React is on a never ending journey of enhancements. Have you experienced a new feature in React that doesn’t radically improve the developer experience, or the performance of an app, or ultimately an end-users experience? Two of the latest features, React Suspense and Concurrent Mode, are exciting efforts that will change the way we use React to render, to obtain data, and create interactive applications for end-users, which will help to meet their expectations in the online world we live in now.

What is React Suspense?

React Suspense is a new approach to managing asynchronous operations with your components. In the past, while fetching data or using a dynamic import to load code, the associated loading logic would be woven within your entire application. This approach increased both design complexity and removed a level of consistency when dealing with loading states across different parts of your application. In other words, it just moved state around without actually making it easier to manage. Utilizing the new Suspense API, components can now “wait” until all of the data or JavaScript code is available before it renders, which is drastically simplfying the overall approach and ensuring a better user experience with a more consistent UI.

Now, rather than parts of your UI flashing awkwardly while content is loading, for example, if you are showing user data in a Flexbox or limited view port and you are fetching that data asynchronously, where React is only rendering this one part of the UI only when the associated data is available, if you use Suspense to manage the state associated with fetching the user data, you can use placeholder UIs when specifying what it will load when the content is available. Placeholder UIs can be loaders or spinners or skeleton screens, for example.

While items that you fetch from the backend is likely what most developers will deal with, the use of Suspense also applies with code-splitting patterns too. For single page applications, when using a code-splitting pattern, you want to achieve the best user experience possible even when downloading JavaScript code is also part of the overall user experience. This is one feature that allows you to allow your app to download JS chunks when they are needed and not compromising the user experience.

What is Concurrent Mode?

Concurrent Mode is a new feature in React which changes how rendering works in React. In summary, React multitasks by preparing multiple UI versions simultaneously and decides what to update based on user actions.

This concurrency allows for React to pause and delay less important work, while React focuses on rendering things that need immediate response. For example, when the user initiates a long task (say, a heavy computation or network request), they can still freely interact with buttons, forms, or animations without any hiccups or lag.

Additionally, when in Concurrent mode, it will help make animations and transitions feel more fluid and natural by managing interruptions when rendering. Because of this fluid management, it allows applications to feel much less bulky and smoother in overall user experience.

How Suspense and Concurrent Mode Work Together

Suspense and Concurrent Mode are powerful companion technologies that offer new possibilities to React developers. Suspense is focused on handling waiting for asynchronous resources while Concurrent Mode runs concurrently with Suspense to make sure waiting does not freeze or block the UI.

As an example, if Suspense is able to delay rendering until the data loads, Concurrent Mode allows React to continue rendering other parts of the application, while keeping everything interactive and responsive. Together, you can enable more advanced user interface configurations like streaming server-side rendering, progressive hydration, and smooth transitions when going between a loading state and ready state.

Benefits of Using Suspense and Concurrent Mode

Improved User Experience: Showing meaningful loading states and keeping the UI responsive engages users and reduces frustration from wait times.

Better Performance: Concurrent rendering reduces unnecessary re-renders by prioritizing essential updates and it does not freeze the UI while waiting for updating tasks to finish.

Cleaner Codebase: Developers can express asynchronous logic more clearly and declaratively including included loadings states and error states instead of scattering them all over.

Future-Proofed Code: Together Suspense and Concurrent Mode will act as foundational features for future innovations from React, leaving your applications ready for progressive improvements, keeping up with the ever-changing front-end landscape.

Issues and Risks

Suspense and Concurrent Mode each hold promise, but there is a significant amount of work to be done. There are many popular third-party libraries that still need to adjust their libraries to support them and are behind. And using these features will change the approach developers have to rendering and data flow in React.

Learning how to make good use of Suspense and Concurrent Mode could be timely for everyone, especially teams used to conventional React usage. Testing is also likely not going to be as simple due to the asynchronous and concurrent nature of rendering.

But spending time on this early gives applications *real* longevity and an opportunity toward providing a competitive advantage by improving performance of user experience.

Real World Scenarios

Data-bound dashboards: Stay responsive with complex visualizations and data grids when loading entire data sets at once

Progressive web application: Occlude perceived performance until actual content loads, and place holders stream in content.

Interactive forms: Stay responsive through validation and submission of forms.

Code-splitting strategies: Only load feature specific javascript on demand, which means reducing page load times without reducing experience.

Conclusion

React Suspense and Concurrent Mode signify a significant shift in how frontend applications can manage rendering and async data. These features enable developers to build faster, more performant, and user-friendly apps that adapt seamlessly to changing network and device conditions.

Though these new features require some learning and consideration, the improvements in performance and user experience are significant. By choosing to adopt Suspense and Concurrent Mode today, you are enhancing your React applications for the future with, hopefully, new ways to create smooth, performant, and modern web experiences.

By utilizing these new capabilities, developers can gain a new level of control over when certain UIs may render, and ensure their apps remain competitive and enjoyable in an ever-expanding digital world.