How to get one document in mongodb? source: mongoShell: https://www.udemy.com/mongodb-the-complete-developers-guide/learn/v4/t/lecture/11739212?start=34 mongoDriverNode: http://mongodb.github.io/node-mongodb-native/3.1/api/Collection.html#findOne

get_one_document_mongo_driver.js

.collection('collectionName').findOne({key:value})
// Example
const db = require('../db')
const ObjectId = require('mongodb').ObjectId

exports.getUser = ((req, res) => {
  console.log('getUser')
  filter = {
    _id: new ObjectId(req.params.userId)
  }
  db.getDb()
    .db()
    .collection('usersToSendEmail')
    .findOne(filter)
    .then((doc) => {
      res.status(200).json({doc})
    })
    .catch((error)=>{
      console.log(error)
    })
})

get_one_document_mongo_shell.js

db.collectionName.find({key:value})

// Example
> db.usersToSendEmail.find({_id: ObjectId("5c405972f3d33522c6242d31")})