node.js – mongoose“_id”字段无法删除

MongoDB: output ‘id’ instead of ‘_id’

以下是我的代码：

ScenicSpotSchema.virtual('id').get(function () {
    var id = this._id.toString();
    delete this._id;
    delete this.__v;
    return id;
});

但是响应仍然有字段“id”和“_id”,似乎删除没有生效.为什么？

schema.options.toJSON = {
  transform: function(doc, ret) {
    ret.id = ret._id;
    delete ret._id;
    delete ret.__v;
  }
};