Updating fields in array -NodeJs - node.js

Question

I have this code that loop through all users in DB then look for specific events based on the id value and if there is a match it should update the field caption with a new given data,
for the code :
1- search all potential user = OK
2 - search and find events based on id = OK
3- update the field caption = NOK
this is my code hope I mentioned everything
router.post('/delete/:id',async (req, res) => {
const eventId = req.params.id // this is the ID of the event
User.find({}).lean(true).exec((err, users) => {
let getTEvent = [];
for (let i = 0; i < users.length; i++) {
if (users[i].events && users[i].events.length) {
for (let j = 0; j < users[i].events.length; j++) {
if (users[i].events[j]._id === eventId) {
console.log('you event is :'+ eventId) // this statement to verify if really got the correct ID or not
users[i].events[j].caption ="deleted" // from here the problem
users[i].save(err => {
if (err) throw err;
console.log("status changed saved");
// Redirect back after the job is done.
});
}
}
}
}
});
})
the error that I get is that users[i].save is not a function I don't know with what should I replace it,
As per comments #whoami
router.post('/delete/:id', (req, res) =>
User.findOneAndUpdate({
"events._id": req.params.id
},
{ $set: { "events.caption": "yesssss" }
}, {upsert: true}, (err, user) => {
if (err) {
res.send('error updating ');
} else {
console.log(user);
console.log(req.params.id)
}
}));
Below the mongoDb and event datastructure
Hope I clarified everything ,
Best Regards,

Answer 1

Actual Issue :
.save() works on mongoose document but not on javaScript object. In your code you've already converted mongoose documents returned from .find() call to .Js objects using : .lean(true).
.lean(true) is used to convert mongoose docs to .Js objects to work manipulate fields inside docs in code.
Fixing code :
const mongoose = require('mongoose');
router.post("/delete/:id", async (req, res) => {
const eventId = req.params.id; // this is the ID of the event
await User.find({})
.lean(true)
.exec((err, users) => {
let getTEvent = [];
for (let i = 0; i < users.length; i++) {
if (users[i].events && users[i].events.length) {
for (let j = 0; j < users[i].events.length; j++) {
if (users[i].events[j]._id === eventId) {
console.log("you event is :" + eventId);
users[i].events[j].caption = "deleted";
users[i]._id = mongoose.Types.ObjectId(users[i]._id); // Converting `_id` string to `ObjectId()` to match with type of `_id` in DB
let user = new User(users[i]); // Create a mongoose doc out of model
user.save((err) => { // As we're passing `_id` in doc to `.save()` it will be an update call rather-than insert
if (err) throw err;
console.log("status changed saved");
// Redirect back after the job is done.
});
}
}
}
}
});
});
As I've mentioned this can be done with out this extra process of reading docs/iteration/update call. Using .updateOne() or .updateMany() along with $ positional operator things can be done in one DB call :
const mongoose = require('mongoose');
router.post("/delete/:id", async (req, res) => {
const eventId = req.params.id; // this is the ID of the event
/** We're using `.updateMany` with filter on `events._id` -
* So that all user docs which has `'events._id': eventId` will be updated,
* If you've a particular user needs to be updated used `.updateOne()` with a filter to find that user document - filter kind of `userName`
*
* Both `.updateMany()` or `.update()` will return write result but not the docs,
* if you need docs in response use `.findOneAndUpdate` or `.findAndModify()`
*/
/** `$` helps to update particular object's caption field in `events` array (Object where `{ 'events._id': eventId }` ) */
await User.updateMany({ 'events._id': eventId },{$set : {'events.$.caption': 'deleted'}}).exec((err)=>{
if (err) throw err;
console.log("status changed saved");
// Redirect back after the job is done.
})
});
Ref : update-documents