..
const [subscriptions, setSubscriptions] = useState<any>([]);
//..
const { call } = useFetch();
// example method, change with your own
const getSubscriptions = useCallback(async () => {
call(
payment.companySubscriptions(userId), // example api call, change with your own
(data) => setSubscriptions(data),
);
}, [userId]);
//..
const updateSubscriptions = useCallback(async () => {
setTimeout(async () => {
await getSubscriptions();
}, 5000);// 5 seconds delay
}, [getSubscriptions]);
//..
}
In our component, we call 'updateSubscriptions' method. It will trigger 'getSubscriptions' method in which we used our custom hook. If we try to navigate to a different page after calling updateSubscriptions method before 5 seconds over, our custom hook will abort state update and prevent that warning on the title of this question
Wanna see opposite?
Change 'getSubscriptions' method with the one below
const getSubscriptions = useCallback(async () => {
const response = await payment.companySubscriptions(userId);
setSubscriptions(response);
}, [userId]);
Now try to call 'updateSubscriptions' method and navigate to a different page before 5 seconds over

Try this custom hook:
import { useEffect, useRef } from 'react';
export const useIsMounted = () => {
const isMounted = useRef(false);
useEffect(() => {
isMounted.current = true;
return () => (isMounted.current = false);
}, []);
return isMounted;
};
function Example() {
const isMounted = useIsMounted();
const [text, setText] = useState();
const safeSetState = useCallback((callback, ...args) => {
if (isMounted.current) {
callback(...args);
}
}, []);
useEffect(() => {
safeSetState(setText, 'Hello')
});
}, []);
return <h2>{text}</h2>;
}

How to call a componentDidMount in the functional component [duplicate]

Instead of writing my components inside a class, I'd like to use the function syntax.
How do I override componentDidMount, componentWillMount inside function components?
Is it even possible?
const grid = (props) => {
console.log(props);
let {skuRules} = props;
const componentDidMount = () => {
if(!props.fetched) {
props.fetchRules();
}
console.log('mount it!');
};
return(
<Content title="Promotions" breadcrumbs={breadcrumbs} fetched={skuRules.fetched}>
<Box title="Sku Promotion">
<ActionButtons buttons={actionButtons} />
<SkuRuleGrid
data={skuRules.payload}
fetch={props.fetchSkuRules}
/>
</Box>
</Content>
)
}

Edit: With the introduction of Hooks it is possible to implement a lifecycle kind of behavior as well as the state in the functional Components. Currently
Hooks are a new feature proposal that lets you use state and other
React features without writing a class. They are released in React as a part of v16.8.0
useEffect hook can be used to replicate lifecycle behavior, and useState can be used to store state in a function component.
Basic syntax:
useEffect(callbackFunction, [dependentProps]) => cleanupFunction
You can implement your use case in hooks like
const grid = (props) => {
console.log(props);
let {skuRules} = props;
useEffect(() => {
if(!props.fetched) {
props.fetchRules();
}
console.log('mount it!');
}, []); // passing an empty array as second argument triggers the callback in useEffect only after the initial render thus replicating `componentDidMount` lifecycle behaviour
return(
<Content title="Promotions" breadcrumbs={breadcrumbs} fetched={skuRules.fetched}>
<Box title="Sku Promotion">
<ActionButtons buttons={actionButtons} />
<SkuRuleGrid
data={skuRules.payload}
fetch={props.fetchSkuRules}
/>
</Box>
</Content>
)
}
useEffect can also return a function that will be run when the component is unmounted. This can be used to unsubscribe to listeners, replicating the behavior of componentWillUnmount:
Eg: componentWillUnmount
useEffect(() => {
window.addEventListener('unhandledRejection', handler);
return () => {
window.removeEventListener('unhandledRejection', handler);
}
}, [])
To make useEffect conditional on specific events, you may provide it with an array of values to check for changes:
Eg: componentDidUpdate
componentDidUpdate(prevProps, prevState) {
const { counter } = this.props;
if (this.props.counter !== prevState.counter) {
// some action here
}
}
Hooks Equivalent
useEffect(() => {
// action here
}, [props.counter]); // checks for changes in the values in this array
If you include this array, make sure to include all values from the component scope that change over time (props, state), or you may end up referencing values from previous renders.
There are some subtleties to using useEffect; check out the API Here.
Before v16.7.0
The property of function components is that they don't have access to Reacts lifecycle functions or the this keyword. You need to extend the React.Component class if you want to use the lifecycle function.
class Grid extends React.Component {
constructor(props) {
super(props)
}
componentDidMount () {
if(!this.props.fetched) {
this.props.fetchRules();
}
console.log('mount it!');
}
render() {
return(
<Content title="Promotions" breadcrumbs={breadcrumbs} fetched={skuRules.fetched}>
<Box title="Sku Promotion">
<ActionButtons buttons={actionButtons} />
<SkuRuleGrid
data={skuRules.payload}
fetch={props.fetchSkuRules}
/>
</Box>
</Content>
)
}
}
Function components are useful when you only want to render your Component without the need of extra logic.

