New Features in React 18 that You Have to Know About

React v18.0, the most recent version, was published in March 2022. It comes with a tonne of intriguing new features. As a leading ReactJS development company, our team is excited with this update. There is often controversy surrounding new React versions, and this one is no different. However, this version has proved to be rather big in out-of-the-box ideas in terms of features. The top frontend library is admired for its ongoing commitment to improving and innovating. React 18 does not disappoint us on that ground. Also, the primary focus of React, as always has been, is improving performance. The biggest new features introduced in React 18 tend to show high focus performance enhancement. In particular, the rendering engine has been updated with a lot of priority.

Let’s get right to the details of all the new features in React version 18.0 without any more introduction.

What has React 18 added?

Based on the new capabilities and general enhancements to rendering models, React 18 has a tonne of new upgrades. React Labs has been working on some revolutionary changes to the library. Owing t this, React v18.0 has some of the most intriguing new features.

Of these, the most thrilling are Concurrent React and Suspense. We would go into great depth on both of these things. To begin with, the most significant enhancements in this edition are Automatic Batching and Transitions. Additionally, Suspense and Concurrent both received some integration enhancements. For ease of adoption, several additional hooks have also been introduced.

In this section, even though it is still under construction, we will also talk about server components. To facilitate its wider adoption, it is undergoing minor adjustments. React 18 has prioritized 3rd party users and smooth adoption of this version rather highly. We would see several proofs of this, like the hooks, I briefly mentioned above, as we navigate through the different features introduced in this version.

Concurrent React

Let us first understand concurrency. What is concurrency in terms of programming? The ability to run multiple programs or multiple parts of a program simultaneously is known as concurrency.

Concurrent React, a new feature of React version 18.0, seeks to drastically change the way we handle concurrency.

Concurrent React is not just an update, says the React Team. They are referring to it, and quite rightly so, as an “implementation detail” that provides room for more recent changes. You are probably not overly concerned with implementation specifics as a frontend developer. You are more likely to care more about “what” enters your UI than “how.” In this sense, Concurrent React is nothing short of a foundational upgrade to the main rendering paradigm of React, therefore it is still pertinent to discuss here.

Concurrent React Advantages

How does Concurrent React make our applications better? Concurrent React’s main feature is that it enables rendering to be interruptible. We habitually associate interruption to be a bad thing, but here, it adds a major utility. Being interruptible suggests that now React can start, halt, and resume while rendering an update. It may even decide not to continue working on a render that is already in operation. How does this help? This enables React to guarantee that the user interface will remain to appear consistent even if a render stops. In other words, Concurrent React improves our applications by giving React the capacity to prioritize components. Let us talk about this in a little more depth.

This is achieved by postponing DOM updates until after a full tree assessment. As a result, React is now able to construct new screens in the background without causing the main thread to pause. By enabling it to respond to human input even as it is performing a rendering operation, it enhances the user interface. Reusing the previous state while using concurrent React also enables removing UI elements from the display and adding them later.

As I already mentioned, we are going to see efforts made to make the adoption of React 18 painless, in nearly all new updates of React 18. For React Concurrent too, the main emphasis right now is on a gentle transition of more traditional react capabilities to integrate with concurrent. We have adequate room to gradually use Concurrent in our programs. You can selectively enable Concurrent on some parts of your program by using <StrictMode>.

Suspense

Suspense is a highly anticipated feature that finally got added to React in React 18. Previous versions of React have had minor segments of the Suspense feature as the React Lab wanted to try it out at a smaller scale before releasing it as a comprehensive feature. More updates will be added to Suspense in future minor version upgrades of React 18.

What does Suspense do? With React v18.0, Suspense may fetch data in opinionated frameworks such as Next.js Relay, Remix, or Hydrogen. Important to note here, that even if it is technically possible, it is not advised to employ Suspense for global data-fetching. The reason why Suspense has been highly awaited is that fetching data from other libraries and frameworks is highly necessary for building a good application. It allows developers a great amount of freedom and flexibility. Suspense makes the task of importing from other frameworks easy. It’s no wonder that we are so excited about Suspense!

More primitives that would make it easier to get to your information without an opinionated framework are expected to be included in the next ReactJS versions. When linked with your code’s primary structure, suspense works nicely. Particularly, the rendering environments on your data layer, router, and server. We can therefore anticipate that other frameworks will continue to be crucial parts of the React workspace in the long run. This, as you can guess, would ultimately improve the utility and flexible nature of React itself.

