Fire an event when the user edits/adds something in the json-editor

I want to block the form's save button when the user is editing the json in any way (adding new keys, editing a single value or an entire object, etc) to force them to undo/accept the changes in the editor before saving the entire form. 

I think the easiest way to achieve this, is to fire an event when the user edits/adds something, allowing me to control the lock/unlock state of the button.