node.js - How to check if NESTED array item already exists before adding to array -

i'm creating , assigning new object id nested array item in mongo, working great. can't figure out how check against object id verify doesn't exist.

here route:

router.post('/events', function(req,res){     var loggedinuser = req.user.username;     var objectid = new objectid();      user.update(         {"username" : loggedinuser},         {             $push:{                 primaryevents:{                     _id: objectid,                     name: req.body.name,                     date: req.body.date,                     description: req.body.description                 }             }         },         {upsert:true},         function(err){             console.log('made calback');             if(err)                 res.send(err);             res.render('index', {                 user: req.user,                 primaryevents: req.user.primaryevents             });         }     ); }); 

you want check there no value in array $ne inequality operator:

        user.update(             {                  "username" : loggedinuser,                 "primaryevents._id": { "$ne": objectid }             },             {             $push:{                 primaryevents:{                     _id: objectid,                     name: req.body.name,                     date: req.body.date,                     description: req.body.description                 }             }             },             {upsert:true},             function(err){                 console.log('made calback');                 if(err)                     res.send(err);                 res.render('index', {                      user: req.user,                     primaryevents: req.user.primaryevents                 });             }         ); 

that check named properties of sub-documents in array , make sure value not exist.

so "query" portion control that. if there _id value there no match , therefore no update.

otherwise work off of else consider unique if not know _id value, "name":

        user.update(             {                  "username" : loggedinuser,                 "primaryevents.name": { "$ne": req.body.name }             },             {             $push:{                 primaryevents:{                     _id: objectid,                     name: req.body.name,                     date: req.body.date,                     description: req.body.description                 }             }             },             {upsert:true},             function(err){                 console.log('made calback');                 if(err)                     res.send(err);                 res.render('index', {                      user: req.user,                     primaryevents: req.user.primaryevents                 });             }         );