$push is duplicated when querying findOneAndUpdate in mongoose, what's wrong?

Question

MongoDB

When trying to add data to the database, $push for some reason duplicates them in the field, i.e. the field with an array called dates in the database should eventually have 21 array elements after sending the data, but in fact there are 42 of them. The data is duplicated.

Database request code:

router.post('/set-new-activities', async (req, res) => {
  const { id, activities } = req.body;

  console.log(id);
  console.log(activities);

  await UserCalendar.findOneAndUpdate(
    { _id: new ObjectId(req.session.userId), actions: { $elemMatch: { _id: id } } },
    { $push: { 'actions.$.dates': activities } },
    (err) => {
      if (err) throw err;

      console.log('success');

      res.json('success');
    },
  );
});

Scheme:

const { Schema, model } = require('mongoose');

const schema = new Schema({
  name: {
    type: String,
    required: true,
  },
  password: {
    type: String,
    required: true,
  },
  actions: [{
    name: { type: String },
    days: [],
    debt: { type: Boolean, default: false },
    created: { type: Date, default: '2020-03-16' },
    status: { type: Boolean, default: true },
    dates: [{
      year: { type: String },
      month: { type: String },
      day: { type: String },
      status: { type: Boolean, default: false },
    }],
  }],
});

POST request code to the server:

const obj = {
        id: action._id,
        activities: newActivity,
      };

      const response = await fetch('/set-new-activities', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json;charset=utf-8',
        },
        body: JSON.stringify(obj),
      });

      if (response.ok) {
        console.log('Активность обновлена');
      } else {
        throw new Error(Возникла проблема с fetch запросом. ${response.status});
      }

Here's what we end up with in the database:


And this is what the console.log on the server gave out:


There are no errors, and the object itself with the data was sent once. Perhaps I screwed up somewhere in the query to the database. because I'm just getting used to mongoose.

Answer 1

In short, instead of $push I used $addToSet and duplication stopped