There is more to Suspense than data-fetching. With React.lazy, suspense can also be used for code splitting on older React versions. Yes, you guessed it correctly, this helps in the adoption of React 18. The objective is to expand Suspense to manage all asynchronous tasks, such as downloading data, code, and graphics.

Server Components

Server Components have not yet been introduced, as I previously stated. Then why are we talking about it here if it is not available in React 18? Because it will be made available very soon as a React 18 subversion, perhaps 18.1 itself. Server components are expected to revolutionize server engine rendering, and honestly, we cannot keep calm.

What would Server Components do? Developers would be able to construct programs that function on both the server and the client thanks to server components.

How does it accomplish that? Server Components can combine traditional server rendering’s increased efficiency with the robust interaction of client-side apps. Additionally, we may anticipate good compatibility between server components and concurrent features like streaming server rendering.

Automatic Batching

Batching is by itself a rather important functionality of React. To improve the code’s performance, React uses batching. Need to know what batching is? Well, in React event handlers, batching is the process of combining many state updates into a single re-render. The new automatic batching update in React 18 performs, as the name suggests, automatic batching. It is now possible to automatically batch event changes within setTimeout, promises, and native event handles.

Transitions

This feature is humongous in terms of improving the rendering of UIs. Let us get straight into understanding what the Transition feature does and how it can make our lives easier.

Updates come in two forms: urgent and non-urgent, as we all understand. Direct user-UI interaction necessitates urgent updates. Meanwhile, tasks like changing UI views form non-urgent upgrades.

Transitions alter the way non-urgent updates are managed by React. Non-urgent updates are handled at transitions using the newly added Transitions feature in React 18. These are presented in a fragmented way. Ultimately, it helps in managing urgent and no-urgent updates in a more seamless manner to provide our UIs with a higher responsivity. However, it is important that we differentiate non-urgent updates from urgent updates in our codes. React 18 has hooks to achieve this. Let us see how.

In order to distinguish between urgent and non-urgent updates, we can use the startTransition API. startTransition updates would be treated as non-urgent by React. When an important update arrives, it will pause these updates. React would discard earlier renders and only display the most recent update in response to such disruptions.

It is quite clear at this point, that much like the other features, Transitions was also introduced keeping in mind an easier adoption of the feature. For this reason, two hooks are available for transitions:

Transition Hooks

• useTransition: for transitions that are just begun, including for values that keep track of pending states.
• startTransition: When the useTransition hook is not available, we are supposed to use startTransition to initiate transitions.

It is probably important to note here that the new features of React 18 are inter-dependent at several points. For example, in the case of Transitions, Concurrent rendering makes transitions possible since it allows for updates to be interrupted. The user would get the most recent content in the event that an update was re-suspended. In the background, Transition would perform the transition update.

We will see more such interdependencies when we discuss the other new hooks introduced in React 18.

New Features with Suspense

The React server now supports Suspense and has more capabilities thanks to concurrent rendering capabilities. Suspense enables you to declaratively specify the loading status for a component tree segment if it is not yet ready to be rendered. The “UI loading state” becomes a declarative concept out of the box in the React programming model because of Suspense. We may anticipate building more sophisticated utilities on top of it.

Please note that in React 18, Suspense must be used in tandem with the transition API. If you interrupt React during a transition, it would not be replacing rendered data with fallback content. It will instead defer rendering until enough data has loaded. By doing so, a bad loading state would be avoided.

Redesigned Client and Server Rendering APIs

Improving the client-server rendering APIs for enhanced rendering engines and thereby, better responsiveness of applications built on React has been highlighted as a major focus by the React Team in several media so far. In React 18, they have delivered well on this promise. React 18 works with several client-server rendering APIs that have been exported and recreated especially to work with React 18. These also help in allowing a smoother transition to React 18 from older versions. Thus, the adaptability factor of the new update has been prioritized here as well.

DOM Client

React 18 exports the createRoot and hydrateRoot APIs from react-dom/client. If these are not used, React 18’s new features are likely to not function. These two APIs both support onRecoverableError. This new feature alerts developers when React fixes any errors that may have occurred while rendering or monitoring hydration. React would by default use console.error and reportError in earlier browsers.

• createRoot: ReactDOM.render is replaced with createRoot. Unmount or render a new root via rendering.
• hydrateRoot: ReactDOM.hydrate has been replaced with hydrateRoot. Using the new DOM Server APIs, hydrate server-rendered apps.

DOM Server

For DOM Servers, on the basis of the react-dom/current server’s APIs, new APIs were created. On the server side, they support suspense. With these now available to React, even though renderToString is still functional in React 18, it is best to avoid using it.

