reducers.js

const customers = [
  { name: 'foo', orders: 4 },
  { name: 'bar', orders: 3 },
  { name: 'baz', orders: 2 },
  { name: 'qux', orders: 1 }
]

const arrayReducer = (arr, elem) => arr.concat(elem)

const tmap =
  transform =>
    reducer =>
      (memo, curr) =>
        reducer(memo, transform(curr))

const tfilter =
  predicate =>
    reducer =>
      (memo, curr) =>
        predicate(curr) ? reducer(memo, curr) : memo


const isGreat = customer => customer.orders > 2
const getCustomerName =
  customer =>
    isGreat(customer)
      ? `${customer.name} the great`
      : `${customer.name} the tiny`
const warriorNameTransducer = tmap(getCustomerName)
const upperCaseTransducer = tmap(s => s.toUpperCase())
const isGreatFilterTransducer = tfilter(isGreat)

const flow = (...fns) => (arg) => fns.reduce((a, f) => f(a), arg)
const flowRight = (...fns) => (arg) => fns.reduceRight((a, f) => f(a), arg)

console.log(
  customers.reduce(
    flowRight(
      isGreatFilterTransducer,
      warriorNameTransducer,
      upperCaseTransducer,
    )(arrayReducer), []
  )
)