Mongoose: $inc not working - node.js

Question

I am not sure what the problem is, as I've read numerous examples.
Taken from what I was advised here in this StackOverFlow(Mongoose - Increment a value inside an array of objects), I changed the format of poll at ease to accommodate what was recommended.
So I was able to create a document format as so:
{
"_id": "584c4160b3b22e1bdad59bce",
"title": "Food",
"description": "test",
"labelOptions": {
"burger": 29,
"coffee": 44,
"pizza": 23
},
"date": "Dec 10, 2016",
"__v": 0
}
Here's what I have so far:
Poll Model
const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const pollData = new Schema({
title: String,
description: String,
labelOptions: {},
date: String
})
module.exports = mongoose.model('PollData', pollData)
Using express and mongoose, here's what I have:
app.put('/polls/:id', function(req, res){
let id = req.params.id;
let labelOption = req.query.labelOption;
let query = `labelOptions.${labelOption}`
Poll.findByIdAndUpdate(
id,
{$inc: { query: 1 } },
function(err, document){
console.log(err)
console.log(document)
}
)
})
In my terminal, I see that console.log(document it receives the document I was looking for but it does not update the value at all.
Am I setting up the Model correctly? Or does Mongoose does not support template strings?
***update
This is snippet of how I am creating documents
let labelOptions = {}; <=== creating object literal to hold as placeholder
const title = req.body.title;
const description = req.body.description;
req.body.labelOptions.split(/,\s*/).map( prop =>{
labelOptions[prop] = 0 // set counter to default 0
})
const poll = new Poll({
title: title,
description: description,
labelOptions: labelOptions,
date: moment().format('MMM D, YYYY')
});
poll.save(function(err) {
if (err) { return next(err); }
res.json({ message : 'Poll added!'})
});

Answer 1

After doing some research across the internet, I found the reason why it wasnt working: You can't initialize objects with 'dynamic' keys.
Source: Mongoose update on a string variable not working?
By knowing that, it was just a simple solution to initialize an literal object as so:
let id = req.params.id;
let labelOption = req.query.labelOption;
let query = "labelOptions." + labelOption
let obj = {
[query] : 1
}
Poll.findByIdAndUpdate(
id,
{$inc: obj },
function(err, document){
console.log(err)
console.log(document)
}
)