获取一个空数组猫鼬

我无法通过猫鼬从MongoDb集合中获取数据-我从请求中获取了一个空数组。仅当我使用下面发布的路线时才会发生。码

router.get("/options", async (req,res) => {
  try {
    const { animalClass} = req.body;
    if (!animalClass) {
    const animalClasses = await AnimalClass.find({});
    console.log(animalClasses);

    return res
      .status(200)
      .json({animalClasses})

    } else {
      const animalTypes = await AnimalType.find({class: animalClass});
      console.log(animalTypes);

      return res
        .status(200)
        .json({animalTypes})
    }

  } catch (err) {
    res
      .status(500)
      .json({msg: err})
  }
});

架构图

const mongoose = require('mongoose');

const animalClassSchema = new mongoose.Schema({
  name: {type: String, required: true}
})

module.exports = AnimalClass = mongoose.model('animalClass',animalClassSchema);