prettier/tests/functional_composition/ramda_compose.js

var classyGreeting = (firstName, lastName) =>
  "The name's " + lastName + ", " + firstName + " " + lastName;
var yellGreeting = R.compose(R.toUpper, classyGreeting);
yellGreeting("James", "Bond"); //=> "THE NAME'S BOND, JAMES BOND"

R.compose(Math.abs, R.add(1), R.multiply(2))(-4); //=> 7

//  get :: String -> Object -> Maybe *
var get = R.curry((propName, obj) => Maybe(obj[propName]));

//  getStateCode :: Maybe String -> Maybe String
var getStateCode = R.composeK(
  R.compose(Maybe.of, R.toUpper),
  get("state"),
  get("address"),
  get("user")
);
getStateCode({ user: { address: { state: "ny" } } }); //=> Maybe.Just("NY")
getStateCode({}); //=> Maybe.Nothing()

var db = {
  users: {
    JOE: {
      name: "Joe",
      followers: ["STEVE", "SUZY"]
    }
  }
};

// We'll pretend to do a db lookup which returns a promise
var lookupUser = userId => Promise.resolve(db.users[userId]);
var lookupFollowers = user => Promise.resolve(user.followers);
lookupUser("JOE").then(lookupFollowers);

//  followersForUser :: String -> Promise [UserId]
var followersForUser = R.composeP(lookupFollowers, lookupUser);
followersForUser("JOE").then(followers => console.log("Followers:", followers));
// Followers: ["STEVE","SUZY"]