What’s Coming in React 18? (Sneak Peek)

As we approach the release of React 18, there’s plenty of excitement surrounding the new features that promise to make React applications even faster, more efficient, and smoother to use. With Concurrent Rendering and Automatic Batching leading the way, React 18 introduces improvements that developers have been eagerly anticipating. Let’s take a sneak peek at the upcoming features, and see how they’ll impact the future of React apps.

1. Automatic Batching

One of the most anticipated features of React 18 is Automatic Batching. In previous versions, React would batch updates from event handlers or state changes that occurred within the same render cycle. However, it didn’t handle updates triggered by asynchronous code (like setTimeoutfetch, or Promises) in the same way. As a result, multiple state updates could trigger multiple renders, which was inefficient.

With Automatic Batching in React 18, React will now batch all updates together—whether they come from user interactions, async events, or anything else. This leads to fewer re-renders, and ultimately improves performance in your application.

How this impacts your app:
If you have an app that makes frequent async calls or uses Promises heavily, Automatic Batching will significantly reduce unnecessary renders. It’ll save you time optimizing your components and will allow React to handle performance for you.

Example:

// In React 18, this will trigger a single render:
fetchData().then(() => {
  setState1(data1);
  setState2(data2);
});

Previously, the two setState calls could have triggered separate renders. Now, React batches them together.


2. Concurrent Rendering

Concurrent Rendering is a set of powerful new capabilities in React 18 that will make React apps more responsive. It introduces the ability to pause and resume rendering work, enabling the browser to stay responsive even during complex updates.

What’s new in Concurrent Rendering?

  • React will now be able to pause rendering work, allowing it to prioritize important updates first.
  • It helps keep the UI interactive and smooth, especially during heavy rendering tasks like loading large data sets or complex animations.
  • You can now enable Concurrent Mode at the root of your app, which unlocks this behavior across your components.

How this impacts your app:
With Concurrent Rendering, your React app will feel snappier and more responsive, even with heavy rendering. You’ll be able to optimize the user experience by allowing React to work in the background without blocking interactions.

Example:

import { startTransition } from 'react';

startTransition(() => {
  // Your heavy, non-urgent update
  setSomeState(largeData);
});

By wrapping updates in startTransition(), React knows that these updates aren’t as urgent, allowing it to prioritize other interactive tasks like user clicks or typing.


3. useTransition Hook

The useTransition hook is another fantastic addition to React 18, aimed at improving the user experience during non-urgent updates. This hook allows you to manage “transitions” — updates that can be deferred without blocking interactions.

What does useTransition do?

  • It lets you mark certain updates as low priority so that they don’t interrupt important interactions.
  • React will be able to keep the UI responsive by working on these transitions in the background.

With useTransition, developers can now specify which parts of their UI can be delayed (like non-urgent data fetching or animations) and which need to be prioritized (like user interactions).

How this impacts your app:
useTransition will help keep the user interface smooth and prevent UI freezes by allowing time-consuming operations to run without interrupting immediate actions (like typing or clicking).

Example:

const [isPending, startTransition] = useTransition();

const handleChange = (e) => {
  startTransition(() => {
    setSearchQuery(e.target.value); // This update can be deferred
  });
};

Here, the search query is updated in the background without blocking the user from interacting with the page.


4. How These Changes Will Impact React Apps

React 18 brings a host of new features that’ll provide developers with more control over performance optimizations. These changes are especially beneficial for larger applications where multiple updates occur at once, leading to heavy re-renders.

The key takeaways are:

  • Automatic Batching will reduce unnecessary renders and improve performance.
  • Concurrent Rendering will make apps feel more responsive, even during complex updates.
  • useTransition will give you more fine-grained control over when to prioritize user interactions versus background updates.

These features provide new ways to optimize your app for performance, while keeping the development experience smooth and easy to manage. As React 18 rolls out, developers will be able to embrace these tools to create faster and more user-friendly applications.


Conclusion

React 18 is shaping up to be a monumental release that will significantly improve the performance and user experience of React apps. From Automatic Batching to Concurrent Rendering and the new useTransition hook, these features are set to change the way developers approach React app performance optimization.

While these features are still being finalized, their impact will be felt across the entire React ecosystem. Keep an eye out for the official React 18 release, and start preparing your apps to take full advantage of these exciting changes!

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