listener.js

function listener(callback) {
  var objects = [1, 2, 3, 4, 5];

  objects = objects.map(function(o, i) {
    return o + 1;
  });

  // objects = [2, 3, 4, 5, 6] 
  return callback(objects);
}

listener(function(objects) {
   console.log("The result is:");
   console.log(objects);
});