gistfile1.js

var a = null;
var promise = somethingLongTahtReturnsAPromise();

function chainToAndSet(promise) {
  promise.then(function(values) { a = values })
  return promise;
}

function sort() {
  new Promise(function(values) { _.sort(values) }
}

chainToAndSet(promise).then(sort()); // a will not be sorted

// -----------------

// What you want to be able to do
promise.then(function(values) { values[0..10] }).then(sort());

// And in your view just say
{{promise.value}}
// Which will fill in once the promise is fulfilled, and you dont care what is in the chain