Exploring React New Features and Code Examples

React 19 is here, and it’s packed with features aimed at enhancing developer experience and application performance. From optimizing code to introducing powerful new hooks, React 19 continues to solidify its position as the go-to library for building modern web applications. Let’s dive into the key features and explore how they can revolutionize your development process with practical code examples.

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Key Features of React 19

1. The React Compiler

The new React Compiler simplifies and optimizes your code by transforming it into highly efficient JavaScript. This eliminates the need for manual performance tweaks like memoization, letting developers focus on building features rather than fine-tuning performance.

Example:

// Before: Manual optimization with useCallback
const MemoizedComponent = React.useCallback(() => {
  return <div>Optimized!</div>;
}, []);

// After: Automatically optimized
function Component() {
  return <div>Optimized!</div>;
}

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2. Server Components

Server Components in React 19 reduce the amount of JavaScript sent to the client by rendering components on the server. This improves performance and enables faster page loads.

Example:

// ServerComponent.server.jsx
export default function ServerComponent() {
  return <div>This is rendered on the server.</div>;
}

// App.jsx
import ServerComponent from './ServerComponent.server';

function App() {
  return (
    <div>
      <h1>Welcome to React 19</h1>
      <ServerComponent />
    </div>
  );
}

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3. Actions

Actions simplify state updates and error handling. By marking functions with a "use action" directive, React manages pending states, errors, and optimistic updates automatically.

Example:

function UpdateName() {
  const [name, setName] = useState('');

  const handleSubmit = async () => {
    'use action';
    await updateName(name);
  };

  return (
    <form onSubmit={handleSubmit}>
      <input type="text" value={name} onChange={(e) => setName(e.target.value)} />
      <button type="submit">Submit</button>
    </form>
  );
}

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4. New Hooks: use(), useFormStatus(), and useOptimistic()

use() for Data Fetching

The use() hook allows developers to handle promises directly within components.

Example:

function DataFetchingComponent() {
  const data = use(fetchData());

  return (
    <div>
      <h1>Data:</h1>
      <pre class="brush:php;toolbar:false">{JSON.stringify(data, null, 2)}