React is a popular library for building user interfaces that is written in JavaScript. With the release of React 18, developers now have access to a number of new features and improvements that make their work easier and improve the performance of the user interface. In this article, we'll look at some of the new features in React 18.

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Table of Contents:

1. Concurrent Rendering
2. Automatic Batching of State Updates
3. Improved Error Handling
4. Improved Server-Side Rendering

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Concurrent Rendering

Concurrent Rendering is one of the most important changes that React 18 brings. This feature lets components be rendered at different times, so the browser can show content as it becomes ready instead of waiting for the whole page to load. This makes the page load faster and makes it easier to use. With Concurrent Rendering, you can break up complicated user interfaces into smaller pieces and render each of them at the same time, instead of waiting for one part to finish before moving on to the next.

For example, let's say you have a complicated dashboard with several parts that need to load data from a backend server. With Concurrent Rendering, you can show the user the parts of the user interface that don't need server data first. As soon as the server data is ready, you can render the parts that need it. This way, your users won't have to wait for the whole page to load before they can start using the application.

function MyDashboard() {
  const [data, setData] = useState(null);
  const [error, setError] = useState(null);

  useEffect(() => {
    fetchData().then((response) => setData(response)).catch((err) => setError(err));
  }, []);

  return (
    <div>
      <Header />
      {data ? (
        <React.Suspense fallback={<Spinner />}>
          <DashboardChart data={data} />
          <DashboardTable data={data} />
        </React.Suspense>
      ) : (
        error ? <ErrorMessage error={error} /> : <Spinner />
      )}
    </div>
  );
}

Concurrent Rendering

In this example, we use React.Suspense to render the DashboardChart and DashboardTable components asynchronously, only when the data has been loaded from the backend. This way, the user will see a spinner until the data is ready, but won't have to wait for everything to be loaded before they can interact with the UI.

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Automatic Batching of State Updates

Automatic batching of state updates is another thing that was added in React 18. This means that when multiple changes to the state happen in the same event loop, React will automatically group these changes together so that the page doesn't have to be re-rendered more than it needs to. This improvement helps cut down on the number of re-renders and improve performance as a whole.

For example, say you have a component whose state needs to change when a user does something like click a button. With automatic batching, React will wait until all state updates are done before re-rendering the component. This way, you can avoid re-rendering when it's not necessary and make your app run faster.

function MyComponent() {
  const [count, setCount] = useState(0);
  const [message, setMessage] = useState("");

  function handleClick() {
    setCount((prevCount) => prevCount + 1);
    setMessage(`You clicked the button ${count + 1} times`);
  }

  return (
    <div>
      <button onClick={handleClick}>Click me</button>
      <p>{message}</p>
    </div>
  );
}

Automatic Batching of State Updates

In this example, when a button is clicked, two states are changed. With automatic batching, React will automatically group these updates together, so that the message will be updated with the correct count value.

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Improved Error Handling

Error handling has been improved in React 18. React now gives more detailed error messages when a problem happens in a component, making it easier to find and fix problems. Also, React now supports a new Error Boundary API that lets developers catch and handle errors within a component tree.

For example, say you have a component that loads data from a backend server. If the server isn't working or the data is wrong, the component may throw an error. With the new Error Boundary API, you can catch this error and show the user a helpful message instead of crashing the entire application.

class ErrorBoundary extends React.Component {
  constructor(props) {
    super(props);
    this.state = { hasError: false, error: null };
  }

  static getDerivedStateFromError(error) {
    return { hasError: true, error: error };
  }

  componentDidCatch(error, info) {
    console.error("Error caught by ErrorBoundary:", error, info);
  }

  render() {
    if (this.state.hasError) {
      return <ErrorMessage error={this.state.error} />;
    }

    return this.props.children;
  }
}

function MyComponent() {
  return (
    <div>
      <ErrorBoundary>
        <ComponentThatMightThrowAnError />
      </ErrorBoundary>
    </div>
  );
}

Improved Error Handling

In this example, we catch errors thrown by the ComponentThatMightThrowAnError by using the new ErrorBoundary component. This way, if an error happens, the app won't crash and we can show the user a helpful error message.

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Improved Server-Side Rendering

Server-Side Rendering (SSR) is one of the most important ways to improve the speed of web applications. With React 18, SSR has been improved, which makes it possible for components to be rendered faster and more efficiently on the server. This makes it faster for pages to load and easier for people to use.

For example, let's say you have a web application that needs to load quickly and give users a smooth experience. With improved SSR, you can render your UI components on the server and send them to the client instead of rendering everything on the client. This can cut down on the time it takes for your app to load and make the whole experience better for the user.

function App() {
  const [data, setData] = useState(null);
  const [error, setError] = useState(null);

  useEffect(() => {
    fetchData().then((response) => setData(response)).catch((err) => setError(err));
  }, []);

  return (
    <div>
      <Header />
      {data ? (
        <React.Suspense fallback={<Spinner />}>
          <DashboardChart data={data} />
          <DashboardTable data={data} />
        </React.Suspense>
      ) : (
        error ? <ErrorMessage error={error} /> : <Spinner />
      )}
    </div>
  );
}

const html = renderToString(<App />);

console.log(html);

In this example, we use renderToString to render the App component on the server. So, we can make HTML that can be sent to the client and shown right away, without waiting for the JavaScript to load and run. With React 18's new server components feature, we can also define logic and markup that only works on the server. This lets us optimize server rendering even more.

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Conclusion

In conclusion, React 18 is an exciting new release with several improvements and new features that can help developers make better, faster, and more efficient apps. React 18 has a lot to offer, from better performance and handling of errors to a new JSX transform and better rendering on the server side. The automatic batching and concurrent rendering features are especially important because they can make it much easier to build complex apps that are more responsive and can grow as needed. With these new features, React developers can improve their apps and stay ahead of the competition. Overall, React 18 is a big step forward for the popular JavaScript library, and we can't wait to see what developers make with it.