You can use react-pure-lifecycle to add lifecycle functions to functional components.
Example:
import React, { Component } from 'react';
import lifecycle from 'react-pure-lifecycle';
const methods = {
componentDidMount(props) {
console.log('I mounted! Here are my props: ', props);
}
};
const Channels = props => (
<h1>Hello</h1>
)
export default lifecycle(methods)(Channels);

You can make your own "lifecycle methods" using hooks for maximum nostalgia.
Utility functions:
import { useEffect, useRef } from "react";
export const useComponentDidMount = handler => {
return useEffect(() => handler(), []);
};
export const useComponentDidUpdate = (handler, deps) => {
const isInitialMount = useRef(true);
useEffect(() => {
if (isInitialMount.current) {
isInitialMount.current = false;
return;
}
return handler();
}, deps);
};
export const useComponentWillUnmount = handler => {
return useEffect(() => handler, []);
};
Usage:
import {
useComponentDidMount,
useComponentDidUpdate,
useComponentWillUnmount
} from "./utils";
export const MyComponent = ({ myProp }) => {
useComponentDidMount(() => {
console.log("Component did mount!");
});
useComponentDidUpdate(() => {
console.log("Component did update!");
});
useComponentDidUpdate(() => {
console.log("myProp did update!");
}, [myProp]);
useComponentWillUnmount(() => {
console.log("Component will unmount!");
});
return <div>Hello world</div>;
};

Solution One:
You can use new react HOOKS API. Currently in React v16.8.0
Hooks let you use more of React’s features without classes.
Hooks provide a more direct API to the React concepts you already know: props, state, context, refs, and lifecycle.
Hooks solves all the problems addressed with Recompose.
A Note from the Author of recompose (acdlite, Oct 25 2018):
Hi! I created Recompose about three years ago. About a year after
that, I joined the React team. Today, we announced a proposal for
Hooks. Hooks solves all the problems I attempted to address with
Recompose three years ago, and more on top of that. I will be
discontinuing active maintenance of this package (excluding perhaps
bugfixes or patches for compatibility with future React releases), and
recommending that people use Hooks instead. Your existing code with
Recompose will still work, just don't expect any new features.
Solution Two:
If you are using react version that does not support hooks, no worries, use recompose(A React utility belt for function components and higher-order components.) instead. You can use recompose for attaching lifecycle hooks, state, handlers etc to a function component.
Here’s a render-less component that attaches lifecycle methods via the lifecycle HOC (from recompose).
// taken from https://gist.github.com/tsnieman/056af4bb9e87748c514d#file-auth-js-L33
function RenderlessComponent() {
return null;
}
export default lifecycle({
componentDidMount() {
const { checkIfAuthed } = this.props;
// Do they have an active session? ("Remember me")
checkIfAuthed();
},
componentWillReceiveProps(nextProps) {
const {
loadUser,
} = this.props;
// Various 'indicators'..
const becameAuthed = (!(this.props.auth) && nextProps.auth);
const isCurrentUser = (this.props.currentUser !== null);
if (becameAuthed) {
loadUser(nextProps.auth.uid);
}
const shouldSetCurrentUser = (!isCurrentUser && nextProps.auth);
if (shouldSetCurrentUser) {
const currentUser = nextProps.users[nextProps.auth.uid];
if (currentUser) {
this.props.setCurrentUser({
'id': nextProps.auth.uid,
...currentUser,
});
}
}
}
})(RenderlessComponent);

componentDidMount
useEffect(()=>{
// code here
})
componentWillMount
useEffect(()=>{
return ()=>{
//code here
}
})
componentDidUpdate
useEffect(()=>{
//code here
// when userName state change it will call
},[userName])

According to the documentation:
import React, { useState, useEffect } from 'react'
// Similar to componentDidMount and componentDidUpdate:
useEffect(() => {
});
see React documentation

Short and sweet answer
componentDidMount
useEffect(()=>{
// code here
})
componentWillUnmount
useEffect(()=>{
return ()=>{
//code here
}
})
componentDidUpdate
useEffect(()=>{
//code here
// when userName state change it will call
},[userName])

You can make use of create-react-class module.
Official documentation
Of course you must first install it
npm install create-react-class
Here is a working example
import React from "react";
import ReactDOM from "react-dom"
let createReactClass = require('create-react-class')
let Clock = createReactClass({
getInitialState:function(){
return {date:new Date()}
},
render:function(){
return (
<h1>{this.state.date.toLocaleTimeString()}</h1>
)
},
componentDidMount:function(){
this.timerId = setInterval(()=>this.setState({date:new Date()}),1000)
},
componentWillUnmount:function(){
clearInterval(this.timerId)
}
})
ReactDOM.render(
<Clock/>,
document.getElementById('root')
)

if you using react 16.8 you can use react Hooks...
React Hooks are functions that let you “hook into” React state and lifecycle features from function components...
docs

import React, { useState, useEffect } from "react";
const Counter = () => {
const [count, setCount] = useState(0);
const [count2, setCount2] = useState(0);
// componentDidMount
useEffect(() => {
console.log("The use effect ran");
}, []);
// // componentDidUpdate
useEffect(() => {
console.log("The use effect ran");
}, [count, count2]);
// componentWillUnmount
useEffect(() => {
console.log("The use effect ran");
return () => {
console.log("the return is being ran");
};
}, []);
useEffect(() => {
console.log(`The count has updated to ${count}`);
return () => {
console.log(`we are in the cleanup - the count is ${count}`);
};
}, [count]);
return (
<div>
<h6> Counter </h6>
<p> current count: {count} </p>
<button onClick={() => setCount(count + 1)}>increment the count</button>
<button onClick={() => setCount2(count2 + 1)}>increment count 2</button>
</div>
);
};
export default Counter;

