How to update a field based on the current locale that is being edited?

I’m trying to create an app (using the App Framework) that autofills some fields and I need a way to update a field for the current locale that the user is editing, ex: If the user is editing the English locale then I want to update the field only for that locale; I want to achieve the same behavior if the user is editing the Spanish locale;

I have not found in the App SDK a way to know what is the current locale that the user is editing.
I am looking for something like this:

sdk.entry.fields.myField.setValue(value, localeBeingEdited)