fallbackAsync

Returns a fallback value as output if the input does not match the schema.

const Schema = v.fallbackAsync<TSchema, TFallback>(schema, fallback);

Generics

• TSchema extends BaseSchema<unknown, unknown, BaseIssue<unknown>> | BaseSchemaAsync<unknown, unknown, BaseIssue<unknown>>
• TFallback extends FallbackAsync<TSchema>

Parameters

• schema TSchema
• fallback TFallback

Explanation

fallbackAsync allows you to define a fallback value for the output that will be used if the validation of the input fails. This means that no issues will be returned when using fallbackAsync and the schema will always return an output.

If you only want to set a default value for null or undefined inputs, you should use optionalAsync, nullableAsync or nullishAsync instead.

The fallback value is not validated. Make sure that the fallback value matches your schema.

Returns

• Schema SchemaWithFallbackAsync<TSchema, TFallback>

Examples

The following examples show how fallbackAsync can be used.

Unique username schema

Schema that will always return a unique username.

By using a function as the fallbackAsync parameter, the schema will return any unique username each time the input does not match the schema.

import { getAnyUniqueUsername, isUsernameUnique } from '~/api';

const UniqueUsernameSchema = v.fallbackAsync(
  v.pipeAsync(v.string(), v.minLength(4), v.checkAsync(isUsernameUnique)),
  getAnyUniqueUsername
);

Related

The following APIs can be combined with fallbackAsync.

Schemas

• any,
• array,
• bigint,
• blob,
• boolean,
• custom,
• date,
• enum,
• file,
• function,
• instance,
• intersect,
• lazy,
• literal,
• looseObject,
• looseTuple,
• map,
• nan,
• never,
• nonNullable,
• nonNullish,
• nonOptional,
• null,
• nullable,
• nullish,
• number,
• object,
• objectWithRest,
• optional,
• picklist,
• promise,
• record,
• set,
• strictObject,
• strictTuple,
• string,
• symbol,
• tuple,
• tupleWithRest,
• undefined,
• undefinedable,
• union,
• unknown,
• variant,
• void

Methods

• config,
• getDefault,
• getFallback,
• keyof,
• omit,
• pick,
• unwrap

Actions

• base64,
• bic,
• brand,
• bytes,
• check,
• checkItems,
• creditCard,
• cuid2,
• decimal,
• description,
• digits,
• email,
• emoji,
• empty,
• endsWith,
• everyItem,
• excludes,
• filterItems,
• findItem,
• finite,
• graphemes,
• hash,
• hexadecimal,
• hexColor,
• imei,
• includes,
• integer,
• ip,
• ipv4,
• ipv6,
• isoDate,
• isoDateTime,
• isoTime,
• isoTimeSecond,
• isoTimestamp,
• isoWeek,
• length,
• mac,
• mac48,
• mac64,
• mapItems,
• maxBytes,
• maxGraphemes,
• maxLength,
• maxSize,
• maxValue,
• maxWords,
• metadata,
• mimeType,
• minBytes,
• minGraphemes,
• minLength,
• minSize,
• minValue,
• minWords,
• multipleOf,
• nanoid,
• nonEmpty,
• notBytes,
• notGraphemes,
• notLength,
• notSize,
• notValue,
• notWords,
• octal,
• partialCheck,
• rawCheck,
• rawTransform,
• readonly,
• reduceItems,
• regex,
• safeInteger,
• size,
• someItem,
• sortItem,
• startsWith,
• title,
• toLowerCase,
• toMaxValue,
• toMinValue,
• toUpperCase,
• transform,
• trim,
• trimEnd,
• trimStart,
• ulid,
• url,
• uuid,
• value,
• words

Utils

• isOfKind,
• isOfType

Async

• arrayAsync,
• checkAsync,
• customAsync,
• getDefaultsAsync,
• getFallbacksAsync,
• intersectAsync,
• lazyAsync,
• looseObjectAsync,
• looseTupleAsync,
• mapAsync,
• nonNullableAsync,
• nonNullishAsync,
• nonOptionalAsync,
• nullableAsync,
• nullishAsync,
• objectAsync,
• objectWithRestAsync,
• optionalAsync,
• parseAsync,
• parserAsync,
• partialAsync,
• partialCheckAsync,
• pipeAsync,
• rawCheckAsync,
• rawTransformAsync,
• recordAsync,
• requiredAsync,
• safeParseAsync,
• safeParserAsync,
• setAsync,
• strictObjectAsync,
• strictTupleAsync,
• transformAsync,
• tupleAsync,
• tupleWithRestAsync,
• unionAsync,
• variantAsync