Can't perform a React state update on an unmounted component

Problem
I am writing an application in React and was unable to avoid a super common pitfall, which is calling setState(...) after componentWillUnmount(...).
I looked very carefully at my code and tried to put some guarding clauses in place, but the problem persisted and I am still observing the warning.
Therefore, I've got two questions:
How do I figure out from the stack trace, which particular component and event handler or lifecycle hook is responsible for the rule violation?
Well, how to fix the problem itself, because my code was written with this pitfall in mind and is already trying to prevent it, but some underlying component's still generating the warning.
Browser console
Warning: Can't perform a React state update on an unmounted component.
This is a no-op, but it indicates a memory leak in your application.
To fix, cancel all subscriptions and asynchronous tasks in the componentWillUnmount
method.
in TextLayerInternal (created by Context.Consumer)
in TextLayer (created by PageInternal) index.js:1446
d/console[e]
index.js:1446
warningWithoutStack
react-dom.development.js:520
warnAboutUpdateOnUnmounted
react-dom.development.js:18238
scheduleWork
react-dom.development.js:19684
enqueueSetState
react-dom.development.js:12936
./node_modules/react/cjs/react.development.js/Component.prototype.setState
react.development.js:356
_callee$
TextLayer.js:97
tryCatch
runtime.js:63
invoke
runtime.js:282
defineIteratorMethods/</prototype[method]
runtime.js:116
asyncGeneratorStep
asyncToGenerator.js:3
_throw
asyncToGenerator.js:29
Code
Book.tsx
import { throttle } from 'lodash';
import * as React from 'react';
import { AutoWidthPdf } from '../shared/AutoWidthPdf';
import BookCommandPanel from '../shared/BookCommandPanel';
import BookTextPath from '../static/pdf/sde.pdf';
import './Book.css';
const DEFAULT_WIDTH = 140;
class Book extends React.Component {
setDivSizeThrottleable: () => void;
pdfWrapper: HTMLDivElement | null = null;
isComponentMounted: boolean = false;
state = {
hidden: true,
pdfWidth: DEFAULT_WIDTH,
};
constructor(props: any) {
super(props);
this.setDivSizeThrottleable = throttle(
() => {
if (this.isComponentMounted) {
this.setState({
pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
});
}
},
500,
);
}
componentDidMount = () => {
this.isComponentMounted = true;
this.setDivSizeThrottleable();
window.addEventListener("resize", this.setDivSizeThrottleable);
};
componentWillUnmount = () => {
this.isComponentMounted = false;
window.removeEventListener("resize", this.setDivSizeThrottleable);
};
render = () => (
<div className="Book">
{ this.state.hidden && <div className="Book__LoadNotification centered">Book is being loaded...</div> }
<div className={this.getPdfContentContainerClassName()}>
<BookCommandPanel
bookTextPath={BookTextPath}
/>
<div className="Book__PdfContent" ref={ref => this.pdfWrapper = ref}>
<AutoWidthPdf
file={BookTextPath}
width={this.state.pdfWidth}
onLoadSuccess={(_: any) => this.onDocumentComplete()}
/>
</div>
<BookCommandPanel
bookTextPath={BookTextPath}
/>
</div>
</div>
);
getPdfContentContainerClassName = () => this.state.hidden ? 'hidden' : '';
onDocumentComplete = () => {
try {
this.setState({ hidden: false });
this.setDivSizeThrottleable();
} catch (caughtError) {
console.warn({ caughtError });
}
};
}
export default Book;
AutoWidthPdf.tsx
import * as React from 'react';
import { Document, Page, pdfjs } from 'react-pdf';
pdfjs.GlobalWorkerOptions.workerSrc = `//cdnjs.cloudflare.com/ajax/libs/pdf.js/${pdfjs.version}/pdf.worker.js`;
interface IProps {
file: string;
width: number;
onLoadSuccess: (pdf: any) => void;
}
export class AutoWidthPdf extends React.Component<IProps> {
render = () => (
<Document
file={this.props.file}
onLoadSuccess={(_: any) => this.props.onLoadSuccess(_)}
>
<Page
pageNumber={1}
width={this.props.width}
/>
</Document>
);
}
Update 1: Cancel throttleable function (still no luck)
const DEFAULT_WIDTH = 140;
class Book extends React.Component {
setDivSizeThrottleable: ((() => void) & Cancelable) | undefined;
pdfWrapper: HTMLDivElement | null = null;
state = {
hidden: true,
pdfWidth: DEFAULT_WIDTH,
};
componentDidMount = () => {
this.setDivSizeThrottleable = throttle(
() => {
this.setState({
pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
});
},
500,
);
this.setDivSizeThrottleable();
window.addEventListener("resize", this.setDivSizeThrottleable);
};
componentWillUnmount = () => {
window.removeEventListener("resize", this.setDivSizeThrottleable!);
this.setDivSizeThrottleable!.cancel();
this.setDivSizeThrottleable = undefined;
};
render = () => (
<div className="Book">
{ this.state.hidden && <div className="Book__LoadNotification centered">Book is being loaded...</div> }
<div className={this.getPdfContentContainerClassName()}>
<BookCommandPanel
BookTextPath={BookTextPath}
/>
<div className="Book__PdfContent" ref={ref => this.pdfWrapper = ref}>
<AutoWidthPdf
file={BookTextPath}
width={this.state.pdfWidth}
onLoadSuccess={(_: any) => this.onDocumentComplete()}
/>
</div>
<BookCommandPanel
BookTextPath={BookTextPath}
/>
</div>
</div>
);
getPdfContentContainerClassName = () => this.state.hidden ? 'hidden' : '';
onDocumentComplete = () => {
try {
this.setState({ hidden: false });
this.setDivSizeThrottleable!();
} catch (caughtError) {
console.warn({ caughtError });
}
};
}
export default Book;

