React 19 is here, bringing a wave of enhancements designed to make building web applications smoother and more efficient. From improved data handling to faster loading times, this update empowers developers with several exciting features. Let’s dive into what’s new and see them in action:
1. Actions: Simplifying Data Mutations (Example: Optimistic Updates)
One of the most significant additions in React 19 is the Actions API. It tackles a common challenge: managing data mutations and state updates. Previously, developers had to write code to handle pending states, errors, optimistic updates, and sequential requests. Actions eliminates this boilerplate code, streamlining the process.
Here’s an example: Imagine a form where a user updates their profile picture. Traditionally, you’d need to manage a loading state and potentially revert changes if the upload fails. With Actions, you can leverage the useActionState hook:
function ProfilePictureForm() {
const [picture, setPicture] = useState(null);
const { state, action } = useActionState(async () => {
const formData = new FormData();
formData.append(‘picture‘, picture);
const response = await fetch(‘/api/upload-profile-picture‘, {
method: ‘POST‘,
body: formData,
});
return await response.json();
});
const handleUpload = async (event) => {
setPicture(event.target.files[0]);
await action(); // Trigger the action to upload the picture
};
if (state.isLoading) {
return <p>Uploading…</p>;
}
if (state.error) {
return <p>Error: {state.error.message}</p>;
}
// Display the uploaded picture or a placeholder if no picture is selected
return (
<div>
<input type=“file“ onChange={handleUpload} />
{picture && <img src={URL.createObjectURL(picture)} alt=“Profile Picture“ />}
</div>
);
}
In this example, useActionState manages the asynchronous upload process, including the loading state and potential errors. The component simply triggers the action (action()) when the user selects a picture, and useActionState handles the rest.
2. Smoother Asset Loading and Rendering (Example: Preloading Fonts)
React 19 prioritizes a seamless user experience by introducing features that optimize asset loading. It introduces lifecycle Suspense for assets, enabling React to determine when content like fonts are ready for display. This eliminates the issue of “unstyled” flickering that can occur during initial rendering.
Additionally, React 19 offers new Resource Loading APIs like preload. Here’s an example of preloading a custom font:
function App() {
React.preload(‘/fonts/my-custom-font.woff2‘); // Preload the font in the background
return (
<h1 style={{ fontFamily: ‘MyCustomFont‘ }}>Hello, World!</h1>
);
}
By preloading the font, React ensures it’s available before rendering the heading, resulting in a smoother visual experience.
3. Experimental Features with Promise (Example: use Hook)
React 19 introduces an experimental API called use. This hook allows developers to directly read the value of resources like Promises or context within the render function. Here’s a basic example (note that this is still experimental):
function MyComponent() {
const [data, setData] = useState(null);
const fetchData = async () => {
const response = await fetch(‘/api/data‘);
setData(await response.json());
};
useEffect(() => {
fetchData();
}, []);
const formattedData = use(data?.map(item => item.name)); // Access data from the promise
return (
<div>
{formattedData?.length > 0 ? (
<ul>
{formattedData.map(name => (
<li key={name}>{name}</li>
))}
</ul>
) : (
<p>Loading…</p>
)}
</div>
);
}
In this example, the use hook retrieves the data from the promise within the render function, allowing for more concise code. Remember, this feature
Follow me on : Github Linkedin
