Created
January 20, 2022 15:04
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| /** | |
| * We could use `Either<string, T>` as a validaiton result. But the problem is, | |
| * we wouldn't be able to accumulate the errors. The `Validation` types enables | |
| * that for us. | |
| * | |
| * ```ts | |
| * type Validation<E, T> = Either<NonEmptyArray<E>, T> | |
| * ``` | |
| * | |
| * @example | |
| * import * as Either from 'fp-ts/Either'; | |
| * import { pipe } from 'fp-ts/function'; | |
| * import { sequenceT } from 'fp-ts/Apply'; | |
| * import { getSemigroup, NonEmptyArray } from 'fp-ts/NonEmptyArray'; | |
| * | |
| * const notAllowedUrls = (s: string) => | |
| * s.includes('facebook') ? Either.left('Not allowed') : Either.right(s); | |
| * | |
| * const wordLimit = (s: string) => | |
| * s.split(' ').length > 5 ? Either.left('Too many words') : Either.right(s); | |
| * | |
| * const hasBannedWords = (s: string) => | |
| * s.includes('BAD_WORD') ? Either.left('Includes bad word') : Either.right(s); | |
| * | |
| * const applicativeValidation = | |
| * Either.getApplicativeValidation(getSemigroup<string>()); | |
| * | |
| * const validateText = (s: string) => | |
| * pipe( | |
| * sequenceT(applicativeValidation)( | |
| * liftValidation(notAllowedUrls)(s), | |
| * liftValidation(wordLimit)(s), | |
| * liftValidation(hasBannedWords)(s) | |
| * ), | |
| * Either.map(() => s) | |
| * ); | |
| * | |
| * validateText('BAD_WORD one two three four five six'); | |
| * //=> Either.left(['Too many words', 'Includes bad word']) | |
| * | |
| * validateText('I am good'); | |
| * //=> Either.right('I am good') | |
| */ | |
| export function liftValidation<E, A>( | |
| check: (a: A) => Either.Either<E, A> | |
| ): (a: A) => Either.Either<NonEmptyArray.NonEmptyArray<E>, A> { | |
| return (a) => | |
| pipe( | |
| check(a), | |
| Either.mapLeft((a) => [a]) | |
| ); | |
| } |
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