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Function: mapInvalid()

Call Signature​

mapInvalid<T, E, F>(validation, fn): Validation<T, F>

Defined in: validation/mapInvalid/index.ts:60

Maps over the Invalid errors of a Validation.

If the validation is Invalid, applies the function to each error. If the validation is Valid, returns it unchanged.

Type Parameters​

T​

T

E​

E

F​

F

Parameters​

validation​

Validation<T, E>

The validation to map over

fn​

(error) => F

Function to transform each error

Returns​

Validation<T, F>

A new validation with transformed errors

Example​

// Data-first
mapInvalid(invalid(['error1', 'error2']), e => e.toUpperCase())
// => Invalid(['ERROR1', 'ERROR2'])

mapInvalid(valid(42), e => e.toUpperCase())
// => Valid(42)

// Data-last (in pipe)
pipe(
  invalid(['error1', 'error2']),
  mapInvalid(e => e.toUpperCase())
) // => Invalid(['ERROR1', 'ERROR2'])

// Real-world: Add context to errors
const validateForm = (data: FormData) =>
  pipe(
    validateEmail(data.email),
    mapInvalid(err => ({ field: 'email', message: err }))
  )

// Transform error types
const toApiError = (err: string): ApiError => ({
  code: 'VALIDATION_ERROR',
  message: err,
  timestamp: Date.now()
})

pipe(
  validateInput(input),
  mapInvalid(toApiError)
)

See​

  • map - for transforming valid values
  • flatMap - for chaining validations

Call Signature​

mapInvalid<E, F>(fn): <T>(validation) => Validation<T, F>

Defined in: validation/mapInvalid/index.ts:64

Maps over the Invalid errors of a Validation.

If the validation is Invalid, applies the function to each error. If the validation is Valid, returns it unchanged.

Type Parameters​

E​

E

F​

F

Parameters​

fn​

(error) => F

Function to transform each error

Returns​

A new validation with transformed errors

<T>(validation): Validation<T, F>

Type Parameters​

T​

T

Parameters​

validation​

Validation<T, E>

Returns​

Validation<T, F>

Example​

// Data-first
mapInvalid(invalid(['error1', 'error2']), e => e.toUpperCase())
// => Invalid(['ERROR1', 'ERROR2'])

mapInvalid(valid(42), e => e.toUpperCase())
// => Valid(42)

// Data-last (in pipe)
pipe(
  invalid(['error1', 'error2']),
  mapInvalid(e => e.toUpperCase())
) // => Invalid(['ERROR1', 'ERROR2'])

// Real-world: Add context to errors
const validateForm = (data: FormData) =>
  pipe(
    validateEmail(data.email),
    mapInvalid(err => ({ field: 'email', message: err }))
  )

// Transform error types
const toApiError = (err: string): ApiError => ({
  code: 'VALIDATION_ERROR',
  message: err,
  timestamp: Date.now()
})

pipe(
  validateInput(input),
  mapInvalid(toApiError)
)

See​

  • map - for transforming valid values
  • flatMap - for chaining validations