top.js

function byRating(a, b) {
        var x = a[1];
        var y = b[1];
        return y - x;
}

app.get('/top', function(req, res){
        db.keys('image:*:location', function(err,keys){
                if (err) { throw err; }
                var images = [];
                var originalCount = 0;
                var returnCount = 0;
                keys.forEach(function(key){
                        var split = String(key).split(':');
                        originalCount++;
                        db.mget('image:' + split[1] + ':location',
                                'image:' + split[1] + ':rating',
                                function(err, image){
                                        images.push(image);
                                        returnCount++;
                                        if (originalCount == returnCount) {
                                                images.sort(byRating);
                                                res.render('top.ejs', {
                                                        locals: {
                                                                images: images
                                                        }
                                                });
                                        }
                        });
                });
        });
});