How to watch an array field in react hook form?

Question

i am migrating an existing complex react app using react-final-form to use react-hook-form and i don't know how to implement something like decorators used in final-form.

For example i have multiple decorators that transform a field when another changes.

Decorator example:

 field: [/array\[\d+\]\.anotherArray\[\d+\]\.field/]

It's so easy using final-form but i didn't find an answer using watch