The useDeferredValue hook - React 17.0 beta features

Introduction to the useDeferredValue Hook

React's useDeferredValue hook is a new feature that was introduced in React 17.0 as a beta release. It allows a developer to specify a value that should be used with a delay, allowing for the possibility of rendering an intermediate state while waiting for the deferred value to resolve. This can be useful in situations where you want to optimize the perceived performance of a component by rendering content as quickly as possible, even if it is not the most up-to-date.

When to Use useDeferredValue

One common use case for useDeferredValue is when you have a slow-loading prop that is passed to a component, but you don't want to block rendering of the rest of the component while waiting for the prop to resolve. Instead, you can use a placeholder value or an intermediate state while waiting for the prop to resolve.

Another use case is when you have a value that is updated frequently, but the updates are not critical to the user experience. In this case, you can use useDeferredValue to only update the value after a certain delay, allowing for a smoother experience for the user.

How to Use useDeferredValue

Using useDeferredValue is similar to using other React hooks. First, you need to import the hook from the react package:

import { useDeferredValue } from 'react';

Next, you can call the hook within a functional component and pass it two arguments: the value you want to defer, and the delay time in milliseconds. The hook will return the deferred value, which you can then use in the component like any other value:

const MyComponent = ({ slowLoadingProp }) => {
  const deferredProp = useDeferredValue(slowLoadingProp, 500);

  return (
    <div>
      {deferredProp}
    </div>
  );
};

In the example above, the component will render with the placeholder value of slowLoadingProp for at least 500 milliseconds before updating with the actual value.

It's important to note that useDeferredValue only delays the rendering of the value, not the resolution of the value itself. This means that if the value takes longer than the specified delay to resolve, it will still be displayed as soon as it is available.

Conclusion

The useDeferredValue hook is a useful tool for optimizing the perceived performance of a React component by allowing for the rendering of intermediate states or placeholder values while waiting for slow-loading or frequently updated values to resolve. It is easy to use and can greatly improve the user experience of your application.