Optimizing suspense for slow network connections in React

16 Oct 2023

In recent years, React has introduced new features like Suspense and React.lazy to handle code splitting and improve performance by loading components only when they are needed. However, when dealing with slow network connections, these features might not work as effectively as expected. In this article, we will explore some techniques to optimize Suspense for slow network connections in React.

Understanding Suspense and React.lazy

Before diving into optimizations, let’s briefly understand Suspense and React.lazy.

Suspense is a React component that allows you to suspend rendering while waiting for some asynchronous data to load, such as data from an API or lazy-loaded components. It provides a fallback UI, which can be shown until the data is loaded and ready to be displayed.

React.lazy is a function that allows you to dynamically import components using lazy loading. It allows splitting your code into smaller chunks that can be loaded on demand, improving the initial load time of your application.

Optimizing Suspense for Slow Network Connections

Delay displaying the fallback UI: By default, Suspense shows the fallback UI as soon as any of its child components are being fetched. However, in the case of a slow network connection, it might lead to a flickering effect, as the fallback UI can be shown and hidden multiple times. To avoid this, you can delay displaying the fallback UI by setting a timeout, and only show it if the data takes longer than the timeout threshold to load.

Example code:

const TIMEOUT_THRESHOLD = 3000; // 3 seconds

function MyComponent() {
  return (
    <Suspense fallback={null}>
      <DelayFallbackUI timeout={TIMEOUT_THRESHOLD}>
        <LazyLoadedComponent />
      </DelayFallbackUI>
    </Suspense>
  );
}

function DelayFallbackUI({ timeout, children }) {
  const [showFallback, setShowFallback] = useState(false);

  useEffect(() => {
    const timeoutId = setTimeout(() => {
      setShowFallback(true);
    }, timeout);

    return () => {
      clearTimeout(timeoutId);
    };
  }, [timeout]);

  return showFallback ? <FallbackUI /> : children;
}

Implementing a network status indicator: Instead of showing a static fallback UI, you can provide a more informative user experience by implementing a network status indicator. This indicator can display the actual progress of the data loading process, giving users an idea of how long they need to wait.

Example code:
```
function NetworkStatusIndicator() {
  const { status } = useNetworkStatus();

  return (
    <div>
      {status === "loading" && <Loader />}
      {status === "error" && <ErrorUI />}
    </div>
  );
}

function MyComponent() {
  return (
    <Suspense fallback={<NetworkStatusIndicator />}>
      <LazyLoadedComponent />
    </Suspense>
  );
}
```
In this example, the useNetworkStatus hook can be implemented to keep track of the loading status, such as “loading”, “error”, or “success”.

Prioritizing the loading of critical components: If your application has critical components that need to be prioritized, you can use the PriorityLevel API provided by React in order to control the order of resource loading. By defining different priority levels for components, you can ensure that critical components are loaded first, even if they are located deeper in the component tree.

Example code:

const { startTransition } = React.useTransition({
  timeoutMs: 2000,
});

function MyComponent() {
  return (
    <div>
      {/* Critical component */}
      <PriorityLevel level={1}>
        <Suspense fallback={<FallbackUI />}>
          <CriticalComponent />
        </Suspense>
      </PriorityLevel>

      {/* Non-critical component */}
      <PriorityLevel level={0}>
        <Suspense fallback={null}>
          <LazyLoadedComponent />
        </Suspense>
      </PriorityLevel>
    </div>
  );
}

In this example, the CriticalComponent is wrapped in a PriorityLevel component with a higher level, ensuring that it is prioritized over the LazyLoadedComponent.

By implementing these optimizations, you can enhance the user experience in React applications, especially for users with slow network connections. Remember to always test and measure the impact of these optimizations on different devices and network conditions to ensure the best performance for your application.

That’s all for now! Hope you found these techniques helpful for optimizing Suspense for slow network connections in React.

Understanding Suspense and React.lazy

Optimizing Suspense for Slow Network Connections

References