Here is a React Hooks specific solution for
Error
Warning: Can't perform a React state update on an unmounted component.
Solution
You can declare let isMounted = true inside useEffect, which will be changed in the cleanup callback, as soon as the component is unmounted. Before state updates, you now check this variable conditionally:
useEffect(() => {
let isMounted = true; // note mutable flag
someAsyncOperation().then(data => {
if (isMounted) setState(data); // add conditional check
})
return () => { isMounted = false }; // cleanup toggles value, if unmounted
}, []); // adjust dependencies to your needs
const Parent = () => {
const [mounted, setMounted] = useState(true);
return (
<div>
Parent:
<button onClick={() => setMounted(!mounted)}>
{mounted ? "Unmount" : "Mount"} Child
</button>
{mounted && <Child />}
<p>
Unmount Child, while it is still loading. It won't set state later on,
so no error is triggered.
</p>
</div>
);
};
const Child = () => {
const [state, setState] = useState("loading (4 sec)...");
useEffect(() => {
let isMounted = true;
fetchData();
return () => {
isMounted = false;
};
// simulate some Web API fetching
function fetchData() {
setTimeout(() => {
// drop "if (isMounted)" to trigger error again
// (take IDE, doesn't work with stack snippet)
if (isMounted) setState("data fetched")
else console.log("aborted setState on unmounted component")
}, 4000);
}
}, []);
return <div>Child: {state}</div>;
};
ReactDOM.render(<Parent />, document.getElementById("root"));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.0/umd/react.production.min.js" integrity="sha256-32Gmw5rBDXyMjg/73FgpukoTZdMrxuYW7tj8adbN8z4=" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.0/umd/react-dom.production.min.js" integrity="sha256-bjQ42ac3EN0GqK40pC9gGi/YixvKyZ24qMP/9HiGW7w=" crossorigin="anonymous"></script>
<div id="root"></div>
<script>var { useReducer, useEffect, useState, useRef } = React</script>
Extension: Custom useAsync Hook
We can encapsulate all the boilerplate into a custom Hook, that automatically aborts async functions in case the component unmounts or dependency values have changed before:
function useAsync(asyncFn, onSuccess) {
useEffect(() => {
let isActive = true;
asyncFn().then(data => {
if (isActive) onSuccess(data);
});
return () => { isActive = false };
}, [asyncFn, onSuccess]);
}
// custom Hook for automatic abortion on unmount or dependency change
// You might add onFailure for promise errors as well.
function useAsync(asyncFn, onSuccess) {
useEffect(() => {
let isActive = true;
asyncFn().then(data => {
if (isActive) onSuccess(data)
else console.log("aborted setState on unmounted component")
});
return () => {
isActive = false;
};
}, [asyncFn, onSuccess]);
}
const Child = () => {
const [state, setState] = useState("loading (4 sec)...");
useAsync(simulateFetchData, setState);
return <div>Child: {state}</div>;
};
const Parent = () => {
const [mounted, setMounted] = useState(true);
return (
<div>
Parent:
<button onClick={() => setMounted(!mounted)}>
{mounted ? "Unmount" : "Mount"} Child
</button>
{mounted && <Child />}
<p>
Unmount Child, while it is still loading. It won't set state later on,
so no error is triggered.
</p>
</div>
);
};
const simulateFetchData = () => new Promise(
resolve => setTimeout(() => resolve("data fetched"), 4000));
ReactDOM.render(<Parent />, document.getElementById("root"));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.0/umd/react.production.min.js" integrity="sha256-32Gmw5rBDXyMjg/73FgpukoTZdMrxuYW7tj8adbN8z4=" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.0/umd/react-dom.production.min.js" integrity="sha256-bjQ42ac3EN0GqK40pC9gGi/YixvKyZ24qMP/9HiGW7w=" crossorigin="anonymous"></script>
<div id="root"></div>
<script>var { useReducer, useEffect, useState, useRef } = React</script>
More on effect cleanups: Overreacted: A Complete Guide to useEffect

