for (var i = 0; i < fields.length; i++)
           {
               if(fields[i].changed())
               {
                   for (var j = 0; j < fields[i].constraints.length; j++)
                   {
                        if(fields[i].constraints[j].fails()) 
                        {
                            throw error.create
                            ({
                                name: constraint.errorDetails.name,
                                message: constraint.errorDetails.message
                            });
                        }
                   }
               }
           }