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(Javascript Node.js) How to get varibles from a IIFE

Please see my code below:
I am trying to assign the recordset to a variable, can use index.js to call this variable out.
I am able to console.log the recordset. But when I call this IIFE, it is always says undefined.
var mssql = require('mssql');
var dbcon = require('./dbcon');
var storage = (function () {
var connection = new mssql.Connection(dbcon);
var request = new mssql.Request(connection);
connection.connect(function (recordset) {
request.query('select getdate()', function (err, recordset) {
console.dir(recordset);
});
connection.close();
});
})();
module.exports = storage;
index.js
var storage = require('./storage');
"AMAZON.HelpIntent": function (intent, session, response) {
storage(function (recordset){
var speechOutput = 'Your result is '+recordset;
response.ask(speechOutput);
});
However, I can't get the recordset. I got "Your result is {object, object}. "

that's because the IIFE is executing right away, try returning a function instead and then executing that function when you import that module,
var storage = (function(mssql, dbcon) {
return function() {
var connection = new mssql.Connection(dbcon);
var request = new mssql.Request(connection);
connection.connect(function(recordset) {
request.query('select getdate()', function(err, recordset) {
console.dir(recordset);
});
connection.close();
});
}
})(mssql, dbcon);
and I don't understand why you need the IIFE, why don't you just assign the function to the variable?
If you're trying to assign the variable "recordset" to "storage" then this will never work as "connection.connect" is an asynchronous function, and in that case you should think about callback functions or promises.
Update
Based on your request, here's an implementation with a callback function and how it's used
var mssql = require('mssql');
var dbcon = require('./dbcon');
var storage = function(callback) {
var connection = new mssql.Connection(dbcon);
var request = new mssql.Request(connection);
connection.connect(function(recordset) {
request.query('select getdate()', function(err, recordset) {
if(!err && callback){
callback(recordset);
}
connection.close();
});
});
}
module.exports = storage;
// --------------------------------------------------
// implementation in another module
var storage = require("module_path"); // (1)
var answer;
storage(function(recordset){ // (2)
answer = recordset;
console.log(answer); // actual data, (3)
// implement your logic here
});
console.log(answer); // undefined (4)
// --------------------------------------------------
How this code works:
- You start by calling the storage method and sending it a callback method.
- The whole point of the callback function is that you won't wait for the result, your code will actually continue working at the same time that the storage method is connecting to the database and trying to get the data, ans since db operations are much slower, line(4) will execute before line(3).
- The flow of work will be as follows:
line (1)
line (2)
line (4)
line (3) at sometime in the future when the data is retrieved from database
- To see this more clearly, try doing this at the last line,
setTimeout(function(){console.log(answer);}, 3000);
This will wait for sometime until the data comes back;

How to access MongoDB rather than JSON file

I have created a little application that implemented a JSON file as the data store. I'm trying to learn about MEAN, so I'm trying to convert it to a NODE.js app.
I have created a mongoDB importing my JSON file using mongoimport. The db is there and connected. When I put http://localhost:3000/api/characters into the browser it returns JSON for all the characters.
I have built a connection string and required it into my controller as follows...
// FROM node app characters.controller.js
var dbconn = require('../data/dbconnection.js');
var characterData = require('../data/characters.json');
module.exports.charactersGetAll = function(req, res) {
var db = dbconn.get();
var collection = db.collection('characters');
// Get the documents from the collection
// Need to use to Array() as its only a cursor if you don't
collection
.find()
.toArray(function(err, docs) {
console.log("Found characters!", docs);
res
.status(200)
.json(docs);
});
//console.log('db', db);
//console.log("GET the Characters");
//console.log(req.query);
res
.status(200)
.json(characterData);
};
module.exports.charactersGetOne = function(req, res) {
var charId = req.params.id;
var thisChar = characterData[charId];
console.log("GET characterId", charId);
res
.status(200)
.json(thisChar);
};
From the non-NODE version of the app, I call in the JSON data as follows in my main.js file:
//FROM TRADITIONAL HTML/JS application
// Get JSON and callback so JSON can be stored globally
$.getJSON('people.json', callback);
// Populate faces and names in HTML
function callback(data) {
/*optional stuff to do after success */
var $charNames = $('.char-names');
var $faceImage = $('.faces');
$.each(data, function(index, val) {
console.log("success");
/* iterate through array or object */
/* .eq() method constructs new object from one element from set */
$charNames.eq(index).text(val.name);
$faceImage.eq(index).attr('src', val.image);
//Push all JSON to array
allTheCharacters.push(val);
allTheCharactersComp.push(val);
});
}
What I want to ask is – Is there a simple way I can access the mongoDB in the non-NODE main.js file instead of using the $.getJSON method and how would I add/adapt this for the node characters.controller.js
Hopefully, I am making sense. Apologies in advance for any misunderstanding.