To remove - Can't perform a React state update on an unmounted component warning, use componentDidMount method under a condition and make false that condition on componentWillUnmount method. For example : -
class Home extends Component {
_isMounted = false;
constructor(props) {
super(props);
this.state = {
news: [],
};
}
componentDidMount() {
this._isMounted = true;
ajaxVar
.get('https://domain')
.then(result => {
if (this._isMounted) {
this.setState({
news: result.data.hits,
});
}
});
}
componentWillUnmount() {
this._isMounted = false;
}
render() {
...
}
}

If above solutions dont work, try this and it works for me:
componentWillUnmount() {
// fix Warning: Can't perform a React state update on an unmounted component
this.setState = (state,callback)=>{
return;
};
}

There is a hook that's fairly common called useIsMounted that solves this problem (for functional components)...
import { useRef, useEffect } from 'react';
export function useIsMounted() {
const isMounted = useRef(false);
useEffect(() => {
isMounted.current = true;
return () => isMounted.current = false;
}, []);
return isMounted;
}
then in your functional component
function Book() {
const isMounted = useIsMounted();
...
useEffect(() => {
asyncOperation().then(data => {
if (isMounted.current) { setState(data); }
})
});
...
}

Checking if a component is mounted is actually an anti pattern as per React documentation. The solution to the setState warning is rather to leverage on the use of an AbortController:
useEffect(() => {
const abortController = new AbortController() // creating an AbortController
fetch(url, { signal: abortController.signal }) // passing the signal to the query
.then(data => {
setState(data) // if everything went well, set the state
})
.catch(error => {
if (error.name === 'AbortError') return // if the query has been aborted, do nothing
throw error
})
return () => {
abortController.abort() // stop the query by aborting on the AbortController on unmount
}
}, [])
For asynchronous operations that aren't based on the Fetch API, there still should be a way to cancel these asynchronous operations, and you should rather leverage these than just checking if a component is mounted. If you are building your own API, you can implement the AbortController API in it to handle it.
For more context, the check if a component is mounted is an anti pattern as React is checking internally if the component is mounted to display that warning. Doing the same check again is just a way to hide the warning, and there are some easier ways to hide them than adding this piece of code on a big part of a codebase.
Source: https://medium.com/doctolib/react-stop-checking-if-your-component-is-mounted-3bb2568a4934

I had this warning possibly because of calling setState from an effect hook (This is discussed in these 3 issues linked together).
Anyway, upgrading the react version removed the warning.

React already removed this warning
but here is a better solution (not just workaround)
useEffect(() => {
const abortController = new AbortController() // creating an AbortController
fetch(url, { signal: abortController.signal }) // passing the signal to the query
.then(data => {
setState(data) // if everything went well, set the state
})
.catch(error => {
if (error.name === 'AbortError') return // if the query has been aborted, do nothing
throw error
})
return () => {
abortController.abort()
}
}, [])

The solution from #ford04 didn't worked to me and specially if you need to use the isMounted in multiple places (multiple useEffect for instance), it's recommended to useRef, as bellow:
Essential packages
"dependencies":
{
"react": "17.0.1",
}
"devDependencies": {
"typescript": "4.1.5",
}
My Hook Component
export const SubscriptionsView: React.FC = () => {
const [data, setData] = useState<Subscription[]>();
const isMounted = React.useRef(true);
React.useEffect(() => {
if (isMounted.current) {
// fetch data
// setData (fetch result)
return () => {
isMounted.current = false;
};
}
}
});

try changing setDivSizeThrottleable to
this.setDivSizeThrottleable = throttle(
() => {
if (this.isComponentMounted) {
this.setState({
pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
});
}
},
500,
{ leading: false, trailing: true }
);

I know that you're not using history, but in my case I was using the useHistory hook from React Router DOM, which unmounts the component before the state is persisted in my React Context Provider.
To fix this problem I have used the hook withRouter nesting the component, in my case export default withRouter(Login), and inside the component const Login = props => { ...; props.history.push("/dashboard"); .... I have also removed the other props.history.push from the component, e.g, if(authorization.token) return props.history.push('/dashboard') because this causes a loop, because the authorization state.
An alternative to push a new item to history.

