Managing UI Updates Smoothly with useDeferredValue Hook in React

The art of managing user interfaces (UIs) involves dealing with a slew of data and changes in state. React, a popular JavaScript library for building UIs, provides several tools to help developers create smooth, user-friendly interfaces. One such tool is the useDeferredValue hook, a feature that allows developers to delay updates to a part of the UI, ensuring a smooth and responsive user experience.

What is useDeferredValue?

The useDeferredValue hook lets you control the timing of when parts of your UI get updated. You use this hook when you want a value to "lag behind" the latest state. For example, if you are fetching new data, you might want to display stale data until the fresh data is ready to be shown.

The structure for using the useDeferredValue hook is as follows:

Here, the "value" can be of any type - a primitive value like a string or number, or an object created outside of rendering.

During the initial render, the "deferredValue" returned will be the same as the "value" you provided. However, for updates, React will first attempt a re-render with the old value and then start a background re-render with the new value.

This hook can be used to show stale content while fresh content is loading, indicate that the content is stale, or defer re-rendering for a part of the UI.

Implementation of useDeferredValue

Let's consider a simple use case: a search page where a user types in a query, and search results are displayed as they are typed. Here's how you could use the useDeferredValue hook in this scenario:

In this setup, during the initial render, the deferredQuery will match the query provided. During updates, React will first re-render without updating the deferredQuery, then try to re-render with the updated value in the background.

This approach ensures a smooth transition between states by maintaining an older state while preparing to transition to a new one.

Caveats with useDeferredValue

While useDeferredValue is powerful, it's not without its caveats. The values you pass to this hook should either be primitive values or objects created outside of rendering. If you create a new object during rendering and pass it immediately to useDeferredValue, it may cause unnecessary background re-renders.

Moreover, it's important to note that useDeferredValue does not prevent extra network requests and doesn't cause any fixed delay. Any updates caused by events will interrupt the background re-render and get prioritized over it.

When to Use useDeferredValue?

You can use this hook when you want to defer the re-rendering of a part of the UI. For instance, if you have a component that re-renders slowly and you don't want it to block the rest of the UI, you can use useDeferredValue to prioritize other updates.

Comparing with Debouncing and Throttling

You might wonder how deferring value is different from common optimization techniques such as debouncing and throttling.

Debouncing waits for the user to stop typing before updating the UI, and throttling updates the UI at regular intervals. useDeferredValue, on the other hand, works at the rendering level. It doesn't require any fixed delay, and its behavior adapts to the user's device. If the device is fast, the deferred re-render will happen almost immediately, while on a slow device, the re-render will lag proportionally.

In conclusion, useDeferredValue is a powerful React hook that can help you optimize the performance of your application by managing updates to your UI in a more efficient and user-friendly way. It might be your go-to tool when handling large data changes or complex state transitions. Happy coding!