mongoose #set and $unset conditional - node.js

Question

in my project i want to allow optional fields in a document, but i don't want to save any null values, i.e. i want to remove any field with null.
the values can be changed during run time.
i found how i can make a field null if the user didn't send data to update it (all the fields that the user send empty values for should get deleted).
if the user send firstName/lastName as an empty string in the form i want to remove them.
await Employee.findOneAndUpdate({ _id: employee._id },
{$set: {firstName: null, lastName: null, ...req.body.newEmployee}}, { new: true, upsert: false });
i tried to add an $unset option but i got an error
MongoError: Updating the path 'firstName' would create a conflict at 'firstName'
i thought about deleting it after the update (as a second command) but i can't find a way to tell/get all the null fields of the employee, and i can't get a fixed values to check because there are many combination for the null/not null values, especially if there will be more fields in the future.
i.e. i cant tell if (FN: null, LN: null or FN: "johny", LN: null etc..)

Answer 1

Update : In case if you need to keep some fields as is in existing document then try this, with this new code only the fields coming in request will either be updated or deleted doesn't alter other existing fields in document :
Your node.js code :
let removeObj = {}
Object.entries(req.body).forEach(([key, val]) => {
if (!val) { delete req[body][key]; removeObj[key] = '' };
})
let bulkArr = []
if (req.body) bulkArr.push({
updateOne: {
"filter": { "_id": ObjectId("5e02da86400289966e8ffa4f") },
"update": { $set: req.body }
}
})
if (Object.entries(removeObj).length > 0 && removeObj.constructor === Object) bulkArr.push({
updateOne: {
"filter": { "_id": ObjectId("5e02da86400289966e8ffa4f") },
"update": { $unset: removeObj }
}
})
// For mongoDB4.2 removeObj has to be an array of strings(field names)
let removeObj = []
Object.entries(req.body).forEach(([key, val]) => {
if (!val) { delete req[body][key]; removeObj.push(key) };
})
// After this, Similar to above you need to write code to exclude empty removeObj for 4.2 as well.
Query :: On mongoDB version >= 3.2 to < 4.2 .bulkWrite():
db.yourCollectionName.bulkWrite(bulkArr)
Query :: From mongoDB version 4.2 .updateOne accepts aggregation pipeline :
db.yourCollectionName.updateOne(
{ "_id": ObjectId("5e02da86400289966e8ffa4f") },
[
{
$set: req.body
},
{ $unset: removeObj }
]
)
Old Answer : You need to try .findOneAndReplace() , if you want entire doc to be replaced :
db.yourCollectionName.findOneAndReplace({_id: ObjectId("5e02da86400289966e8ffa4f")},inputObj, {returnNewDocument:true})
Your collection :
{
"_id" : ObjectId("5e02da86400289966e8ffa4f"),
"firstName" : "noName",
"lastName": 'noName',
"value" : 1.0,
"empDept": 'general',
"password":'something'
}
Your request object is like :
req.body = {
firstName: 'firstName',
lastName: null,
value : 1.0,
empDept: ''
}
your node.js code (Removes all falsy values ( "", 0, false, null, undefined )) :
let inputObj = Object.entries(req.body).reduce((a,[k,v]) => (v ? {...a, [k]:v} : a), {})
your collection after operation :
{
"_id" : ObjectId("5e02da86400289966e8ffa4f"),
"firstName" : "firstName",
"value" : 1.0,
}
your collection after operation as per updated answer :
{
"_id" : ObjectId("5e02da86400289966e8ffa4f"),
"firstName" : "firstName",
"value" : 1.0,
"password":'something'
}