Develop Reference

React elements are removed on state update

I'm supposed to have a modal appear with an image in it. There are next and previous buttons which controls which image you are currently viewing. The modal is rendered in a portal. That in itself is working correctly. However, when I add children, and those childrens are updated, the modal only (not the portal) gets removed from the flow. In the React DevTools, the "isOpen" state of the modal is still set to true. I am using React 17.0.2 with NextJS 12.0.4 and Styled Components 5.3.3.
I have tried:
memoizing my components (as you can see there are some remnants of those trials) but this did not work
extracting the state of the modal to the parent and passing it as props and it didn't work either
I know there must be something wrong that I'm doing here so if you could help me find it that would be much appreciated!
Here is the controller where the modal is rendered:
import { FC, MouseEventHandler, useEffect, useState } from "react";
import { Photo } from "services/Images/Images.interfaces";
import { useGetNextPhoto, useGetPhotos, useGetPreviousPhoto } from "state";
import SlideshowContextProvider from "./Context/SlideshowContext";
import SlideShowModal from "./SlideShowModal";
const SlideshowController: FC = () => {
const photos = useGetPhotos();
const [currentlyViewedPhoto, setCurrentlyViewedPhoto] = useState<Photo | null>(null);
const nextPhoto = useGetNextPhoto(currentlyViewedPhoto?.id);
const previousPhoto = useGetPreviousPhoto(currentlyViewedPhoto?.id);
const onPreviousRequest: MouseEventHandler<HTMLButtonElement> = (event) => {
event.preventDefault();
setCurrentlyViewedPhoto(previousPhoto);
};
const onNextRequest: MouseEventHandler<HTMLButtonElement> = async (event) => {
event.preventDefault();
setCurrentlyViewedPhoto(nextPhoto);
};
useEffect(() => {
setCurrentlyViewedPhoto(photos[0]);
}, [photos]);
return (
<SlideshowContextProvider
currentlyViewing={currentlyViewedPhoto}
onNextSlideRequest={onNextRequest}
onPreviousSlideRequest={onPreviousRequest}
>
<SlideShowModal />
</SlideshowContextProvider>
);
};
export default SlideshowController;
The SlideshowModal:
import { Modal } from "components";
import { FC } from "react";
import SlideshowControlBar from "./SlideshowControlBar";
import SlideshowImage from "./SlideshowImage";
const SlideShowModal: FC = () => {
return (
<Modal uniqueKey="slideshow">
<SlideshowImage />
<SlideshowControlBar />
</Modal>
);
};
export default SlideShowModal;
The modal in itself:
import Portal from "components/Portal/Portal";
import { FC, useEffect, useMemo, useState } from "react";
import { useRegisterModal } from "state";
import styled from "styled-components";
import useWindowScrollLock from "./hook/UseWindowScrollLock";
interface Props {
uniqueKey: string;
isBackgroundOpaque?: boolean;
}
... Styled elements
const Modal: FC<Props> = ({ uniqueKey, isBackgroundOpaque = true, children }) => {
const [isOpen, setIsOpen] = useState(false);
const open = () => setIsOpen(true);
const close = () => setIsOpen(false);
const register = useRegisterModal(uniqueKey);
const isModalOpen = useMemo(() => isOpen, [isOpen]);
useEffect(() => {
register({ open, close });
}, [register]);
useWindowScrollLock(isModalOpen);
return isModalOpen ? (
<Portal>
<Container>
<InnerModal>
<Close onClick={close}>X</Close>
{children}
</InnerModal>
</Container>
<Background onClick={close} opaque={isBackgroundOpaque} />
</Portal>
) : null;
};
export default Modal;

React useEffect and React-Query useQuery issue?

