Access MongoDB nested object using variables

Using the npm package mongojs, I need to access nested objects using a variable. The following, however, does not work:

    let userID = req.user._id,
        marketName = req.body.marketName,
        itemName = req.body.item.itemName,
        crossOff = req.body.item.isCrossed;

    markets.updateOne(
       {
        _id: userID,
        "marketList.marketName": marketName
      },
      {$set : {`marketList.$.shoppingList.${itemName}.isCrossed`: crossOff}},
      (err, doc) => {
        if(err) { res.status(400).send('Bad Request') }
        else { res.status(204) }
        res.end();
      });
   });

As you cannot use template strings in this situation, hence the unexpected template string error.

I am aware that it is possible to use bracket-notation to use a variable as a key, however, this will not help my situation since I am unable to set a variable with the entire key stored in it as a string.

What are my options?

via Shadow