Map Reduce with published_at limit

map-reduce.js

var mapFunction = function() {
  emit(this.facebook_object_id, 1);
};
 
var reduceFunction = function(key, values) {
  return Array.sum(values);
};
 
var options = {
  query: {published_at: {$gt: new Date(2013, 1, 1)}},
  out: {inline: 1},
};
 
function compare(v1, v2) {
  if (v1.value < v2.value) {
    return -1;
  } else if (v1.value > v2.value) {
    return 1;
  } else {
    return 0;
  }
}
 
var results = db.interactions.mapReduce(mapFunction, reduceFunction, options).results;
var sorted = results.sort(compare).reverse().splice(0, 25);