I'm still new to React so forgive me if this is a silly approach to this problem.
My goal: Global error handling using a context provider and a custom hook.
The Problem: I can't remove errors without them immediately being re-added.
I display my errors via this component in the shell...
import React, { useState, useEffect } from 'react'
import Alert from '#mui/material/Alert'
import Collapse from '#mui/material/Collapse'
import { useAlertContext } from '#/context/alert-context/alert-context'
export default function AppAlert () {
const [show, setShow] = useState(false)
const alertContext = useAlertContext()
const handleClose = () => {
alertContext.remove()
setShow(false)
}
useEffect(() => {
if (alertContext.alert) {
setShow(true)
}
}, [alertContext.alert])
return (
<Collapse in={show}>
<Alert severity='error' onClose={handleClose}>
{alertContext.alert}
</Alert>
</Collapse>
)
}
I have a provider setup that also exposes a custom hook...
import React, { useState, createContext, useContext } from 'react'
const AlertContext = createContext()
const AlertProvider = ({ children }) => {
const [alert, setAlert] = useState(null)
const removeAlert = () => setAlert(null)
const addAlert = (message) => setAlert(message)
return (
<AlertContext.Provider value={{
alert,
add: addAlert,
remove: removeAlert
}}
>
{children}
</AlertContext.Provider>
)
}
const useAlertContext = () => {
return useContext(AlertContext)
}
export {
AlertProvider as default,
useAlertContext
}
And finally I have a hook setup to hit an API and call throw errors if it any occur while fetching the data. I'm purposely triggering a 404 by passing a bad API path.
import { useEffect } from 'react'
import { useQuery } from 'react-query'
import ApiV4 from '#/services/api/v4/base'
import { useAlertContext } from '#/context/alert-context/alert-context'
export const useAccess = () => {
const alertContext = useAlertContext()
const route = '/accessx'
const query = useQuery(route, async () => await ApiV4.get(route), {
retry: 0
})
useEffect(() => {
if (query.isError) {
alertContext.add(query.error.toString())
}
}, [alertContext, query.isError, query.error])
return query
}
This code seems to be the issue. Because alertContext.remove() triggers useEffect here and query.error still exists, it immediately re-adds the error to the page on remove. Removing alertContext from the array works, but it is not a real fix and linter yells.
useEffect(() => {
if (query.isError) {
alertContext.add(query.error.toString())
}
}, [alertContext, query.isError, query.error])

This is a perfectly fine approach to the problem. You've also accurately identified the problem. The solution is to create a second hook with access to the methods that will modify the context. AppAlert needs access to the data in the context, and needs to update when AlertContext.alert changes. UseAccess only needs to be able to call AlertContext.add, and that method wont change and trigger a re-render. This can be done with a second Context. You can just expose one Provider and bake the actions provider into the outer context provider.
import React, { useState, createContext, useContext } from 'react'
const AlertContext = createContext()
const AlertContextActions = createContext()
const AlertProvider = ({ children }) => {
const [alert, setAlert] = useState(null)
const removeAlert = () => setAlert(null)
const addAlert = (message) => setAlert(message)
return (
<AlertContext.Provider value={{ alert }}>
<AlertContextActions.Provider value={{ addAlert, removeAlert }}>
{children}
</AlertContextActions.Provider>
</AlertContext.Provider>
)
}
const useAlertContext = () => {
return useContext(AlertContext)
}
export {
AlertProvider as default,
useAlertContext
}
Now, where you need access to the alert you use one hook and where you need access to the actions you use the other.
// in AppAlert
import { useAlertContext, useAlertContextActions } from '#/context/alert-context/alert-context'
...
const { alert } = useAlertContext()
const { removeAlert } = useAlertContextActions()
And finally
// in useAccess
import { useAlertContextActions } from '#/context/alert-context/alert-context'
...
const { addAlert } = useAlertContextActions()

So I found a solution that seems to work for my purposes. I got a hint from this article. https://mortenbarklund.com/blog/react-architecture-provider-pattern/
Note the use of useCallback above. It ensures minimal re-renders of components using this context, as the function is guaranteed to be stable (as its memoized without dependencies).
So with this I tried the following and it solved the problem.
import React, { useState, createContext, useContext, useCallback } from 'react'
const AlertContext = createContext()
const AlertProvider = ({ children }) => {
const [alert, setAlert] = useState(null)
const removeAlert = useCallback(() => setAlert(null), [])
const addAlert = useCallback((message) => setAlert(message), [])
return (
<AlertContext.Provider value={{
alert,
add: addAlert,
remove: removeAlert
}}
>
{children}
</AlertContext.Provider>
)
}
const useAlertContext = () => {
return useContext(AlertContext)
}
export {
AlertProvider as default,
useAlertContext
}

My goal: Global error handling
One problem with the above useEffect approach is that every invocation of useAccess will run their own effects. So if you have useAccess twice on the page, and it fails, you will get two alerts, so it's not really "global".
I would encourage you to look into the global callbacks on the QueryCache in react-query. They are made for this exact use-case: To globally handle errors. Note that to use context, you would need to create the queryClient inside the Application, and make it "stable" with either useRef or useState:
function App() {
const alertContext = useAlertContext()
const [queryClient] = React.useState(() => new QueryClient({
queryCache: new QueryCache({
onError: (error) =>
alertContext.add(error.toString())
}),
}))
return (
<QueryClientProvider client={queryClient}>
<RestOfMyApp />
</QueryClientProvider>
)
}
I also have some examples in my blog.

