如何在猫鼬中使用 find() 函数获取选定的输出？答案

【问题标题】：How to just get a the selected output using find() function in mongoose?如何在猫鼬中使用 find() 函数获取选定的输出？
【发布时间】：2021-05-28 16:10:48
【问题描述】：

我已经执行了这段代码

 db.courses.find({isPublished: true , tags: "backend"} , {name: 1 , author:1}).sort({name: 1})

在 MongoDB shell 中，它给了我所需的输出。现在我正在尝试使用猫鼬执行相同的代码，它给了我这个

[
  model {
    '$__': InternalCache {
      strictMode: true,
      selected: [Object],
      shardval: undefined,
      saveError: undefined,
      validationError: undefined,
      adhocPaths: undefined,
      removing: undefined,
      inserting: undefined,
      version: undefined,
      getters: {},
      _id: 5a68fde3f09ad7646ddec17e,
      populate: undefined,
      populated: undefined,
      wasPopulated: false,
      scope: undefined,
      activePaths: [StateMachine],
      pathsToScopes: {},
      ownerDocument: undefined,
      fullPath: undefined,
      emitter: [EventEmitter],
      '$options': true
    },
    isNew: false,
    errors: undefined,
    _doc: {
      _id: 5a68fde3f09ad7646ddec17e,
      name: 'ASP.NET MVC Course',
      author: 'Mosh'
    },
    '$init': true
  },
  model {
    '$__': InternalCache {
      strictMode: true,
      selected: [Object],
      shardval: undefined,
      saveError: undefined,
      validationError: undefined,
      adhocPaths: undefined,
      removing: undefined,
      inserting: undefined,
      version: undefined,
      getters: {},
      _id: 5a68fdc3615eda645bc6bdec,
      populate: undefined,
      populated: undefined,
      wasPopulated: false,
      scope: undefined,
      activePaths: [StateMachine],
      pathsToScopes: {},
      ownerDocument: undefined,
      fullPath: undefined,
      emitter: [EventEmitter],
      '$options': true
    },
    isNew: false,
    errors: undefined,
    _doc: {
      _id: 5a68fdc3615eda645bc6bdec,
      name: 'Express.js Course',
      author: 'Mosh'
    },
    '$init': true
  },
  model {
    '$__': InternalCache {
      strictMode: true,
      selected: [Object],
      shardval: undefined,
      saveError: undefined,
      validationError: undefined,
      adhocPaths: undefined,
      removing: undefined,
      inserting: undefined,
      version: undefined,
      getters: {},
      _id: 5a68fdd7bee8ea64649c2777,
      populate: undefined,
      populated: undefined,
      wasPopulated: false,
      scope: undefined,
      activePaths: [StateMachine],
      pathsToScopes: {},
      ownerDocument: undefined,
      fullPath: undefined,
      emitter: [EventEmitter],
      '$options': true
    },
    isNew: false,
    errors: undefined,
    _doc: {
      _id: 5a68fdd7bee8ea64649c2777,
      name: 'Node.js Course',
      author: 'Mosh'
    },
    '$init': true
  },
  model {
    '$__': InternalCache {
      strictMode: true,
      selected: [Object],
      shardval: undefined,
      saveError: undefined,
      validationError: undefined,
      adhocPaths: undefined,
      removing: undefined,
      inserting: undefined,
      version: undefined,
      getters: {},
      _id: 5a68fe2142ae6a6482c4c9cb,
      populate: undefined,
      populated: undefined,
      wasPopulated: false,
      scope: undefined,
      activePaths: [StateMachine],
      pathsToScopes: {},
      ownerDocument: undefined,
      fullPath: undefined,
      emitter: [EventEmitter],
      '$options': true
    },
    isNew: false,
    errors: undefined,
    _doc: {
      _id: 5a68fe2142ae6a6482c4c9cb,
      name: 'Node.js Course by Jack',
      author: 'Jack'
    },
    '$init': true
  }
]

虽然它给了我所需的输出以及一些额外的难以理解的东西，这使得它不可读。我实际上正在学习 NodeJS 课程，其中讲师使用 Mac，他的输出与 MongoDB 输出相同。我的代码在javascript是

 const mongoose = require("mongoose"); 


const fun = async() => {

    await mongoose.connect("mongodb://localhost:27017/Exercise"); 

    const schema  = mongoose.Schema({
        name: String , 
        author: String , 
        tags: [String] ,
        date: Date , 
        isPublished: Boolean , 
        price: Number 
    }); 

    const Course = mongoose.model("Course" , schema); 

    const result = await Course.find({isPublished: true
        , tags: "backend"})
        .sort({name: 1 })
    .select({name: 1  , author: 1 }); 

    console.log(result); 

}
fun();

【问题讨论】：

标签： javascript node.js mongodb mongoose nosql

【解决方案1】：

您需要将 Mongoose 模型转换为对象。

您可以使用lea() 函数转换为对象。

const result = await Course.find({isPublished: true
        , tags: "backend"})
        .sort({name: 1 })
    .select({name: 1  , author: 1 })
.lean()

也可以通过其他方式实现，

let result = await Course.find({isPublished: true
        , tags: "backend"})
        .sort({name: 1 })
    .select({name: 1  , author: 1 })
result = result.map(r => r.toObject())

【讨论】：