node.js - Object.assign() 在分配 mongoose 文档时创建奇怪的属性

Question

MessageThread.findById(req.body._id)
      .populate({ path: "messages" })
      .exec((err, foundMessageThread) => {
        var filtered = foundMessageThread.messages.map(message=>{
          return Object.assign({}, message, {isRead: true});
        })
        console.log("filtered", filtered);

      });

console.log 显示:

{ '$__':
 InternalCache {
   strictMode: true,
   selected: {},
   shardval: undefined,
   saveError: undefined,
   validationError: undefined,
   adhocPaths: undefined,
   removing: undefined,
   inserting: undefined,
   version: undefined,
   getters: {},
   _id: 5a4c7f2d8b49fc260c396f55,
   populate: undefined,
   populated: undefined,
   wasPopulated: true,
   scope: undefined,
   activePaths: [Object],
   pathsToScopes: {},
   ownerDocument: undefined,
   fullPath: undefined,
   emitter: [Object],
   '$options': true },
isNew: false,
errors: undefined,
_doc:
 { sentAt: 2018-01-03T06:58:53.188Z,
   isRead: false,
   _id: 5a4c7f2d8b49fc260c396f55,
   sender: 5a4b77767251b44cd870219f,
   reciever: 5a4b780a7251b44cd87021a1,
   text: 'qwe',
   __v: 0 },
'$init': true,
isRead: true },
......

它重复了很多次。我想它 (InternalCache { strictMode: true...) 与从 foundMessageThread 获取的 message 相关。它在分配时揭示了它的元数据(在我的术语中)。因为:

MessageThread.findById(req.body._id)
  .populate({ path: "messages" })
  .exec((err, foundMessageThread) => {
    var filtered = foundMessageThread.messages.map(message=>{
      console.log("message", message)
      return Object.assign({}, message, {isRead: true});
    })
    console.log("filtered", filtered);

  });

console.log 显示

{ sentAt: 2018-01-03T06:58:53.188Z,
  isRead: false,
  _id: 5a4c7f2d8b49fc260c396f55,
  sender: 5a4b77767251b44cd870219f,
  reciever: 5a4b780a7251b44cd87021a1,
  text: 'qwe',
  __v: 0 },
....

我的问题:

1. 这是正常行为吗？
2. 如果是怎么解决？因为“元数据”阻止了对象的分配。

附言我试过:

MessageThread.findById(req.body._id)
  .populate({ path: "messages" })
  .exec((err, foundMessageThread) => {
    var filtered = foundMessageThread.messages.map(message=>{
      return **Object.assign({}, message._doc, {isRead: true})**;
    })
    console.log("filtered", filtered);

  });

Answer 1

这是 Mongoose 的正常行为。 mongoose 返回的对象包装了实际数据，以便向其添加行为(方法)。

您可以使用toObject 方法获取实际的数据对象，例如，message.toObject()。

然而，有像 __v 这样的属性，mongoose 使用它们来进行内务管理。如果你不想要它们，你可以像这样修改 toObject 方法

messageSchema.set('toObject', {
  versionKey: false,
  transform: (doc, ret) => {
    delete ret.__v;
    return ret;
  },
});