javascript - Aggregation working in console but not node? -

i totally new node.js (and javascript too), idea of anonymous functions, callbacks , likes totally foreign me , i'm still wrapping head around all... said please go easy on me! :)

i've got following query i'm able use in mongo console without issues:

db.warmod_events.aggregate({ $match: {     $and: [         { "match.id": 1 },         { "match.event.player.name": 'xxx' },         { "match.event.event": 'round_stats' }     ] } }, { $group: { _id : null, kills : { $sum: "$match.kills" } } }); 

from reading mongo node driver documentation (which seems little brief) came with, reason never returns anything, query result empty , i'm not sure why?

var getkills = function (db, callback) {   var collection = db.collection('warmod_events');   collection.aggregate(       [         {           $match: {             and: [               {"match.matchid": 1},               {"match.event.player.name": 'jim'},               {"match.event.event": 'round_stats'}             ]           }         },         {           $group: {             "_id": null, kills: {$sum: "$match.kills"}           }         }       ], function (err, result) {         console.dir(result);         callback(result);       }); }; 

an example of document in collection:

{     "match": {         "event": {             "timestamp": "2015-06-03 15:02:22",             "event": "round_stats",             "round": 1,             "player": {                 "name": "jim",                 "userid": 45,                 "uniqueid": "bot",                 "team": 2             },             "shots": 0,             "hits": 0,             "kills": 0,             "headshots": 0,             "tks": 0,             "damage": 0,             "assists": 0,             "assists_tk": 0,             "deaths": 0,             "head": 0,             "chest": 0,             "stomach": 0,             "leftarm": 0,             "rightarm": 0,             "leftleg": 0,             "rightleg": 0,             "generic": 0         },         "matchid": 1     } } 

the and in $match should $and instead:

$match: {     $and: [         {"match.matchid": 1},         {"match.event.player.name": 'jim'},         {"match.event.event": 'round_stats'}     ] } 

however, because $and terms use unique keys, don't need use $and , can simplify to:

$match: {     "match.matchid": 1,     "match.event.player.name": 'jim',     "match.event.event": 'round_stats' }