JavaScript: dynamic property not showing unless accessed explicitly

Question

I'm using NodeJs, I'm creating a dynamic property inside an object, and then pushing it into an array. The problem is, when I access the variable via console.log(object[dynamic_property_name]) I can see it in the console, but when I console.log(object) the dynamic property doesn't show.

here is the code, the property in question is teachers_matieres in the element object. PS: I console logged the property (explicitly) in each step of the code, even just before the return, it shows. But when I try to print the object it doesn't show, neither in post man.

router.get('/get-all-messages', async function (req, res, next) {
  let children = [];
  const parent = await Parent.findOne({ _id: req.query.user_id });
  const students = await Student.find({ parentPersonalId: parent.personalID });
  for (let i = 0; i < students.length; i++) {
    var element = students[i];
    element['teachers_matieres'] = [0];
    const inscription = await Inscription.findOne({ studentID: element._id });
    const theClass = await Classe.findOne({ _id: inscription.classeID });
    const schedule = await Schedule.findOne({ classeID: theClass._id });
    for (let i = 0; i < schedule.teacherID.length; i++) {
    if( schedule.teacherID[i]==null)
        continue
      const tuple = [
        await Teacher.findOne({ _id: schedule.teacherID[i] }),
        await Matiere.findOne({ _id: schedule.matierID[i] }),
      ];
      // if (!tuple in element['teachers_matieres']){
        console.log(element['teachers_matieres'].push(tuple));
      // }
    }
    //director selection
    const director = await Director.find({_id:inscription.directeurID})
    element['director'] = director
    const annexe = await Annex.find({_id:director.annexID})
    const scholar = await ScholarGroup.find({_id:annexe.scholarGroupID})
    const ceo = scholar.ceo
    children.push(element);
  }
  const msgs = await Messagerie.find().or([
    { senderID: parent._id},
    { receiverID: parent._id ,
    'approved.isApproved':true},
  ]);
  return res.json({
    error: false,
    message: 'success',
    data: { children: children, messages: msgs },
  });
});

This is the output of postman:

{
"error": false,
"message": "success",
"data": {
    "children": [
        {
            "localisation": {
                "payer": "medea",
                "wilaya": "medea",
                "daira": "medea",
                "commune": "medea"
            },
            "authentication": {
                "code": "uhB9Y",
                "expired": false
            },
            "tokens": [],
            "unreadNotices": [],
            "absence": [],
            "inbox": [],
            "msgSent": [],
            "paymentTypes": [
                "5f6a1749ddcfde4f3b0ebaf4"
            ],
            "_id": "5f68a2ec489f029205bdaa42",
            "firstNameFr": "abdou",
            "lastNameFr": "moumen",
            "firstNameAr": "moumen",
            "lastNameAr": "بن احمدي",
            "parentPersonalId": "dddd",
            "birthday": "NaN-NaN-NaN",
            "inscriptionNbr": "101",
            "image": "",
            "state": false,
            "systemscolaire": "Interne",
            "__v": 0
        }
    ],
    "messages": [
        {
            "approved": {
                "isApproved": true,
                "date": "21-9-2020",
                "time": "17:22:4"
            },
            "fileUrl": [
                {
                    "fieldname": "file",
                    "originalname": "cccc.pdf",
                    "encoding": "7bit",
                    "mimetype": "application/pdf",
                    "destination": "/home/admin/assets/schools/eco1/5f6899c86f84e38b88e270c0/messagesFiles",
                    "filename": "21-9-2020_cccc.pdf",
                    "path": "/home/admin/assets/schools/eco1/5f6899c86f84e38b88e270c0/messagesFiles/21-9-2020_cccc.pdf",
                    "size": 237233
                }
            ],
            "_id": "5f68dfae6a7b33b1c7b1f688",
            "senderID": "5f68a354489f029205bdaa45",
            "receiverID": "5f68a2d5cff2d591af390281",
            "subject": "teacher ver parent",
            "description": "<p>teacher ver parent</p>\n",
            "date": "21-9-2020",
            "time": "17:15:26",
            "__v": 0
        },
        {
            "approved": {
                "isApproved": true,
                "date": "22-9-2020",
                "time": "10:53:39"
            },
            "fileUrl": [
                {
                    "fieldname": "file",
                    "originalname": "NoticeSendReceive.js",
                    "encoding": "7bit",
                    "mimetype": "text/javascript",
                    "destination": "/home/admin/assets/schools/eco1/5f6899c86f84e38b88e270c0/messagesFiles",
                    "filename": "21-9-2020_NoticeSendReceive.js",
                    "path": "/home/admin/assets/schools/eco1/5f6899c86f84e38b88e270c0/messagesFiles/21-9-2020_NoticeSendReceive.js",
                    "size": 25393
                }
            ],
            "_id": "5f68e2174ce23cb39a7b9d22",
            "senderID": "5f68a354489f029205bdaa45",
            "receiverID": "5f68a2d5cff2d591af390281",
            "subject": "teacher ver parent",
            "description": "<p>message</p>\n",
            "date": "21-9-2020",
            "time": "17:25:43",
            "__v": 0
        }
    ]
}
}

I really need to append that property to each element, how can I do that? what's wrong with the dynamic property?

score 0 · Answer 1 · answered Sep 22 '20 at 19:57

0

If you are using something like Sequelize to get objects from a DB then you should turn them into plain objects before adding some properties. For instance, in Sequelize you should call get({ plain: true }) for each fetched objects.

const inscription = await Inscription.findOne({ studentID: element._id });
const plainInscription = inscription.get({ plain: true })
plainInscription[teachers_matieres] = // something
console.log(plainInscription) // now you can see your prop

answered Sep 22 '20 at 19:57

Anatoly

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i'm using mongoose, does it use sequelize? – Simou Sep 23 '20 at 05:28
No this is ORM-package like Sequelize but I suppose in case of Mongoose you also have model objects and not plain objects. You somehow should extract plain objects from model objects. – Anatoly Sep 23 '20 at 17:07

score 0 · Accepted Answer · answered Sep 26 '20 at 10:25

The problem was that the objects returned from mongoose inherit from document, and they are not plain JSON objects, they use .toObject() method to obtain the json object. what i had to do was add .lean() in the query like so Model.findOne().lean().exec() it tells mongoose to return a plain json object.

reference: similar question

JavaScript: dynamic property not showing unless accessed explicitly

2 Answers2