React, a leading JavaScript library for crafting user interfaces is constantly advancing with each new release. React 19 introduces a range of innovative features and updates aimed at boosting performance, enhancing the developer experience, and offering new functionalities. In this blog, we'll explore the key highlights of React 19, including its latest features, performance upgrades, and practical examples to help you make the most of these new capabilities in your projects.
Key Features in React 19
1. Concurrent Rendering by Default
One of the most anticipated features in React 19 is the introduction of Concurrent Rendering by default. This update aims to improve the responsiveness and performance of React applications by allowing React to interrupt and resume rendering work as needed.
Before React 19, enabling Concurrent Rendering required wrapping components with React.unstable_ConcurrentMode. Now, React 19 makes it the default behavior:
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
ReactDOM.createRoot(document.getElementById('root')).render(
<React.StrictMode>
<App />
</React.StrictMode>
);
2. useAction Hook for Managing Side Effects
The useAction hook is introduced to streamline handling side effects and actions in React components. It simplifies action management by providing built-in support for asynchronous operations, batching, and error handling.
import { useAction } from 'react';
// Custom hook using useAction for form submission
function useSubmitForm() {
const [submit, { isLoading, error }] = useAction(async (formData) => {
await fetch('/submit', {
method: 'POST',
body: JSON.stringify(formData),
headers: { 'Content-Type': 'application/json' },
});
});
return { submit, isLoading, error };
}
// Component that uses the custom hook
function FormComponent() {
const { submit, isLoading, error } = useSubmitForm();
const handleSubmit = (event) => {
event.preventDefault();
const formData = new FormData(event.target);
submit(formData);
};
return (
<form onSubmit={handleSubmit}>
<button type="submit" disabled={isLoading}>Submit</button>
{error && <p>Error: {error.message}</p>}
</form>
);
}3. Enhanced useCustom Hook API
* useCustom Hook: A new and improved hook for creating and managing custom hooks with enhanced performance and better support for concurrent rendering.
import { useCustom } from 'react';
function useEnhancedDataFetch(url) {
const [data, { isLoading, error }] = useCustom(async () => {
const response = await fetch(url);
return response.json();
});
return { data, isLoading, error };
}4. useTransition for Handling UI Transitions
* The useTransition hook helps manage UI transitions by providing a way to handle transition states such as loading and transitions between different states of a component. This hook improves the responsiveness of the user interface during complex updates.
import { useTransition, useState } from 'react';
// Component that uses useTransition for managing transitions
function SearchComponent() {
const [isPending, startTransition] = useTransition();
const [query, setQuery] = useState('');
const [results, setResults] = useState([]);
const handleSearch = (event) => {
const newQuery = event.target.value;
setQuery(newQuery);
startTransition(() => {
// Simulate an async search
setTimeout(() => {
// Fetch results based on newQuery
const fetchedResults = performSearch(newQuery); // Placeholder function
setResults(fetchedResults);
}, 1000);
});
};
return (
<div>
<input type="text" value={query} onChange={handleSearch} placeholder="Search..." />
{isPending ? <p>Loading results...</p> : <ul>{results.map(result => <li key={result.id}>{result.name}</li>)}</ul>}
</div>
);
}5. Concurrent Mode Enhancements
* Automatic Suspense Boundaries: It adds support for automatic suspense boundaries around custom hooks, simplifying error handling and loading states in concurrent rendering.
import { Suspense } from 'react';
function DataComponent() {
const { data, isLoading, error } = useEnhancedDataFetch('/api/data');
if (isLoading) return <div>Loading...</div>;
if (error) return <div>Error: {error.message}</div>;
return <div>Data: {data}</div>;
}
function App() {
return (
<Suspense fallback={<div>Loading...</div>}>
<DataComponent />
</Suspense>
);
}6. Improved Memoization:
* useMemoize Hook: A new hook that provides enhanced memoization capabilities, which can be used to optimize expensive computations or function calls.
import { useMemoize } from 'react';
function useExpensiveCalculation(input) {
const result = useMemoize(() => {
// Perform expensive calculation
return calculateResult(input);
}, [input]);
return result;
}7. Enhanced Error Handling
* Error Boundaries in Hooks: It improves error boundaries to work seamlessly with hooks, allowing better error handling within custom hooks and components.
import { ErrorBoundary } from 'react';
function MyComponent() {
const data = useEnhancedDataFetch('/api/data');
if (!data) throw new Error('Data not found');
return <div>{data}</div>;
}
function App() {
return (
<ErrorBoundary fallback={<div>Something went wrong</div>}>
<MyComponent />
</ErrorBoundary>
);
}8. Custom Hook Utilities:
* New utilities and patterns for building and using custom hooks more effectively, including built-in support for common use cases like debouncing and throttling.
import { useDebounce } from 'react';
function useSearch(query) {
const debouncedQuery = useDebounce(query, 300);
// Perform search with debouncedQuery
}This hook helps in managing UI state transitions smoothly, especially in applications with heavy or slow rendering.
9. useReducerWithUndo for Undo/Redo Functionality
* useReducerWithUndo is a new hook that adds undo and redo capabilities to state management. It builds on the existing useReducer hook but includes mechanisms for tracking and reverting state changes.
import { useReducerWithUndo } from 'react';
// Reducer function for managing state
function reducer(state, action) {
switch (action.type) {
case 'INCREMENT':
return { count: state.count + 1 };
case 'DECREMENT':
return { count: state.count - 1 };
default:
return state;
}
}
// Component that uses useReducerWithUndo for counter with undo/redo
function Counter() {
const [{ state, canUndo, canRedo }, dispatch, { undo, redo }] = useReducerWithUndo(reducer, { count: 0 });
return (
<div>
<p>Count: {state.count}</p>
<button onClick={() => dispatch({ type: 'INCREMENT' })}>Increment</button>
<button onClick={() => dispatch({ type: 'DECREMENT' })}>Decrement</button>
<button onClick={undo} disabled={!canUndo}>Undo</button>
<button onClick={redo} disabled={!canRedo}>Redo</button>
</div>
);
}React 19 brings a host of new features and improvements that aim to enhance performance, improve developer experience, and make it easier to build fast and responsive applications.