Lens8

lens8.js

// immutable data
const addrs = List.of(Map({street: '99 Walnut Dr.', zip: '04821'}), Map({street: '2321 Crane Way', zip: '08082'}))
const user = Map({id: 3, name: 'bob', addresses: addrs})

// lenses
const addresses = immLens('addresses')
const street = immLens('street')
const allStreets = compose(addresses, mapped, street)

// getUser :: Int -> Task Error User
const getUser = id => new Task((rej, res) => setTimeout(() => res(user), 400))

// profilePage :: User -> Html
const profilePage = compose(map(x => `<span>${x.get('street')}<span>`), view(addresses))

// updateUser :: User -> User
const updateUser = over(allStreets, replace(/\d+/, '****'))

// renderProfile :: User -> Html
const renderProfile = compose(map(compose(profilePage, updateUser)), getUser)

renderProfile(1).fork(console.log, console.log)
//List [ "<span>**** Walnut Dr.<span>", "<span>**** Crane Way<span>" ]