Clarity of intend

intend.js

function getUser(id) {
  // implementation unknown
}

function getUserName(id) {
  // is getUser(id) returning Promise[String]? String? - both work fine
  return when(when(id, getUser), function(user) {
    return user.name;
  });
}

function findLongest(values) {
  // returns value with max value.length
}

var mixed = [ // user ids from different sources
  'foo',
  Promise.resolve('bar'),
  10
];

// we don't have to care about whether it's a value or a
// promise of a value - conceptually (in the problem domain)
// it's some user's id. the fact that the when-call above is
// "automagically" unifying the types lets us focus on expressing
// the actual problem instead of talking about non-domain
// abstractions
var names = mixed.map(getUserName); // Array[Promise[String]
all(names, findLongest).then(function(longestName) {
  console.log(longestName);
});