can't update DB using put request in express.js - mongodb

Question

I'm trying to update the languages_known through post request to the mongodb collection using the body of the request but its not updating i'm newbie any help would be really appreciated.
mongodb document :
{
"_id": {
"$oid": "5d63e81c342987154cdc698e"
},
"name": "anjana",
"email": "anju#gmail.com",
"age": "22",
"languages_known": [
"Bengali",
"Kannada"
],
"phone": "684684684846"
}
server code :
app.put('/students/add',function(req,res){
var myobj={
$set:{_id:require('mongodb').ObjectID(req.body.id),languages_known:req.body.remove}
}
db.collection('students').updateOne({languages_known:req.body.add},myobj,function(err,result){
if(err){throw err}
console.log("updated")
})
})
request body :
{
"id":"5d63e81c342987154cdc698e",
"remove": ["Bengali", "Kannada"],
"add": ["Tamil", "Punjabi"]
}
I've expected to update the languages_known field using this req through postman to this id

Answer 1

Ok this issue is with the query, you can't update _id of a document like that, also as your requirement is not to do that, Please try this :
server code :
// replace languages_known with new languages based on _id, in case if you wanted to update the array you can use $push
app.put('/students/add', function (req, res) {
const id = require('mongodb').ObjectID(req.body.id)
let updateQuery = {
$set: { languages_known: req.body.add }
}
db.collection('students').updateOne({ _id: id }, updateQuery, function (err, result) {
if (err) { throw err }
console.log("updated")
})
})