I’ve been experimenting with React’s new Concurrent Mode and encountered an unusual issue when combining it with the Context API. My application needs to handle frequent context changes, and I aimed to optimize this with Concurrent Mode, but it led to an unexpected re-rendering loop under specific conditions. Here’s a simplified version of my setup:
AppContext.js:
import React, { createContext, useState, useContext } from 'react';
const AppContext = createContext();
export const AppProvider = ({ children }) => {
const [count, setCount] = useState(0);
const increment = () => {
setCount((prevCount) => prevCount + 1);
};
return (
<AppContext.Provider value={{ count, increment }}>
{children}
</AppContext.Provider>
);
};
export const useAppContext = () => useContext(AppContext);
Counter.js:
import React from 'react';
import { useAppContext } from './AppContext';
const Counter = () => {
const { count, increment } = useAppContext();
console.log('Counter render:', count);
return (
<div>
<p>{count}</p>
<button onClick={increment}>Increment</button>
</div>
);
};
export default Counter;
App.js:
import React from 'react';
import { AppProvider } from './AppContext';
import Counter from './Counter';
const App = () => {
return (
<AppProvider>
<Counter />
</AppProvider>
);
};
export default App;
When running this code, I noticed that the Counter component enters a re-rendering loop when the button is clicked. This happens only when Concurrent Mode is enabled. Without Concurrent Mode, the component behaves as expected, re-rendering only once per click.
Here are the steps to reproduce:
Enable React’s Concurrent Mode in your project.
Implement the provided code.
Click the ‘Increment’ button in the Counter component.
Expected behavior:
The count should increment by 1, and the Counter component should re-render once per click.
Observed behavior:
The Counter component re-renders continuously in a loop after a single click.
I’m puzzled about why this looping behavior occurs with Concurrent Mode. Has anyone faced a similar issue, or does anyone have insights into what might be causing this and how to fix it?
Thank you for your help!
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