Rather have code that looks like this:

  toggleDropdown(field) {
   if ...
  }
  
  toggleDropdown(_protected.fields[field]);

Also the external documentation wouldn't have anything like this in it. It would be pretty much:

  UI Code is in XXX. It communicates with ZZZ using YYY. 
  Fields in the UI are changed between text and dropdowns 
  depending on the value in the database that comes 
  from ZZZ. etc.