How sort results in a nodejs - mongodb search, but, by calling a dynamic method

I'm developing a web app in nodejs connected to mongodb via mongo native connector.

In one of my js files, I have a generic method to invoke a "find" or "findOne" operation to retrieve whatever I need from a mongodb collection, like this:

It works fine for me.

But now, I need to sort the results, and as far as I know, Mongodb use the "sort" method to achieve this.

collection.ensureIndex(indexedFields, function(error, indexName) {
    if (error) {
        callback(error);
    } else {
        var operation = (params.options.one) ? collection.findOne : collection.find;

        operation.call(collection, params.selector, params.fields, params.options,
            function(error, result){
                if (error) {
                    ...
                } else {
                    ... 
                }       
            }
        );
    }
});

In an simple query, this should be like this: For example:

collection.find().sort({field : 1}),

I don't know how to call "sort" method, doing it im my generic way.

Any ideas?

Thanks.