Zod Optional Empty Field

The Snippets

const emptyStringToUndefined = z.literal('').transform(() => undefined);
export function asOptionalField<T extends z.ZodTypeAny>(schema: T) {
  return schema.optional().or(emptyStringToUndefined);
}

The emptyStringToUndefined uses z.literal("") schema to represent a literal empty string. The transform method is the used to convert the empty string to undefined.

The function asOptionalField takes a zod schema as its parameter. It then makes use of the zod optional method to make the field optional, and it combines this with the or method to include the emptyStringToUndefined transform. This means that the resulting schema will accept either the original value, or an empty string (which will be transformed to undefined).

In summary, the asOptionalField function is designed to take any Zod schema and make it optional, allowing it to accept either the original value or an empty string (transformed to undefined). This can be useful when dealing with optional fields in data validation scenarios.

How to Use

export const editProfileSchema = z.object({
  username: z.string(),
  email: z.string().email(),
  whatsapp: asOptionalField(
    z
      .string()
      .min(9, { message: 'Whatsapp number minimum 9 digits' })
      .max(14, { message: 'Whatsapp number minimum 9 digits' })
      .startsWith('08', { message: 'Not valid Whatsapp number' })
      .regex(/^[0-9]*$/, { message: 'Not valid Whatsapp number' }),
  ),
});

In this context, we utilize the asOptionalField to validate the input of a WhatsApp number. The methods min(), max(), startsWith(), and regex() will only be invoked if the WhatsApp number input is neither undefined nor an empty string ("").