Node.js - Counting the number of objects in MongoDB collection

Question

I am new to Node.js and MongoDB and I am really struggling to wrap my head around callbacks. I have read a few articles but it is still quite confusing to me. In the code below, I am trying to return the count of orders that have some properties which I have expressed in the query in orderModel.count(query, next):

controllers/order.js:

var mongoose = require ('../config/db');
var orderModel = require('../models/order').model;
var User = require('./user');
var Error = require('../config/error');
createOrder: function (user, order, next) {
  if (newOrder.totalPrice > user.credit && orderModel.
            count({$and: [{user: order.user}, {active: true}, {$or: [{status: 0}, {status: 1}]}]},
             function(err, count){
               if(err)
                console.log(err);
               else
                 count; }) > 0)
              return next({error: Error.InsufficientCredits});
}

I don't think I am correctly obtaining the variable count because when I tried printing out the result of the second condition in the if statement, I got this data printed out:

Query {
_mongooseOptions: {},


mongooseCollection: 
   NativeCollection {
     collection: Collection { s: [Object] },
     opts: { bufferCommands: true, capped: false },
     name: 'orders',
     collectionName: 'orders',
     conn: 
      NativeConnection {
        base: [Object],
        collections: [Object],
        models: [Object],
        config: [Object],
        replica: false,
        hosts: null,
        host: 'dsXXXXXX.mlab.com',
        port: XXXXXX,
        user: 'XXXX',
        pass: 'XXXX',
        name: 'X',
        options: [Object],
        otherDbs: [],
        _readyState: 1,
        _closeCalled: false,
        _hasOpened: true,
        _listening: false,
        db: [Object],
        _events: {},
        _eventsCount: 0 },
     queue: [],
     buffer: false,
     emitter: 
      EventEmitter {
        domain: null,
        _events: {},
        _eventsCount: 0,
        _maxListeners: undefined } },
....

chridam · Accepted Answer · 2016-11-03 11:23:50Z

You need to put your logic inside the Model.count() method callback function as:

var mongoose = require ('../config/db'),
    orderModel = require('../models/order').model,
    User = require('./user'),
    Error = require('../config/error');

var createOrder = function (user, order, next) {
    orderModel.count({
        "user": order.user, 
        "active": true, 
        "status": { "$in": [0, 1] }
    }, function(err, count) { //<-- put logic in this callback
        if (err) {
            console.log(err);
            throw err;
        } else if (newOrder.totalPrice > user.credit && count > 0) {
            // logic for creating order here
        } else {
            return next({ "error": Error.InsufficientCredits });
        }        
    })
}

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