Callback or event for registration form validated and ready to be sent

Hi,

i need to launch a function when validation of the registration form is ok (basically i want to launch a php function or a JS one, when registration form is validated and before it is submitted).

This function will save user’s data and his consent to Privacy and terms on my DB as a proof of consent.

Can you suggest a way/example from your dev documentation, for doing it?

Note. I already have the function for saving data in my db, i need a way to attach it after the validation of the form and when it’s ready to be sent.

Thank you