Exploring the Latest Features in React 18

React has been a dominant player in the front-end development space for years, consistently pushing the boundaries of what web applications can achieve. The release of React 18 brings with it a slew of new features and improvements that are set to revolutionize the way developers build and optimize their applications.

1. Automatic Batching

One of the most anticipated features in React 18 is automatic batching. In previous versions, React would only batch state updates that occur within event handlers. However, with React 18, state updates from any context (including promises, timeouts, native event handlers, or any other event) will be batched automatically.

Example:

import { useState } from 'react';

function Counter() {
  const [count, setCount] = useState(0);
  const [flag, setFlag] = useState(false);

  const handleClick = () => {
    setTimeout(() => {
      setCount((c) => c + 1);
      setFlag((f) => !f);
    }, 1000);
  };

  return (
    <div>
      <button onClick={handleClick}>Increment</button>
      <p>Count: {count}</p>
      <p>Flag: {flag.toString()}</p>
    </div>
  );
}

In React 17, this would result in two separate renders, but in React 18, these state updates are automatically batched, resulting in a single render for better performance.

2. Concurrent Rendering

Concurrent rendering is a game-changer for React applications. It allows React to work on multiple tasks simultaneously, without blocking the main thread. This means that your application remains responsive even during heavy computations or rendering tasks.

Concurrent rendering is opt-in and can be enabled by wrapping your component tree with the ConcurrentMode component.

Example:

import { createRoot } from 'react-dom/client';
import App from './App';

const root = createRoot(document.getElementById('root'));
root.render(
  <ConcurrentMode>
    <App />
  </ConcurrentMode>
);

3. Transitions

Transitions are a new way to differentiate between urgent and non-urgent updates. This feature is particularly useful for improving the user experience in scenarios where you want to prioritize certain updates over others.

Example:

import { useState, startTransition } from 'react';

function SearchComponent() {
  const [query, setQuery] = useState('');
  const [results, setResults] = useState([]);

  const handleChange = (e) => {
    const newQuery = e.target.value;
    setQuery(newQuery);
    startTransition(() => {
      const newResults = performSearch(newQuery); // performSearch is a function that returns search results
      setResults(newResults);
    });
  };

  return (
    <div>
      <input type="text" value={query} onChange={handleChange} />
      <ul>
        {results.map((result) => (
          <li key={result.id}>{result.name}</li>
        ))}
      </ul>
    </div>
  );
}

Using startTransition, you can mark updates as non-urgent, allowing React to prioritize other more critical updates first.

4. useDeferredValue and useId

React 18 introduces two new hooks: useDeferredValue and useId.

• useDeferredValue: This hook is used to defer a value and optimize rendering. It can be useful for improving performance in scenarios where you need to debounce or throttle updates.
• useId: This hook generates a unique ID that is stable across the entire component lifecycle. It’s particularly useful for form elements and accessibility features.

Example:

import { useDeferredValue, useId } from 'react';

function DeferredComponent({ input }) {
  const deferredInput = useDeferredValue(input);
  const id = useId();

  return (
    <div>
      <label htmlFor={id}>Deferred Input:</label>
      <input id={id} value={deferredInput} readOnly />
    </div>
  );
}

5. SSR and Streaming Improvements

React 18 also brings significant improvements to server-side rendering (SSR) and streaming. These enhancements include support for streaming SSR, allowing React to send parts of the HTML to the client as they are ready. This results in faster time-to-first-byte (TTFB) and improved overall performance.

Example:

import { renderToPipeableStream } from 'react-dom/server';
import App from './App';
import { Readable } from 'stream';

const stream = new Readable();
const { pipe } = renderToPipeableStream(<App />, {
  onShellReady() {
    stream.pipe(res);
  },
});

pipe(stream);

Conclusion

React 18 is packed with features that enhance performance, improve developer experience, and provide more flexibility for building modern web applications. From automatic batching and concurrent rendering to new hooks and SSR improvements, there’s a lot to explore and integrate into your projects.