现在有多行数据，有科目、主体、日期字段，现在通过js将科目和主体进行分组，按日期字段大小从小到大排序

好的，我可以为您提供代码示例，假设您的数据如下所示：

const data = [
  { subject: "Math", entity: "A", date: "2021-01-01" },
  { subject: "Math", entity: "B", date: "2021-02-01" },
  { subject: "Science", entity: "C", date: "2021-03-01" },
  { subject: "Science", entity: "D", date: "2021-01-15" },
  { subject: "Math", entity: "E", date: "2021-04-01" },
  { subject: "Science", entity: "F", date: "2021-02-15" }
];

现在我们可以按照科目和主体进行分组，代码如下所示：

const groupedData = data.reduce((acc, curr) => {
  const key = curr.subject + "_" + curr.entity;
  if (!acc[key]) {
    acc[key] = [curr];
  } else {
    acc[key].push(curr);
  }
  return acc;
}, {});

接下来我们可以对每个组内的数据按日期从小到大排序，代码如下所示：

Object.values(groupedData).forEach((group) => {
  group.sort((a, b) => new Date(a.date) - new Date(b.date));
});

最后，我们可以将结果打印出来，代码如下所示：

console.log(groupedData);

输出结果如下：

{
  "Math_A": [{ subject: "Math", entity: "A", date: "2021-01-01" }],
  "Math_B": [{ subject: "Math", entity: "B", date: "2021-02-01" }],
  "Math_E": [{ subject: "Math", entity: "E", date: "2021-04-01" }],
  "Science_C": [{ subject: "Science", entity: "C", date: "2021-03-01" }],
  "Science_D": [{ subject: "Science", entity: "D", date: "2021-01-15" }],
  "Science_F": [{ subject: "Science", entity: "F", date: "2021-02-15" }]
}

其中，每个组内的数据按照日期从小到大排序。希望这个代码示例能够对您有所帮助。