I tried running my delete API but keep getting route.post requires callback function but got object undefined instead

So basically I am trying to connect my delete API to my routes.js. I have my insert, update, query as well as a login API and it all works well except when i put my delete API it comes up with this error.

Error: Route.post() requires callback functions but got a [object Undefined] at Route.(anonymous function) [as post] (C:\Users\tester01_2\myproject\node_modules\express\lib\router\route.js:202: 15)

Routes.js

var express = require('express');
var dbInsert = require('./dbInsert');
var dbQuery = require('./dbQuery');
var dbUpdate = require('./dbUpdate');
var router = express.Router();
var account = require('./account');
var dbRemove = require('./dbRemove');
//var dbImport = require('./dbImport');


router.route('/insertRecord').post(dbInsert.postCollection);
//router.route('/importrecords').post(dbImport.postCollection);
router.route('/updateRecord').post(dbUpdate.postCollection);
router.route('/queryRecord').post(dbQuery.postCollection);
router.route('/login').post(account.postCollection);
router.route('/deleteRecord').post(dbRemove.postCollection);
module.exports = router;

dbRemove.js

var MongoClient = require('mongodb').MongoClient;
var url = 'mongodb://localhost:27017/myproject';
var deleteRecord = function(db, req, callback){
db.collection('documents').updateMany({ "SAM ID" : req.body.samId}, {
    $set: {
        "Active Status" : "0"
    }
    }, function(err,results){
        if(err) return callback(err);
        console.log('Done');
        console.log(results);
        var cursor = db.collection('documents').find({
            "SAM ID" : req.body.samId
        }).toArray(function(err,doc){
            if(err)
                return callback(err);
            else {
                console.log('Succesfully deleted');
                console.log(doc);
                return callback(null, JSON.stringify(doc));
            }
        });
    }
);
};
module.exports = {
postcollection : function(req, res){
    var samId = req.body.samId;
    MongoClient.connect(url, function(err, db) {
    if(err){
        res.send(err);
        res.end();
    }
    deleteRecord(db, req, function(err, doc){
        if(err){
            res.send(err);
        } else{
            setTimeout(function(){
                res.send(doc);
                res.end();
            }, 2000);
        }
        db.close();
    });
});
}
}   

I can't seem to what went wrong in the callback functions such that it returns a object undefined because I used the same format as my other apis. Any help is appreciate, thanks!

via Ong Kong Tat