update mongodb with node.js using a variable in $set

Question

I am making a voting system, the voting is done with a link. In my index.js I get the required values and put them in variables. The "type" variable stands for the field in my mongodb wich needs to be updated, I have put it in a variable because it depends on which link is clicked.

Now in the $set function they require the db field and a new value, for both I use variables but my "type" variable doesn't work. And when I go to my mongodb there is a new table created called "type". How can this be solved?

router.get('/vote/:Id/:Value/:Type', function(req, res) {
var db = req.db;
var id = req.params.Id;
var type = req.params.Type;
var value = parseInt(req.params.Value);
var newValue = value + 1;
var collection = db.get('games');

collection.update(
    {"_id" : id},
    {$set: {type: newValue}}
, function (err, doc) {
    if (err) {
        res.send("There was a problem");
    }
    else {
        res.location("../../../admin");
        res.redirect("../../../admin");
    }
});

});

Answer 1

In javascript you cannot use variables as property names in object literals, and that's what you're trying to do.

Try it:

var a = 'someProperty';

var o = {a: 'somePropertyValue'};

console.log(o);

will print { a: 'somePropertyValue' } not {someProperty:'somePropertyValue}.

If javascript permitted referencing variables in property names in object literal notation it would have to get rid of unquoted names as those would create ambiguity. Should a be used as the value of the property or should it be the value of the variable a?

Try creating the update object literal with an object crated beforehand without the usage of object literal notation, so your code looks something like this:

router.get('/vote/:Id/:Value/:Type', function(req, res) {
    var db = req.db;
    var id = req.params.Id;
    var type = req.params.Type;
    var value = parseInt(req.params.Value);
    var newValue = value + 1;
    var collection = db.get('games');

    //We create the $set property/value pair using property assignment, not the object literal
    var updateVal = {};
    updateVal[type] = newValue;

    collection.update(
        {"_id" : id},
        {$set: updateVal}   //use it here
        , function (err, doc) {
            if (err) {
                res.send("There was a problem");
            }
            else {
                res.location("../../../admin");
                res.redirect("../../../admin");
            }
        }
    );
});

Even better, construct the whole $set operation beforehand.