dewey92

const array = createMonoid({
  indentity: [],
  semigroup: (a, b) => a.concat(b),
});

log(array.id) // => []
log(array.append([1], [2])) // => [1, 2]
log(array.append([1, 2], array.id)) // => [1, 2]

dewey92

const string = createMonoid({
  indentity: '',
  semigroup: (a, b) => a + b,
});

log(string.id) // => ''
log(string.append('Foo', 'Bar')) // => FoorBar
log(string.append('Foo', string.id)) // => Foo

dewey92

const numMult = createMonoid({
  indentity: 1,
  semigroup: (a, b) => a * b,
});

log(numMult.id) // => 1
log(numMult.append(1, 999)) // => 999
log(numMult.append(999, numMult.id)) // => 999

dewey92

const numAddition = createMonoid({
  indentity: 0,
  semigroup: (a, b) => a + b,
});

log(numAddition.id) // => 0
log(numAddition.append(1, 2)) // => 3
log(numAddition.append(3, numAddition.id)) // => 3

dewey92

const memoize = fn => {
  const cache = {}
  return (…args) => {
    const stringifiedArgs = JSON.stringify(args)
    const result = cache[stringifiedArgs] || fn(…args)
    cache[stringifiedArgs] = result
    return result
  }
}

dewey92

const liftA2 = f => (m, n) => m.map(f).ap(n);

const add = x => y => x + y;
const monadicAdd = liftA2(add);

add(5, 6) // 11
monadicAdd(Just(5), Just(6)) // Just(11)

dewey92

const FORM_ID = 'personal-details'

// Factory
const onChange = (fieldName: string) => e => {
  notifyParentOnFieldChange(FORM_ID, fieldName)

  // actual computaion
  const value = e.target.value
  ...
}

dewey92

const fillNames = (firstN, middleN, lastN) =>
  firstN + middleN + lastN

const a = fillNames.bind(null, 'Jihad');
const b = a(' Dzikri', ' Waspada')

b === 'Jihad Dzikri Waspada' // true

dewey92

const add = x => y => x + y

const identity = add(0)
const increment = add(1)
const decrement = add(-1)

identity(7)  // 7
increment(7) // 8
decrement(7) // 6

dewey92

const fillNames = firstN => middleN => lastN =>
  firstN + middleN + lastN

const a = fillNames('Jihad');
const b = a(' Dzikri')(' Waspada')

b === 'Jihad Dzikri Waspada' // true