NextJS: Pass string via context from input into getStaticProps

I´m new to NextJS and React at all so I ask for your forgiveness.
I want to know how to pass an users written text from an input field (inside of Header) into the getStaticProbs function of a specific page via the react context api.
I tried the following source but it doesn`t work - it throws out an error that my way to build leads to an invalid hook call.
Here is my context source:
import React, { createContext, useState } from 'react';
export const SearchContext = createContext();
export const SearchProvider = ({ children }) => {
const [keyword, setKeyword] = useState('');
return (
<SearchContext.Provider
value={{
keyword,
setKeyword,
}}
>
{children}
</SearchContext.Provider>
);
};
to fetch the written string of SearchBar.js:
import React, { useContext, useState } from 'react';
import { useRouter } from 'next/router';
import Image from 'next/image';
import loupe from '../public/images/loupe.png';
import { SearchContext } from '../lib/searchCtx';
const SearchBar = () => {
const search = useContext(SearchContext);
const router = useRouter();
const submitAction = (e) => {
e.preventDefault();
router.push(`/searchResults`);
};
return (
<div className={styles.searchBar}>
<input
type='text'
placeholder='Suche...'
onChange={(e) => search.setKeyword(e.target.value)}
/>
<button className={styles.searchBtn} type='submit' onClick={submitAction}>
<Image src={loupe} alt='' />
</button>
</div>
);
};
export default SearchBar;
and pass it over _app.js:
import Header from '../components/Header';
import Footer from '../components/Footer';
import { SearchProvider } from '../lib/searchCtx';
function MyApp({ Component, pageProps }) {
return (
<>
<SearchProvider>
<Header />
<Component {...pageProps} />
</SearchProvider>
<Footer />
</>
);
}
}
export default MyApp;
to get the value into getStaticProbs of searchResults.js:
import { useEffect, useState, useContext } from 'react';
import { fetchData } from '../lib/utils';
import styles from '../styles/Playlist.module.scss';
import Image from 'next/image';
import { SearchContext } from '../lib/searchCtx';
export default function SearchResults({ videos }) {
console.log(videos);
const sortedVids = videos
.sort((a, b) =>
Number(
new Date(b.snippet.videoPublishedAt) -
Number(new Date(a.snippet.videoPublishedAt))
)
)
return (
<>
<div className={`${styles.playlist_container} ${styles.search}`}>
<h1>Search results</h1>
{sortedVids
.map((vid, id) => {
return (
<div className={styles.clip_container}>
<Image
className={styles.thumbnails}
src={vid.snippet.thumbnails.medium.url}
layout='fill'
objectFit='cover'
alt={vid.snippet.title}
/>
</div>
<div className={styles.details_container}>
<h3>{vid.snippet.title}</h3>
</div>
);
})}
</div>
</>
);
}
export async function getStaticProps() {
const search = useContext(SearchContext);
const { YOUTUBE_KEY } = process.env;
const uploadsURL = `https://youtube.googleapis.com/youtube/v3/search?part=snippet&channelId=UCbqKKcML7P4b4BDhaqdh_DA&maxResults=50&key=${YOUTUBE_KEY}&q=${search.keyword}`;
async function getData() {
const uploadsData = fetchData(uploadsURL);
return {
videos: await uploadsData,
};
}
const { videos } = await getData();
return {
revalidate: 86400,
props: {
videos: videos.items,
},
};
}
Would you help me by 1) telling me the main failure I did and 2) providing me a working source?
How can I achieve it to get the keyword from SearchContext into the uploadsURL (inside of getStaticProbs) or isn`t it possible?
Thanks in advance!!

