flatMapMaybe.js

// A common use for chaining Maybes is deep pulls on objects
// where there is uncertainty 

const { curry, Maybe, option } = crocks

const data = {
  happy: { joy: true }
}

// propMaybe : String -> Object -> Maybe
const propMaybe = curry(
  (prop, x) => Maybe(x[prop])
)

// pathMaybe : [ String ] -> Object -> Maybe
const pathMaybe = curry(
  (props, x) => props.reduce(
    (m, prop) => m.chain(propMaybe(prop)),
    Maybe(x)
  )
)

const path = [ 'happy', 'joy' ]
const nope = [ 'hapi', 'joi' ]

console.log(pathMaybe(path, data).option(false)) // valid returns true
console.log(pathMaybe(nope, data).option(false)) // not valid returns false (because of option)