我有两个集合，一个是用户，另一个是猫。我希望猫的数据下我的用户集合。但我没有得到。
User.js

var Schema = mongoose.Schema;
var userSchema = Schema({
_id: Schema.Types.ObjectId,
username: String,
email: { type: String, unique: true, lowercase: true, trim: true },
password: String,
role: String,
cats: [{ type: Schema.ObjectId, ref: 'Cat' }]
});
var User = mongoose.model('User', userSchema);
exports.default = User;

Cat.js

var mongoose = require("mongoose");
var Schema = mongoose.Schema;
var catSchema = Schema({
fname: String,
mname: String,
lname: String,
});
var Cat = mongoose.model('Cat', catSchema);
exports.default = Cat;

O/p
"_id" : ObjectId("5a446ab43533970b8489e1ac"), "username" : "xyz", "email" : "xyz@gmail.com", "password""$2a$10$ogerY6OiCRKy9TjPYERaOugUJeqelBl.yToJ4ZBX3ac2MVZQpsKOu", "role" : "user", "cats" : [ ], "__v" : 0
预期输出
"_id" : ObjectId("5a446ab43533970b8489e1ac"), "username" : "xyz", "email" : "xyz@gmail.com", "password""$2a$10$ogerY6OiCRKy9TjPYERaOugUJeqelBl.yToJ4ZBX3ac2MVZQpsKOu", "role" : "user", "cats" : [{ "_id" : ObjectId("5a44707effc66a234447c36b"), "fname" : "felix", "mname" : "", "lname" : "", } ], "__v" : 0