Very often you need some fields in your SPFx web parts. Like text fields, dropdowns, checkboxes, etc. While you can manually perform form validation and form data collection, you can also use a helper library. React form libraries simplify a lot of things, however, they also require some time to learn the API and to adapt a library to your UI framework. 

React Hook Form (RHF) is one of such libraries. It's based solely on react hooks and gives a nicer way of managing and validating your forms, no matter which UI framework you use. In SPFx we mostly use Fluent UI React (formerly Office UI Fabric). In this post, I'm going to show how you can configure React Hook Form so that it plays nicely with Fluent UI. More...

SharePoint Framework 1.9 introduced support for React 16.8+. While only a minor part of the version was changed (16.7 -> 16.8), it means a lot. It means that you can use the full power of React hooks. But should you? Obviously, the answer is yes, because React hooks introduce a lot of useful features, including:

• reuse stateful logic across your many React components, which isn't possible with class-based components
• get rid of high-order components, you can move some logic out of your React components into custom hooks. All that makes your code cleaner
• all your React components now are in the same style (you don't mix class-based components with functional). Instead, you use only functional components, because they support state (with help of hook of course)

There are even more reasons going to hooks, instead of class-based components. Check out official documentation from React:

Should I use Hooks, classes, or a mix of both?

....we’d encourage you to start trying Hooks in new components you write. ....In the longer term, we expect Hooks to be the primary way people write React components.

Hooks are available starting from February 2019. A lot of libraries adopted their code to hooks. You are on the safe side if you're planning to use hooks in your code today. More...