MongoDB mongoose向数组添加数据

我正试图通过mongoose的post请求将数据添加到数组中。我可以用Model.find()找到正确的数据。但我不知道如何在每个post请求上向“guests”数组添加数据。例如,我希望来宾返回这样的内容(可以在post请求中添加来宾):

guests: [{
    id: 12412,
    naam: 'John',
    email: 'john@doe.com'
  },
  {
    id: 12412,
    naam: 'John',
    email: 'john@doe.com'
  }
]

var express = require('express');
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
const bodyParser = require("body-parser");

var app = express();

var schemaName = new Schema({
  eventid: String,
  evenementnaam: String,
  locatie: String,
  datum: String,
  tijd: String,
  beschrijving: String,
  naam: String,
  email: String,
  telefoon: String,
  image: String,
  time: Number,
  guests: [{
    userid: Number,
    naam: String,
    email: String
  }] // WANT TO ADD TO THIS ARRAY

}, {
  collection: 'evenementen'
});

var Model = mongoose.model('Model', schemaName);

mongoose.connect('mongodb+srv://db');

app.post('/addguest', function(req, res) {

  req.body.eventid;

  mongoose.connection.on('open', function(err, doc) {
    console.log("connection established");

    mongoose.connection.db.collection('evenementen', function(err, docs) {

      Model.find({
        'eventid': req.body.eventid;
      }, function(err, result) {
        if (err) throw err;
        if (result) {
          // ADD GUEST TO GUESTS ARRAY
        } else {
          res.send(JSON.stringify({
            error: 'Error'
          }))

        }
      })


    });
  });
});

更新#1 下面的测试没有给“guests”添加任何内容

mongoose.connection.on('open', function (err, doc) {
console.log("connection established");

var newdata = [{
    userid: 21424,
    naam: 'John Test',
    email: 'test@test.com'
}];

mongoose.connection.db.collection('evenementen', function (err, docs) {

    Model.findOne({
        'eventid': 'srA4aqC'
    }, function (err, result) {
        if (err) throw err;
        if (result) {
            console.log(result);
            Model.update({
                'eventid': 'srA4aqC'
            }, {
                '$push': {
                    'guests': {
                        '$each': newdata
                    }
                }
            })
            console.log('succes');
        } else {
            res.send(JSON.stringify({
                error: 'Error'
            }))

        }
    })


});
});

需要从几个元素中删除''。正确代码:

$push: {
    guests: {
          $each: newdata
        }
}