How to make inactive button on form submission if none of the form value has changed?

Question

React

There are several form fields with a submit button.
We do not use any libraries that simplify the work with forms.
I want that if the user did not change the values ​​of the fields, the button would be disabled.
If you change at least one, then make it active.

I could store initial values ​​​​in state and each time check if the value has changed (a form of 3 fields).
Is there a better and easier way to solve this problem?