在下面的代码中，我正在等待猫鼬的数据库调用解决。即使这样，最终声明 res.json({err: null,data: studentArray})在上述循环完成之前执行。

这是该功能的完整代码。

router.post("/",moderator,(req,res) => {
 const { filters } = req.body;
  const { students } = filters;
  const studentArray = [];
  try {
    if (students.branches) {
      students.branches.forEach(async branch => {
        const departments = await Department.find({ name: branch });
        departments.forEach(async dept => {
          const studentPerBranch = await Student.find({ branch: dept.id });
          // console.log(studentPerBranch);
          studentArray.push(studentPerBranch);
        });
      });
      res.json({ err: null,data: studentArray });
    } else res.status(404).json({ err: "Branches not found" });
  } catch (err) {
    res.status(500).json({ err,data: null });
  }
});