node.js - Mongo values not updating -

i'm trying increment value of object in mongoose , seems not want go past 2?? there i'm missing? i'm new mongo

campsite.findone({slug : req.body.campsite.slug }, function(err, site){      if(!site.tracking){         console.log("no previous tracking @ all");         site.tracking = {};     }      if(site.tracking[req.body.tracking_type] == undefined){         console.log("no previous tracking of type");         site.tracking[req.body.tracking_type] = 1;     }else{         console.log("well count then!");         site.tracking[req.body.tracking_type] += + 1;     }      site.save(function (err, fluffy) {         console.log(err);     });      res.send(200); }); 

it wont save updated result? schema below

var campsitesschema = new schema({     name: string,     address_line_1: string,     address_line_2: string,     county: string,     postcode: string,     loc: array,     website: string,     email: string,     telephone_1: string,     telephone_2: string,     description: string,     slug:string,     status:string,     confirm_url_key: string,     password: string,     short_description: string,     long_description: string,     features: array,     tracking: {} }); 

you're better off using update $inc modifier

campsite.update({slug : req.body.campsite.slug }, {$inc: { 'tracking[' + req.body.tracking_type + ']' : 1} });