What to do instead of [for (var in collection)]

map vs for

getSomeThings().then(function(things){
  return things.map(function(aThing){
    return OtherThing.find(aThing.id);
  });
});

//Replaces
var thingIx, newThing, otherThings
getSomeThings()
.then(function(collection){
  for(thingIx in collection) {
    var newThing = OtherThing.find(collection[thingIx].id)
    otherThings.push(newThing)
  }
)}