emberjs 按年月分组

 var groupByYearMonth = _.chain(topics).groupBy(function (item) { return item.TopicYear * 100 + item.TopicMonth }).map(function (value, key) {
                            return {
                                time: {
                                    year: value[0].TopicYear + ‘年‘,
                                    month: value[0].TopicMonth + ‘月‘
                                },
                                list: value
                            };
                        }).value();