Recursive iterating with promises; done "manually", and with when/unfold

iteratePromiseTest.js

'use strict';

var when = require('when'),
    delay = require('when/delay'),
    unfold = require('when/unfold');

function getNumber() {
  var deferred = when.defer();
  deferred.resolve(Math.floor(Math.random() * 10));
  return deferred.promise;
}

function chooseMessage(x) {
  if (x > 5) {
    return bigPromise(x);
  } else {
    return smallPromise(x);
  }
}

function bigPromise(x) {
  var deferred = when.defer();
  deferred.resolve(x + " is big");
  return deferred.promise;
}

function smallPromise(x) {
  var deferred = when.defer();
  deferred.resolve(x + " is small");
  return deferred.promise;
}

function display(x) {
  return when(console.log(x + "!"));
}


/* After http://stackoverflow.com/questions/17217736/ by Stuart Knightley (stuartk.com) */
function promiseWhile(condition, body) {
  var deferred = when.defer();

  function loop() {
    if (!condition()) {
      return deferred.resolve();
    }
    when(body(), loop, deferred.reject);
  }

  process.nextTick(loop);

  return deferred.promise;

}

function iteratePromiseWhile() {
  var i = 0;
  promiseWhile( function() { return i < 10 }, function() {
    i++;
    return when(i)
      .then(function(i) { console.log("i = " + i); })
      .then(getNumber)
      .then(chooseMessage)
      .then(display);
  }).then(
    function() { console.log('done'); }
  );
}

// using when.js' built-in unfold. Weird API but it works.
function iterateUnfold() {
  function unspool(i) {
    getNumber()
      .then(chooseMessage)
      .then(display);
    return ["did " + i, ++i];
  }
  function until10(i) {
    return i >= 10;
  }
  function handler(val) {
    console.log("handler " + val);
    return delay(1000);
  }
  console.log("hello");
  unfold(unspool, until10, handler, 0).then(function() {
    console.log("done!");
  });
}

// iteratePromiseWhile();
iterateUnfold();