如何在Node.js中使用MongoDB聚合

var mongoose = require('mongoose');
var membersModel = require('./model_member.js');
exports.request_friend_list = function(req, res){
var userid=req.body.userid;
console.log(userid);

//  membersModel.find({_id: userid,friends:{status:0}},{_id:0,'friends':1,},function(err,data)
    membersModel.aggregate(
         {$match: {_id:userid}},
         {$project: {friends: 1}},
         {$unwind: "$friends"},
         {$match: {"friends.status": 0}}
     ,function(err,data){
     if(err){
        res.json({status:"error"});
        throw err;
    }else{
        if(JSON.stringify(data).length > 0){
            console.log(JSON.stringify(data));
            res.json(data);
        }
        else{
            res.json({status: "Data is not Exist."});
            console.log("Data is not Exist.");
        }
    }   
});
var mongoose = require('mongoose');
var members