• renderToPipeableStream: In Node environments, this enables streams to be rendered to pipeable streams.
• renderToReadableStream: In contemporary edge runtime environments like Cloudflare workers and Deno, this allows streams to be rendered to read-only streams.

Strict Mode in React 18

React is currently working on adding the ability to add and delete UI elements while retaining the state. The preceding screen must be instantly visible in React. Let’s take the case of a user who toggles between displays. To accomplish this, React can unmount as well as remount trees while continuing to use the component state. Using this functionality, React apps will operate more quickly. Components must, however, be resistant to recurrent mounting and deletion of effects. The majority of effects will work as planned. Others might think they might have been mounted or destroyed before.

To help find these issues, React 18 updates Strict Mode with a new development-only test. This new check will automatically unmount or remount all components after they mount for the initial time, restoring the past state on the subsequent mount.

Whenever a component is in development mode, the Strict Mode simulates unmounting or remounting the component.

New Hooks

Hooks in React are terribly important for developers and the process of efficient development. Small recap on what are hooks in React. Hooks are ready-made components that we can pull from the React library and use throughout our codes. Besides being readily available, they eliminate the necessity to rewrite components multiple times while building an application. Hooks are clearly distinguishable from their “use-” prefix.

Naturally, React 18, like any major version upgrade, had to come up with some new hooks to ensure that all new features function seamlessly. The new hooks also help in increasing the adaptability of React 18. Let us go through the major new hooks in React 18 sequentially.

useID

Using useId, separate IDs are generated on the client and server, avoiding hydration discrepancies. When integrating component libraries to accessibility APIs that require unique IDs, is most useful. React 18’s new streaming server renderer broadcasts HTML out-of-order, which fixes a problem with prior versions of the framework like React 17 and 16. The fact that useId does not provide keys in a list may be pertinent to mention at this point. Your data must produce the keys.

useTransition

As was previously mentioned, the useTransition and startTransition hooks allow you to identify which state updates are not urgent. Other state updates are automatically labeled urgent when a state update is categorized as non-urgent. React pauses less urgent state updates to make room for more urgent ones. Again, as already mentioned, these hooks are interdependent with Concurrent Rendering.

useDeferredValue

With the useDeferredValue hook, you can delay re-rendering any non-urgent component of the tree. Although similar to debouncing, there are some key differences between the two. React will attempt the delayed render as soon as the initial render appears on the screen because there is no predetermined amount of time for the delay. Deferred renderings are interruptible and don’t block user input.

useSyncExternalStore

UseSyncExternalStore is a new hook that simultaneously modifies external storage. They can manage concurrent rendering because of this. Any library interacting with a state outside of React should utilize it. It does away with the useEffect rule when creating subscriptions to outside data sources.

useInsertionEffect

By utilizing the new hook useInsertionEffect, the CSS-in-JS libraries can address rendering performance issues. This is something you won’t likely need until you’ve already built a CSS-in-JS library. This hook will run after a DOM modification, but before the updated layout is read by the layout engine. This resolves an issue with React version 17.0. But in React v18.0, it is even more important. In order to allow time for the layout to reload during concurrent rendering, React 18 concedes to the browser.

To wrap this up, what should we look forward to from React?

This conversation is almost reaching its conclusion. There have been various rumors regarding what would happen ever since React 18’s debut in 2021 was announced. We planned for the upcoming React version to concentrate on maintaining third-party libraries. This was mostly accurate, as we can now see. Although React 18 is filled with new capabilities, progressive change is given a lot of attention.

One of the most intriguing elements for improving performance is concurrent React. In earlier iterations of React, Suspense was present initially. The capabilities of React 18 have been extended to their fullest potential. Suspense gives the way for innovation while Concurrent guarantees performance. Suspense definitely incurs some major promises in terms of innovation in the future of the React ecosystem.

React 18 has handled adoption-related worries nicely. To make sure that the new features of React 18 work for the maintainers of third-party libraries, it has added a number of new hooks. Also incorporated are new client and server rendering APIs. These are essentially updated exports from earlier APIs. This, too, makes it possible to adopt React 18 gradually and without fuss.

A few even more thrilling sneak peeks at upcoming React versions can be found in the React Team’s most recent statements. React Server Components are the first to be released. Additionally, we are learning about the benefits of transition tracing, SSR optimization, and asset loading. The React Optimizing Compiler announced at React Conf 2021, is also in progress!

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