// define a schema
  const personSchema = new Schema({
    name: {
      first: String,
      last: String
    }
  },
  {
    toJSON: {
      virtuals: true,
    },
    toObject: {
      virtuals: true,
    },
  },);
personSchema.virtual('fullName').
  get(function() {
    return this.name.first + ' ' + this.name.last;
    }).
  set(function(v) {
    this.name.first = v.substr(0, v.indexOf(' '));
    this.name.last = v.substr(v.indexOf(' ') + 1);
  });

  // compile our model
  const Person = mongoose.model('Person', personSchema);

这是从文档中定义的#virtuals
让我们来看另一个与person相关的模型：

const shopSchema = new Schema({
    name:String,
    owner: { type: Schema.Types.ObjectId, ref: "Person" },
  });
const Shop = mongoose.model('Shop', shopSchema);

现在，如何获得 fullName 虚拟商店 owner . 在这里，所有者不包括 fullName ```
const getAllData = async () => {
const shops = await Shop.find().populate("owner").lean();
console.log(shops)
}