Code sample from Algebraic Javascript

data.js

const recs = [
  { learner: 'Joan', score: 84 },
  null,
  { learner: null, score: 97 },
  { learner: 'Thomas', score: 72 },
  22,
  { learner: 'Bob', score: 92 }
  { learner: 'Joey', score: 62 },
]

export default recs

index.js

import {
  and, chain, compose, constant, fanout,
  getProp, isNumber, isString, liftA2,
  maybeToArray, merge, propSatisfies, safe
} from 'crocks'

import data from './data'

// gte :: Number -> Number -> Boolean
const gte = a => b =>
  b >= a

// validScore :: Number -> (a -> Boolean)
const validScore =
  compose(and(isNumber), gte)

// passesWith :: Number -> Record -> Maybe Record
const passesWith = compose(
  safe,
  propSatisfies('score'),
  validScore
)

// validLearner :: Record -> Boolean
const validLearner =
  and(isString, propSatisfies('length', gte(4)))

// validateLearner :: (Record -> Boolean) -> Record -> Maybe String
const validateLearner = test => compose(
  chain(safe(test)),
  getProp('learner')
)

// validRecord :: Record -> Pair (Maybe String) (Naybe Record)
const validRecord = fanout(
  validateLearner(validLearner),
  passesWith(70),
)

// validateRecord :: Record -> Maybe String
const validateRecord = compose(
  merge(liftA2(constant)),
  validRecord
)

// program :: [ Record ] -> [ String ]
const program =
  chain(maybeToArray(validateRecord))

console.log(data)
console.log(
  program(data)
)