You can create a dynamic pages under your page folder one called say index.js and one called [slug].js (all under one folder) In the index page you can have your normal search input, when the users submit the query you can do
<a
onClick={() =>
router
.push(`/movies/${search.keyword}`)
.then(() => window.scrollTo(0, 0))}>
search
</a>
and in your [slug].js page you can retrieve that information like so
export async function getServerSideProps(pageContext) {
const pageQuery = pageContext.query.slug;
const apiCall= await fetch(
``https://youtube.googleapis.com/youtube/v3/search?part=snippet&channelId=UCbqKKcML7P4b4BDhaqdh_DA&maxResults=50&key=${YOUTUBE_KEY}&q=${pageQuery}`
);
const results = await apiCall.json();
return {
props: {
data: results,
},
};
}
I don't know if this will work for you but is a solution

REST API Response Flickering on Page Load

I've got component that displays contact information from a dealer as chosen by the user. To be more specific, a user selects their location, setting a cookie which then is used to define the API call. I pull in the contact information of the dealer in that location using Axios, store it in a context, and then display the information as necessary through several components: the header, a "current location" component etc. However, I'm having an issue with the content flickering each time the page is refreshed.
I've tried storing the JSON response in local storage, but, for a brief moment on page load, it shows as undefined, making the flicker continue. Obviously, I'm needing to eliminate that so that the data persists.
I've got it working via ApiContext, and I'm displaying the data in my Header component. Below is the code for both:
ApiContext.tsx
import React, { createContext, useEffect, useState } from 'react';
import axios from 'axios';
const contextObject = {} as any;
export const context = createContext(contextObject);
export const ApiContext = ({ children }: any) => {
const [selectedDealer, setselectedDealer] = useState(`1`);
useEffect(() => {
axios
.get(`${process.env.GATSBY_API_ENDPOINT}/${selectedDealer}`)
.then((response) => setselectedDealer(response.data));
}, [selectedDealer]);
const changeDealer = (id: any) => {
setselectedDealer(id);
};
const { Provider } = context;
return (
<Provider value={{ data: selectedDealer, changeDealer: changeDealer }}>
{children}
</Provider>
);
};
Header.tsx
import React, { ReactNode, useContext, useEffect, useState } from 'react';
import Logo from 'assets/svg/logo.svg';
import css from 'classnames';
import { Button } from 'components/button/Button';
import { Link } from 'components/link/Link';
import { MenuIcon } from 'components/menu-icon/MenuIcon';
import { context } from 'contexts/ApiContext';
import { NotificationBar } from '../notification-bar/NotificationBar';
import s from './Header.scss';
import { MainNav } from './navigation/MainNav';
interface HeaderProps {
navigationContent: ReactNode;
}
export const Header = ({ navigationContent }: HeaderProps) => {
const [scrolled, setScrolled] = useState(false);
const [open, setOpen] = useState(false);
const data = useContext(context);
const buttonLabel = data ? data.name : 'Find a Dealer';
const buttonLink = data ? `tel:${data.phone}` : '/find-a-dealer';
useEffect(() => {
const handleScroll = () => {
const isScrolled = window.scrollY > 10;
if (isScrolled !== scrolled) {
setScrolled(!scrolled);
}
};
document.addEventListener('scroll', handleScroll, { passive: true });
return () => {
document.removeEventListener('scroll', handleScroll);
};
}, [scrolled]);
return (
<>
<NotificationBar notificationContent={navigationContent} />
<header className={scrolled ? css(s.header, s.header__scrolled) : s.header}>
<nav className={s.header__navigation}>
<ul className={s.header__container}>
<li className={s.header__logo}>
<Link to="/" className={s.header__link}>
<Logo />
</Link>
</li>
<li className={s.header__primary}>
<MainNav navigationItems={navigationContent} />
</li>
<li className={s.header__utility}>
<Button href={buttonLink}>{buttonLabel}</Button>
</li>
<li className={s.header__icon}>
<MenuIcon onClick={() => setOpen(!open)} />
</li>
</ul>
</nav>
</header>
</>
);
};
I would assume that this is because the API call is being triggered each time the page is refreshed, so I wonder if there's any way to persist the data in a more efficient way?
Thanks in advance!

