Mongoose collection is not getting updated - node.js

Question

I am trying to update mongoose collection name counter.
But it's not getting updated.
counter collection
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var counterSchema = new Schema({
_id: {type: String, required: true},
sequence_value: {type: Number, default: 1}
});
var Counter = module.exports = mongoose.model('Counter', counterSchema);
API
router.post('/increment',function(req, res, next){
console.log('Sequence Counter::' + getNextSequenceValue("productId"));
)};
getNextSequenceValue Method
function getNextSequenceValue(sequenceName){
var sequenceDocument = Counters.findOneAndUpdate({
query:{_id: sequenceName },
update: {$inc:{sequence_value:1}},
new:true,
upsert: true
});
console.log('Counter value::' + sequenceDocument.sequence_value);
return sequenceDocument.sequence_value;
}
But every time I hit /increment API, console.log is printing undefined.

Answer 1

You will always get undefined since sequenceDocument is a Promise which will later resolve with the updated document if the update operation is successful or will reject with an error if it is not. In your case the console.log statement will run before the database operation has completed. This is because findOneAndUpdate is an asynchronous operation which returns a Promise object.
The update probably fails because you are passing arguments to findOneAndUpdate in an improper manner. The function accepts the query as first argument, update operation as second and query options as third argument.
You can rewrite the getNextSequenceValue in the following way:
function getNextSequenceValue(sequenceName) {
return Counters.findOneAndUpdate(
{ // query
_id: sequenceName
},
{ $inc: { sequence_value: 1 } }, // update operation
{ // update operation options
new: true,
upsert: true
}
).then(sequenceDocument => sequenceDocument.sequence_value)
}
It will now return a Promise which will resolve with the sequence value. You can use it in your controller like this:
router.post('/increment', function(req, res, next) {
getNextSequenceValue('productId')
.then(sequenceValue => {
console.log(sequenceValue)
})
.catch(error => {
// handle possible MongoDB errors here
console.log(error)
})
})