code: @Nonnull
    public JSFieldVar field (@Nonnull @Nonempty final String sName, @Nullable final IJSExpression aInit)
    {
      final JSFieldVar aField = new JSFieldVar (this, sName, aInit);
      return addField (aField);
    }
docs: Adds a field to the list of field members of this defined class.
  
  @param sName
  Name of this field.
  @param aInit
  Initial value of this field.
  @return Newly generated field