Your ApiContext.tsxcould persist the data in localStorage is such a way:
import React, { createContext } from 'react';
import axios from 'axios';
import { makeUseAxios } from 'axios-hooks';
import { useCookie } from 'hooks/use-cookie';
const contextObject = {} as any;
export const context = createContext(contextObject);
const useAxios = makeUseAxios({
axios: axios.create({ baseURL: process.env.GATSBY_API_ENDPOINT }),
});
const loadData = (cookie) => {
const stored = localStorage.getItem("data");
const parsed = JSON.parse(stored);
// You can also store a lastSync timestamp along with the data, so that you can refresh them if necessary
if (parsed) return parsed;
const [{data}] = useAxios(`${cookie}`);
if (!isEqual(parsed, data)) {
localStorage.setItem('data', JSON.stringify(data));
}
return data
}
export const ApiContext = ({ children }: any) => {
const [cookie] = useCookie('one-day-location', '1');
const [{ data }] = loadData(cookie);
const { Provider } = context;
return <Provider value={data}>{children}</Provider>;
};
The above implementation will only fetch the data once, so remember to refresh them at some point inside your code and update the localStorage item, or use a timestamp to compare and force the api call as commented in my code.
Keep in mind that even this implementation may take a fraction of a second to be completed, so I would suggest to always use loaders/spinners/skeletons while your application is fetching the required data.

I got this worked out, using a hook that persists my state, storing it in a localStorage item.
usePersistState.ts
import { useEffect, useState } from 'react';
export const usePersistState = (key: string, defaultValue: string) => {
const [value, setValue] = useState(() => {
if (typeof window !== 'undefined') {
const stickyValue = window.localStorage.getItem(key);
return stickyValue !== null ? JSON.parse(stickyValue) : defaultValue;
}
});
useEffect(() => {
window.localStorage.setItem(key, JSON.stringify(value));
}, [key, value]);
return [value, setValue];
};
Then, in ApiContext, I set my default state, but when that state changes, it updates and persists the state. Here's my context component now:
ApiContext.tsx
import React, { createContext, useEffect } from 'react';
import { usePersistState } from 'hooks/use-persist-state';
import axios from 'axios';
const contextObject = {} as any;
export const context = createContext(contextObject);
const LOCAL_STORAGE_KEY_SELECTED_DEALER = 'selectedDealerInformation';
export const ApiContext = ({ children }: any) => {
const [selectedDealer, setselectedDealer] = usePersistState(LOCAL_STORAGE_KEY_SELECTED_DEALER, '1');
useEffect(() => {
axios
.get(`${process.env.GATSBY_API_ENDPOINT}/${selectedDealer}`)
.then((response) => setselectedDealer(response.data));
}, [selectedDealer]);
const changeDealer = (id: any) => {
setselectedDealer(id);
};
localStorage.setItem(LOCAL_STORAGE_KEY_SELECTED_DEALER, JSON.stringify(selectedDealer));
const { Provider } = context;
return (
<Provider value={{ data: selectedDealer, changeDealer: changeDealer }}>{children}</Provider>
);
};

React context not updating

I have set a basic sample project that use Context to store the page title, but when I set it the component is not rerendered.
Principal files:
Context.js
import React from 'react'
const Context = React.createContext({})
export default Context
AppWrapper.js
import React from 'react'
import App from './App'
import Context from './Context'
function AppWrapper () {
return (
<Context.Provider value={{page: {}}}>
<App />
</Context.Provider>
)
}
export default AppWrapper
App.js
import React, { useContext } from 'react';
import Context from './Context';
import Home from './Home';
function App() {
const { page } = useContext(Context)
return (
<>
<h1>Title: {page.title}</h1>
<Home />
</>
);
}
export default App;
Home.js
import React, { useContext } from 'react'
import Context from './Context'
function Home () {
const { page } = useContext(Context)
page.title = 'Home'
return (
<p>Hello, World!</p>
)
}
export default Home
full code
What am I doing wrong?

