add support for onChange

[jeremyjs]

in addition to onSubmit. one use case is for a form that auto-saves on every change or blur of a sub-element.

[bastibuck]

You could probably use the watch of react-hook-form like here. Create your form and pass it.

https://react-ts-form.com/docs/docs/usage/form-state
https://react-hook-form.com/docs/useform/watch