如何在mongoose中使用$map和find

const mongoose = require('mongoose');

const mySchema = new mongoose.Schema({
  myArray: [{
    name: String,
    age: Number
  }]
});

const MyModel = mongoose.model('MyModel', mySchema);

MyModel.aggregate([
  {
    $project: {
      mappedArray: {
        $map: {
          input: {
            $filter: {
              input: '$myArray',
              as: 'item',
              cond: { $gte: ['$$item.age', 18] }
            }
          },
          as: 'item',
          in: {
            name: '$$item.name',
            age: '$$item.age'
          }
        }
      }
    }
  }
])
.exec((err, result) => {
  if (err) {
    console.error(err);
  } else {
    console.log(result);
  }
});