Understanding useDeferredValue in React 18: Enhancing Performance with Deferred State Updates

As React developers, optimizing the performance of our applications is always a priority. One powerful tool for achieving this is the useDeferredValue hook introduced in React 18. This hook helps keep our user interfaces responsive by deferring less important state updates, making it especially useful during intensive computations or frequent re-renders.

In this blog post, we’ll dive into how useDeferredValue works and how to use it to enhance performance in your React applications.

What is useDeferredValue?

The useDeferredValue hook allows you to defer updates to a state value until more urgent updates have been processed. This helps in scenarios where immediate updates could lead to performance issues, ensuring that the UI remains responsive even during heavy computations.

How useDeferredValue Works

• Purpose: It defers the value of a state, allowing React to prioritize more urgent updates first.
• Scenario: Useful in cases like intensive computations or rendering large lists, where immediate state updates can degrade performance.

Example: Implementing useDeferredValue

Let’s consider an example where we have a search input field. As the user types, the search results are updated. Without deferring the updates, each keystroke could trigger a costly search operation, potentially making the interface laggy.

Breaking Down the Example

1. State Declaration:

• query: Holds the current value of the input field.
• deferredQuery: A deferred version of query, updated less urgently.

2. useDeferredValue:

• Takes query as an argument and returns deferredQuery. The value of deferredQuery is deferred until the more urgent updates (like updating the input field) are processed.

3 . useMemo:

• Memoizes the filtered data based on deferredQuery and data, preventing unnecessary computations on every render.

4. Input Field:

• Updates query immediately as the user types.

5. Filtered Data:

The list is filtered based on deferredQuery, which updates less frequently than query, thus reducing the number of expensive computations and improving performance.

By using useDeferredValue, the search operation is deferred, making the typing experience smoother for the user, especially with large datasets or expensive computations.

In conclusion, useDeferredValue is a powerful addition to React 18 that can significantly improve the performance and responsiveness of your applications. By deferring less critical state updates, you ensure that your UI remains smooth and responsive, even during complex operations.