将对象数组过滤为对象

减少这样的数据:

var arrayData = [{"id":1, "subid":5}, {"id":1, "subid":9}, {"id":2, "subid":16}, {"id":2, "subid":27}];

var result = arrayData.reduce(function (result, obj) {
  var id = obj.id;
  result[id] = (result[id] || []);
  result[id].push(obj.subid);
  return result;
}, {});