Add a ref to a jsx component and then check it exist
function Book() {
const ref = useRef();
useEffect(() => {
asyncOperation().then(data => {
if (ref.current) setState(data);
})
});
return <div ref={ref}>content</div>
}

I had a similar issue thanks #ford04 helped me out.
However, another error occurred.
NB. I am using ReactJS hooks
ndex.js:1 Warning: Cannot update during an existing state transition (such as within `render`). Render methods should be a pure function of props and state.
What causes the error?
import {useHistory} from 'react-router-dom'
const History = useHistory()
if (true) {
history.push('/new-route');
}
return (
<>
<render component />
</>
)
This could not work because despite you are redirecting to new page all state and props are being manipulated on the dom or simply rendering to the previous page did not stop.
What solution I found
import {Redirect} from 'react-router-dom'
if (true) {
return <redirect to="/new-route" />
}
return (
<>
<render component />
</>
)

If you are fetching data from axios and the error still occurs, just wrap the setter inside the condition
let isRendered = useRef(false);
useEffect(() => {
isRendered = true;
axios
.get("/sample/api")
.then(res => {
if (isRendered) {
setState(res.data);
}
return null;
})
.catch(err => console.log(err));
return () => {
isRendered = false;
};
}, []);

I have 2 solutions for this error:
return:
If you are used hook and useEffect, So put a return end of useEffect.
useEffect(() => {
window.addEventListener('mousemove', logMouseMove)
return () => {
window.removeEventListener('mousemove', logMouseMove)
}
}, [])
componentWillUnmount:
If you are used componentDidMount, So put componentWillUnmount next to it.
componentDidMount() {
window.addEventListener('mousemove', this.logMouseMove)
}
componentWillUnmount() {
window.removeEventListener('mousemove', this.logMouseMove)
}

The isMounted approach is an anti-pattern in most cases because it doesn't actually clean up/cancel anything, it just avoids changing state on unmounted components, but does nothing with pending asynchronous tasks. The React team recently removed the leak warning because users keep creating a lot of anti-patterns to hide the warning rather than fix its cause.
But writing cancellable code in plain JS can be really tricky. To fix this I made my own lib useAsyncEffect2 with custom hooks, built on top of a cancellable promise (c-promise2) for executing cancellable async code to reach its graceful cancellation. All async stages (promises), including deep ones, are cancellable. This means that the request here will be automatically aborted if its parent context is canceled. Of course, any other asynchronous operation can be used instead of a request.
useAsyncEffect Demo with plain useState usage (Live Demo):
import React, { useState } from "react";
import { useAsyncEffect } from "use-async-effect2";
import cpAxios from "cp-axios";
function TestComponent({url}) {
const [text, setText] = useState("");
const cancel = useAsyncEffect(
function* () {
setText("fetching...");
const json = (yield cpAxios(url)).data;
setText(`Success: ${JSON.stringify(json)}`);
},
[url]
);
return (
<div>
<div>{text}</div>
<button onClick={cancel}>
Cancel request
</button>
</div>
);
}
useAsyncEffect Demo with internal states usage (Live Demo):
import React from "react";
import { useAsyncEffect } from "use-async-effect2";
import cpAxios from "cp-axios";
function TestComponent({ url, timeout }) {
const [cancel, done, result, err] = useAsyncEffect(
function* () {
return (yield cpAxios(url).timeout(timeout)).data;
},
{ states: true, deps: [url] }
);
return (
<div>
{done ? (err ? err.toString() : JSON.stringify(result)) : "loading..."}
<button onClick={cancel} disabled={done}>
Cancel async effect (abort request)
</button>
</div>
);
}
Class component using decorators (Live demo)
import React, { Component } from "react";
import { ReactComponent } from "c-promise2";
import cpAxios from "cp-axios";
#ReactComponent
class TestComponent extends Component {
state = {
text: ""
};
*componentDidMount(scope) {
const { url, timeout } = this.props;
const response = yield cpAxios(url).timeout(timeout);
this.setState({ text: JSON.stringify(response.data, null, 2) });
}
render() {
return (<div>{this.state.text}</div>);
}
}
export default TestComponent;
More other examples:
Axios request with errors handling
Fetch weather by coords
Live search
Pause & Resume
Progress capturing

Edit: I just realized the warning is referencing a component called TextLayerInternal. That's likely where your bug is. The rest of this is still relevant, but it might not fix your problem.
1) Getting the instance of a component for this warning is tough. It looks like there is some discussion to improve this in React but there currently is no easy way to do it. The reason it hasn't been built yet, I suspect, is likely because components are expected to be written in such a way that setState after unmount isn't possible no matter what the state of the component is. The problem, as far as the React team is concerned, is always in the Component code and not the Component instance, which is why you get the Component Type name.
That answer might be unsatisfactory, but I think I can fix your problem.
2) Lodashes throttled function has a cancel method. Call cancel in componentWillUnmount and ditch the isComponentMounted. Canceling is more "idiomatically" React than introducing a new property.

