A Complete Guide to React 18's Newest Features

Ian Deed
Ian Deed
Published: 16.09.2022

The latest version of Facebook's technology framework, React 18, was released to developers in march this year. This release has focused on bringing performance improvements and upgrades to the platform's rendering engine to create a robust foundation for future features and functionality.

With a broad set of out-of-the-box improvements for teams, this release is proving to be more exciting than most in providing developers with a sneak peek at what's to come in the future of the React Framework. Amongst our top React Development companies the latest features and upgrade to come to React 18 today are already been put into practice in the apps and services they are creating for clients.

Here, we take a close look at each of the major features to appear in React 18. Breaking down what each one can do today and how you can use them in your future applications, we take a look at what recent changes to the technology will mean for React 19 and beyond.

React 18 Features and Changes

A small fragment of React 18 code shown on a dark IDE terminal

 

Starting with the fundamental changes coming to React 18, we break down what these changes mean for your teams, how to implement them within your apps, and the new features that they enable in the latest version of the framework.

For a complete analysis of the React framework before its most recent changes, you should take a look at our guide on the pros and cons of ReactJS development to analyze the advantages of Facebook's flagship framework.

Concurrent Rendering

The largest and most impactful change to come with the launch of React 18 is something that's happening behind the scenes. The framework's new concurrent renderer unlocks powerful new capabilities for developers to deploy.

Within this release, concurrent UI rendering is invoked at the developer level when used with one of the latest features and tools included with React 18. In the future, however, this is likely to change as existing libraries and tools are built or upgraded with concurrency in mind. In the next few years, concurrent UI rendering in React will have an extraordinary effect on the performance and usability of applications.

The shift to a new type of UI rendering is a significant change to the way React works for developers. Previous versions of the framework have used uninterruptible transactions that were unchangeable in progress. The latest version of React's tooling introduces UI updates that can be paused, re-started, or even abandoned in progress.

Yet, despite these changes, React aims to guarantee UI consistency regardless of the rendering state happening in the background. While the changes this makes to React's UI are significant, complex, and difficult to get a handle on — it provides React's renderer the opportunity to work on multiple tasks in the background without blocking the main thread.

For developers, effective concurrency models will enable fast and responsive UI with complex interactions taking place under the surface.

This change is the most significant in React 18 and one that will define changes happening to the framework for several versions to come. Future versions of React intend to build on this feature set and take full advantage of the capabilities it unlocks.

For organizations, recent upgrades to React mean that now is a great time to hire react developers to build, improve, and upgrade your applications using the best available tooling.

For developers updating their applications to React 18, this change shouldn't have any effect on existing functionality. Despite fundamentally changing how rendering takes place, these changes are only enabled for application features released within React 18 and beyond.

Gradually, it's expected that more and more libraries will become concurrency compatible and enable developers to deploy the tooling into end-user applications.

Our ultimate guide to ReactJS can help you get to grips with React from its most basic concepts through to deploying the framework to build your apps with the latest tools and technologies included in this year's release.

Data Suspense

The latest version of React introduces additions to data suspense that allow data fetching to be prioritized for opinionated frameworks. Data suspense allows React apps to delay loading on components that are known to be slow, specify a loading state for the UI, and allow pages to be rendered at a pace that isn't dictated by their slowest components.

Suspense isn't entirely new to react but its latest update has added additional capabilities to the feature and made use of concurrent rendering to improve its tooling.

Automatic Batching

One of the key new features to come to React 18 is an automatic batching tool aimed at improving overall application performance. The key advantage of this tool for developers comes in reducing the number of re-renders required as state changes happen within the app.

In previous versions of React, state changes taking place outside event handlers couldn't be batched together into a single UI transaction. This often resulted in network calls creating multiple needless re-renders at a high-performance cost.

With React 18, automatic batching allows for all updates to state to be batched together whether they take place in event handlers, timeouts, or callbacks. For app developers, this is a tool that will greatly reduce the amount of work being done in the background.

Transitions

Another entirely new feature to come to React, transitions allow developers to split UI updates into urgent and non-urgent categories.

Urgent updates, the default category for all UI transactions, are interactions and changes where the user would expect immediate and direct feedback as the result of an action. Clicks, swipes, typing, and button presses are all examples of urgent updates that would feel strange to the user if audible, haptic, or visual feedback was somehow delayed or missing. In contrast, switching between UI views might be labeled as non-urgent by the developer to allow for interruptions to take place due to a button press or network update.

The response to a user clicking on a search field, for example, should be an urgent UI task. The results returned from that search, however, could be populated as they come in or all at once—creating an opportunity to use a non-urgent update in React 18.

Updates marked as non-urgent transitions allow for the update process to be paused or abandoned as other UI changes take priority. These transitions are one of the key new use of concurrent rendering in React 18.