Think about React context just like you would a component, if you want to update a value and show it then you need to use state. In this case your AppWrapper where you render the context provider is where you need to track state.
import React, {useContext, useState, useCallback, useEffect} from 'react'
const PageContext = React.createContext({})
function Home() {
const {setPageContext, page} = useContext(PageContext)
// essentially a componentDidMount
useEffect(() => {
if (page.title !== 'Home')
setPageContext({title: 'Home'})
}, [setPageContext])
return <p>Hello, World!</p>
}
function App() {
const {page} = useContext(PageContext)
return (
<>
<h1>Title: {page.title}</h1>
<Home />
</>
)
}
function AppWrapper() {
const [state, setState] = useState({page: {}})
const setPageContext = useCallback(
newState => {
setState({page: {...state.page, ...newState}})
},
[state, setState],
)
const getContextValue = useCallback(
() => ({setPageContext, ...state}),
[state, updateState],
)
return (
<PageContext.Provider value={getContextValue()}>
<App />
</PageContext.Provider>
)
}
Edit - Updated working solution from linked repository
I renamed a few things to be a bit more specific, I wouldn't recommend passing setState through the context as that can be confusing and conflicting with a local state in a component. Also i'm omitting chunks of code that aren't necessary to the answer, just the parts I changed
src/AppContext.js
export const updatePageContext = (values = {}) => ({ page: values })
export const updateProductsContext = (values = {}) => ({ products: values })
export const Pages = {
help: 'Help',
home: 'Home',
productsList: 'Products list',
shoppingCart: 'Cart',
}
const AppContext = React.createContext({})
export default AppContext
src/AppWrapper.js
const getDefaultState = () => {
// TODO rehydrate from persistent storage (localStorage.getItem(myLastSavedStateKey)) ?
return {
page: { title: 'Home' },
products: {},
}
}
function AppWrapper() {
const [state, setState] = useState(getDefaultState())
// here we only re-create setContext when its dependencies change ([state, setState])
const setContext = useCallback(
updates => {
setState({ ...state, ...updates })
},
[state, setState],
)
// here context value is just returning an object, but only re-creating the object when its dependencies change ([state, setContext])
const getContextValue = useCallback(
() => ({
...state,
setContext,
}),
[state, setContext],
)
return (
<Context.Provider value={getContextValue()}>
...
src/App.js
...
import AppContext, { updateProductsContext } from './AppContext'
function App() {
const [openDrawer, setOpenDrawer] = useState(false)
const classes = useStyles()
const {
page: { title },
setContext,
} = useContext(Context)
useEffect(() => {
fetch(...)
.then(...)
.then(items => {
setContext(updateProductsContext({ items }))
})
}, [])
src/components/DocumentMeta.js
this is a new component that you can use to update your page names in a declarative style reducing the code complexity/redundancy in each view
import React, { useContext, useEffect } from 'react'
import Context, { updatePageContext } from '../Context'
export default function DocumentMeta({ title }) {
const { page, setContext } = useContext(Context)
useEffect(() => {
if (page.title !== title) {
// TODO use this todo as a marker to also update the actual document title so the browser tab name changes to reflect the current view
setContext(updatePageContext({ title }))
}
}, [title, page, setContext])
return null
}
aka usage would be something like <DocumentMeta title="Whatever Title I Want Here" />
src/pages/Home.js
each view now just needs to import DocumentMeta and the Pages "enum" to update the title, instead of pulling the context in and manually doing it each time.
import { Pages } from '../Context'
import DocumentMeta from '../components/DocumentMeta'
function Home() {
return (
<>
<DocumentMeta title={Pages.home} />
<h1>WIP</h1>
</>
)
}
Note: The other pages need to replicate what the home page is doing
Remember this isn't how I would do this in a production environment, I'd write up a more generic helper to write data to your cache that can do more things in terms of performance, deep merging.. etc. But this should be a good starting point.

Here is a working version of what you need.
import React, { useState, useContext, useEffect } from "react";
import "./styles.css";
const Context = React.createContext({});
export default function AppWrapper() {
// creating a local state
const [state, setState] = useState({ page: {} });
return (
<Context.Provider value={{ state, setState }}> {/* passing state to in provider */}
<App />
</Context.Provider>
);
}
function App() {
// getting the state from Context
const { state } = useContext(Context);
return (
<>
<h1>Title: {state.page.title}</h1>
<Home />
</>
);
}
function Home() {
// getting setter function from Context
const { setState } = useContext(Context);
useEffect(() => {
setState({ page: { title: "Home" } });
}, [setState]);
return <p>Hello, World!</p>;
}
Read more on Hooks API Reference.

You may put useContext(yourContext) at wrong place.
The right position is inner the <Context.Provider>:
// Right: context value will update
<Context.Provider>
<yourComponentNeedContext />
</Context.Provider>
// Bad: context value will NOT update
<yourComponentNeedContext />
<Context.Provider>
</Context.Provider>