UPDATE DO NOT USE MY ORIGINAL ANSWER AS IT DOES NOT WORK
This answer was based on the use of cancelable promises and a note in makecancelable which I migrated to use hooks. However, it appears it does not cancel a chain of async/await and even cancelable-promise does not support canceling of a chain of awaits
Doing a bit more research on this, it appears that some internal Google reasons prevented cancelable promises from coming into the standard.
Further more, there was some promise with Bluebird which introduces cancelable promises, but it does not work in Expo or at least I haven't seen an example of it working in Expo.
The accepted answer is the best. Since I use TypeScript I had adapted the code with a few modifications (I explicitly set the dependencies since the accepted answer's implicit dependencies appear to give a re-render loop on my app, added and use async/await rather than promise chain, pass a ref to the mounted object so that an async/await chain can be canceled earlier if needed)
/**
* This starts an async function and executes another function that performs
* React state changes if the component is still mounted after the async
* operation completes
* #template T
* #param {(mountedRef: React.MutableRefObject<boolean>) => Promise<T>} asyncFunction async function,
* it has a copy of the mounted ref so an await chain can be canceled earlier.
* #param {(asyncResult: T) => void} onSuccess this gets executed after async
* function is resolved and the component is still mounted
* #param {import("react").DependencyList} deps
*/
export function useAsyncSetEffect(asyncFunction, onSuccess, deps) {
const mountedRef = useRef(false);
useEffect(() => {
mountedRef.current = true;
(async () => {
const x = await asyncFunction(mountedRef);
if (mountedRef.current) {
onSuccess(x);
}
})();
return () => {
mountedRef.current = false;
};
}, deps);
}
Original answer
Since I have many different operations that are async, I use the cancelable-promise package to resolve this issue with minimal code changes.
Previous code:
useEffect(() =>
(async () => {
const bar = await fooAsync();
setSomeState(bar);
})(),
[]
);
New code:
import { cancelable } from "cancelable-promise";
...
useEffect(
() => {
const cancelablePromise = cancelable(async () => {
const bar = await fooAsync();
setSomeState(bar);
})
return () => cancelablePromise.cancel();
},
[]
);
You can alsowrpte it in a custom utility function like this
/**
* This wraps an async function in a cancelable promise
* #param {() => PromiseLike<void>} asyncFunction
* #param {React.DependencyList} deps
*/
export function useCancelableEffect(asyncFunction, deps) {
useEffect(() => {
const cancelablePromise = cancelable(asyncFunction());
return () => cancelablePromise.cancel();
}, deps);
}

In my case of a login-like screen, the fetch was done in a onClick handler of a parent component, who passed that handler down to the child, whom placed .catch and .finally on it.
In the .then case a redirect (and hence unmount) would happen as normal operation, and only in cases of fetch error would the child stay mounted on-screen.
My solution was moving the setState and all other code from the .finally to the .catch since the child is guaranteed to be mounted in the .catch case. And in the .then case nothing needed doing because of the guaranteed unmount.

Based on #ford04 answer, here is the same encapsulated in a method :
import React, { FC, useState, useEffect, DependencyList } from 'react';
export function useEffectAsync( effectAsyncFun : ( isMounted: () => boolean ) => unknown, deps?: DependencyList ) {
useEffect( () => {
let isMounted = true;
const _unused = effectAsyncFun( () => isMounted );
return () => { isMounted = false; };
}, deps );
}
Usage:
const MyComponent : FC<{}> = (props) => {
const [ asyncProp , setAsyncProp ] = useState( '' ) ;
useEffectAsync( async ( isMounted ) =>
{
const someAsyncProp = await ... ;
if ( isMounted() )
setAsyncProp( someAsyncProp ) ;
});
return <div> ... ;
} ;

Depending on how you open your webpage, you may not be causing a mounting. Such as using a <Link/> back to a page that was already mounted in the virtual DOM, so requiring data from a componentDidMount lifecycle is caught.

Here is a simple solution for this. This warning is due to when we do some fetch request while that request is in the background (because some requests take some time.)and we navigate back from that screen then they react cannot update the state. here is the example code for this. write this line before every state Update.
if(!isScreenMounted.current) return;
Here is the Complete Code
import React , {useRef} from 'react'
import { Text,StatusBar,SafeAreaView,ScrollView, StyleSheet } from 'react-native'
import BASEURL from '../constants/BaseURL';
const SearchScreen = () => {
const isScreenMounted = useRef(true)
useEffect(() => {
return () => isScreenMounted.current = false
},[])
const ConvertFileSubmit = () => {
if(!isScreenMounted.current) return;
setUpLoading(true)
var formdata = new FormData();
var file = {
uri: `file://${route.params.selectedfiles[0].uri}`,
type:`${route.params.selectedfiles[0].minetype}`,
name:`${route.params.selectedfiles[0].displayname}`,
};
formdata.append("file",file);
fetch(`${BASEURL}/UploadFile`, {
method: 'POST',
body: formdata,
redirect: 'manual'
}).then(response => response.json())
.then(result => {
if(!isScreenMounted.current) return;
setUpLoading(false)
}).catch(error => {
console.log('error', error)
});
}
return(
<>
<StatusBar barStyle="dark-content" />
<SafeAreaView>
<ScrollView
contentInsetAdjustmentBehavior="automatic"
style={styles.scrollView}>
<Text>Search Screen</Text>
</ScrollView>
</SafeAreaView>
</>
)
}
export default SearchScreen;
const styles = StyleSheet.create({
scrollView: {
backgroundColor:"red",
},
container:{
flex:1,
justifyContent:"center",
alignItems:"center"
}
})

I solved this problem by providing all the params that are used in the useEffect hook
The code reported the bug:
useEffect(() => {
getDistrict({
geonameid: countryId,
subdistrict: level,
}).then((res) => {
......
});
}, [countryId]);
The code after fix:
useEffect(() => {
getDistrict({
geonameid: countryId,
subdistrict: level,
}).then((res) => {
......
});
}, [countryId,level]);
Can see that , problems solved after I provided all the params(including the level param) that supposed to pass through.

