I can't access the form fields to modify them

I am using “Laravel/Quasar”, I want to modify the “data” field when submitting a form in the “beforeSubmit” event.
I tried using “page.data” and “formData.data” but it doesn’t allow me to modify the value of the “data” field.
function beforeSubmit(){
page.data = “123”; //It doesn’t work
formData.data = “123”; //It doesn’t work
return true;
How can I access the form fields in the “beforeSubmit” event to modify them?

Excuse me, I was wrong. It is possible to access with “formData.data”.