New Client and Server Rendering APIs

React 18 has made some recent changes to the APIs exposed for client and server-side rendering. This change allows developers to use the existing API in the same way and introduces an opportunity for a more gradual stage-by-stage transition into React 18.

New APIs exposed from the React DOM Client:

  • createRoot: used instead of ReactDOM.render, creates a root to render or unmount
  • hydrateRoot: Used instead if ReactDOM.hydrate, hydrates a server-rendered application

Both of these APIs are essential to working with the latest versions of React 18. The full documentation for React DOM can be found here.

Similarly, two new APIs from the React DOM Server are:

  • renderToPipeableStream: for streaming in Node environments
  • renderToReadableStream: for modern edge runtime environments, such as Deno and Cloudflare workers

Full documentation for the React DOM server is available here.

New Strict Mode Behaviours

Some of the changes taking place to improve React applications in the future are being implemented today into the debugging behavior of the application. Writing applications in strict mode will simulate unmounting and re-mounting components to prepare developers for upcoming changes to the way components are handled in the future.

Ideally, all components should handle this simulated behavior without flaws or errors by preserving the state as components are unmounted and remounted. You can find the documentation for ensuring this feature works as expected here.

Two software engineers working on code at a shared laptop in an office setting

New Hooks

New hooks added to React 18 this year include:

  • useID. A new hook for generating uniqueIDs on the client and server for integrating component libraries with accessibility APIs
  • useTransition. Used in conjunction with startTransition to allow developers to mark state updates as non-urgent
  • useDefferedValue. Allows developers to defer re-rendering a non-critical part of the component tree
  • useSyncExternalStore. Allows for external stores to support concurrent reading—now the recommended solution is to integrate a library with state external to React
  • useInsertionEffect. Allows CSS in JavaScript libraries to address some performance issues. This is provided to fix legacy issues rather than for implementation in a new use case

Upcoming Feature: Server Components

Upcoming versions of React are intended to take full advantage of concurrency behind the scenes. Server components are one example of these features currently in development that will allow developers to build apps that effectively span both client and server-side development.

An initial version of server components is expected in a minor release of React 18 in the coming months.

Preparing for Change

The groundbreaking changes taking place in React 18 aren't just its new features in isolation, though these are impressive, but the applications and possibilities that they enable in the future.

Upcoming react applications will richly benefit from built-in concurrency in its libraries, the ability to pause components and reload state seamlessly, and the capability to span both client and server-side development for both rich user interactions and server-side rendering performance.

Upgrading from previous versions of React should be straightforward and unlikely to introduce any app-breaking features. The features and benefits it unlocks make it well worth the couple of hours it should take to implement. Set up a strong foundation for the future of your apps today and give it a go.

FAQs:

Q1. How do I switch from React 18 to 17?

Downgrading from React 18 to React 17 should be a relatively straightforward process. Using NPM you can simply remove the latest version of the framework using:

  • npm uninstall react

This will remove react from your current system. You can then install version 17 of React using:

  • npm install react@17.0.0

This will install react version 17 and leave the latest version for a future upgrade. You can safely elect not to take this upgrade and use React with version 17 as long as you like. If you plan to upgrade again in the future you can freely skip over any intermediate versions and use npm to install the latest version of the framework automatically simply by using:

  • npm install react

Q2. Is React 18 backward compatible?

Yes, React 18 is fully backward compatible with previous versions of the code. Despite offering some significant new features to the way UI updates are rendered and processed, these new changes to the framework are entirely avoided unless using React 18-specific features and upgrades.

For developers looking to experiment with React's latest concurrency features, they can be implemented piecemeal into applications with remarkable safety and assurances that the remainder of the application won't be adversely affected.

Future versions of React are expected to build on the concurrency changes and updates being brought in through React 18. For developers, this means that the latest version of React is a great place to start with building the fundamentals of long-lasting applications that will take advantage of performance and stability features coming in the next few months and years. React 18 is a great place to start when experimenting with new tools to improve application performance and implement new feature sets.

Q3. Is React 18 stable?

Yes, React 18 is in stable release. This means current React apps are continuously being updated and upgraded to use the APIs and tools included in React 18 without app-breaking issues. This is particularly remarkable in the case of React 18 as the update introduces a fundamental change to the way the framework renders UI components.

Concurrent rendering, introduced in React 18, is one of the biggest changes the framework has seen in some time. Yet, it's a feature set that manages to be applied only to services and calls that use it with the framework's newly released libraries and tools and not those from legacy applications. This means apps upgrading to React 18 but not taking advantage of concurrency won't experience any side effects or changes resulting from the shift. Developers looking to experiment with the latest concurrency features can do so with the freedom from introducing side effects elsewhere in their applications.

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