When working with forms that require you to manage deeply nested data, React Hook Form provides a straightforward way to register and handle these fields. You can use dot notation in the name property when registering inputs to map them directly to nested objects in your form state. For example, if you have a user profile form with an address object, you can register an input like address.street to ensure the value is stored in the correct nested structure within your form data.

This approach allows you to work with complex data models without manual state manipulation. When you register a field using a name like user.contacts.email, React Hook Form automatically creates the nested object structure in the form values, so you do not need to flatten or reshape your data manually before submission.

Handling complex form data often means you need to match the structure your backend API expects. By leveraging dot notation for nested fields, you can keep your frontend form values aligned with your backend requirements. If your API expects an object with nested properties, registering your inputs using dot notation ensures the submitted data is already in the correct format. If the backend expects a different structure, you can map or transform the data in your form submission handler before sending it to the server.

For instance, suppose your backend requires an array of objects for a list of phone numbers, but your form collects them as separate fields. You can use the form's submission handler to transform the flat fields into the desired array structure before making an API call. This strategy keeps your form logic clean and focused on user interaction, while data transformation can be handled just before submission.

By understanding how to register nested fields and map complex data, you will be able to build forms that are both flexible for users and compatible with backend systems.