Error handling

Most validation failures throw specific errors. Catch the specific error when code needs to distinguish between invalid value categories.

import { Email, InvalidEmailError } from '@haskou/value-objects';

try {
  new Email('invalid');
} catch (error) {
  if (error instanceof InvalidEmailError) {
    // Invalid email format.
  }
}

Common errors

Error	Usually thrown by
InvalidStringLengthError	StringValueObject
InvalidPasswordError	Password
InvalidNumberError	NumberValueObject
InvalidIntegerError	Integer, Year, Day
InvalidPositiveNumberError	PositiveNumber
InvalidEmailError	Email
InvalidColorError	Color
InvalidLengthError	IDs, keys, payloads
InvalidFormatError	IDs, keys, payloads
InvalidHashError	Hash classes
InvalidDayError	Day, CalendarDay, DayOfWeek
InvalidDayFormatError	CalendarDay
InvalidHourError	Hour
InvalidMinutesError	Hour
InvalidTimestampIntervalError	TimestampInterval
ValueNotInEnumError	Enum subclasses
NullObjectError	Calling a fake method on a null object

Pattern

function parseEmail(value: string): Email | null {
  try {
    return new Email(value);
  } catch (error) {
    if (error instanceof InvalidEmailError) {
      return null;
    }

    throw error;
  }
}

Keep catch blocks narrow. Broadly swallowing validation errors is how data quality goes to die quietly in production.