I had a similar problem and solved it :
I was automatically making the user logged-in by dispatching an action on redux
( placing authentication token on redux state )
and then I was trying to show a message with this.setState({succ_message: "...")
in my component.
Component was looking empty with the same error on console : "unmounted component".."memory leak" etc.
After I read Walter's answer up in this thread
I've noticed that in the Routing table of my application ,
my component's route wasn't valid if user is logged-in :
{!this.props.user.token &&
<div>
<Route path="/register/:type" exact component={MyComp} />
</div>
}
I made the Route visible whether the token exists or not.

In my case the issue was that the parent component was hidding the child because of a condition change in the child component.
So what I did was to change the condition so the child component was always shown.
What was happening:
const ParentComponent:FC = () => {
...
if (someCondition) {
return null;
}
return (
<>
Some cool text here
<ChildModalComponent message="this is a cool modal" />
</>
)
}
const ChildModalComponent: FC = () => {
...
const handleSubmit = () => {
setSomeCondition(true);
}
}
So after clicking submit the modal was automatically hidden becasue of the parent condition (someCondition).
How did I fix it?
I changed the place where the someCondition was checked in the Parent component, so the child component was always shown:
const ParentComponent:FC = () => {
...
return (
<>
{!someCondition && <>Some cool text here</>
<ChildModalComponent message="this is a cool modal" />
</>
)
}

I faced same warning, not it is fixed. To fix the issue, I removed the useRef() variable check in useEffect()
Earlier, the code was
const varRef = useRef();
useEffect(() => {
if (!varRef.current)
{
}
}, []);
Now, the code is
const varRef = useRef();
useEffect(() => {
//if (!varRef.current)
{
}
}, [])
Hope, it helps...

Inspired by the accepted answer by #ford04 I had even better approach dealing with it, instead of using useEffect inside useAsync create a new function that returns a callback for componentWillUnmount :
function asyncRequest(asyncRequest, onSuccess, onError, onComplete) {
let isMounted=true
asyncRequest().then((data => isMounted ? onSuccess(data):null)).catch(onError).finally(onComplete)
return () => {isMounted=false}
}
...
useEffect(()=>{
return asyncRequest(()=>someAsyncTask(arg), response=> {
setSomeState(response)
},onError, onComplete)
},[])

const handleClick = async (item: NavheadersType, index: number) => {
const newNavHeaders = [...navheaders];
if (item.url) {
await router.push(item.url); =>>>> line causing error (causing route to happen)
// router.push(item.url); =>>> coreect line
newNavHeaders.forEach((item) => (item.active = false));
newNavHeaders[index].active = true;
setnavheaders([...newNavHeaders]);
}
};

The simplest and most compact solution (with an explanation) is seen below as a one-liner solution.
useEffect(() => { return () => {}; }, []);
The useEffect() example above returns a callback function triggers React to finish its unmount portion of its life-cycle prior to updating state.
That very simplistic solution is all that is needed. In addition, it also works unlike the fictional syntax provided by #ford04 and #sfletche . By the way, the below code snippet from #ford04 is purely imaginary syntax (#sfletche , #vinod , #guneetgstar , and #Drew Cordano used the very same imaginary syntax).
data => {       <--- Fictional/Imaginary Syntax
someAsyncOperation().then(data => {
if (isMounted) setState(data); // add conditional check
})
All of my linters and all the linters of my entire team will not accept it and they report Uncaught SyntaxError: unexpected token: '=>'. I am surprised that no one caught the imaginary syntax. Would anyone who has participated in this question-thread, particularly among the up-voters, explain to me how they got the solutions to work for them?

Inspired by #ford04 answer I use this hook, which also takes callbacks for success, errors, finally and an abortFn:
export const useAsync = (
asyncFn,
onSuccess = false,
onError = false,
onFinally = false,
abortFn = false
) => {
useEffect(() => {
let isMounted = true;
const run = async () => {
try{
let data = await asyncFn()
if (isMounted && onSuccess) onSuccess(data)
} catch(error) {
if (isMounted && onError) onSuccess(error)
} finally {
if (isMounted && onFinally) onFinally()
}
}
run()
return () => {
if(abortFn) abortFn()
isMounted = false
};
}, [asyncFn, onSuccess])
}
If the asyncFn is doing some kind of fetch from back-end it often makes sense to abort it when the component is unmounted (not always though, sometimes if ie. you're loading some data into a store you might as well just want to finish it even if component is unmounted)