exported variables got undefined while functions get exported in node js

I am creating the nodejs application which uses the mongodb.
I am connecting to mongodb only once. I want to use db in all other api's so as to achieve the connection pooling.
I have following code for mongodb connectivity:
var mongodb = require('mongodb');
var MongoClient = require('mongodb').MongoClient;
var db;
var mongoUrl = "mongodb://localhost:27017/testDB";
/**
* Connects to the MongoDB Database with the provided URL
*/
exports.connect = function(callback){
if(!db){
MongoClient.connect(mongoUrl, function(err, _db){
if (err) { throw new Error('Could not connect: '+err); }
db = _db;
console.log(db);
connected = true;
console.log(connected +" is connected?");
callback(db);
});
}else{
console.log("Not connected tis time as I am already connected");
callback(db);
}
};
exports.db = db;
I am calling connect only once when server starts from app.js. Whenever other api such as signin, register get called, they should simply use db that is exported.
So my api calls will something like(please ignore the syntax error in api call :D):
var mongo = require('./mongo');
collection = mongo.db.collection("testCollection");
// Here mongo.db id undefined
collection.findOne({"name":"John"}, function(err, result){
// Do your stuff with result here
});
From other stackoverflow posts, I tried something like in mongo.js as
module.export{
db: db,
connect : function(callback){
//function code goes here
}
}
But still I am getting the undefined for mongo.db
How would I access mongo.db in my other files?
Thanks

The reason this happens is, because connect overwrites db in the module. The exports.db=db; is not executed after calling your connect function, but on execution of the module import.
So, when you call connect, db is set to another variable, but that is not exposed outside.
Didn't do much JS lately, but this should do it:
module.exports = new mongobj();
function mongobj() {
this.db = null;
this.connect = function(callback) { /* your connect code set mongobj.db */
this.db = /* new value */ ;
}
}
When you import the module, you get the object. Accessing the objects db property will always expose the latest db value set by the connect function of the module.
var mongo = require('yourmodule');
// mongo.db is null
mongo.connect(some callback);
// mongo.db is set

This connection add in main script file...
var mongodb = require('mongodb');
var mongodb = require('mongodb');
var MongoClient = require('mongodb').MongoClient;
var mongoUrl = "mongodb://localhost:27017/testDB";
ObjectId = module.exports = require("mongojs").ObjectId;
MongoClient.connect(mongoUrl, function(err, database){
if(err){
console.log("mongodb error >>"+err);
} else {
db = module.exports = database;
}});
db.collection('game_users').findOne({_id:ObjectId("123456789")},function(err, data) {});

define an object:
var db = {__db: undefined}
and then:
exports.db = db
const db = require('./mongo').db.__db

node.js never exits after insert to couchbase, opposite of most node questions

My problem seems to be the opposite of every node.js question :-) I have a simple forEach loop to read a list of files and insert them into a Couchbase database. This works great, but it never exits after reading all the lines. So I added a counter to shutdown the couchbase connection after all inserts are complete. This works.
This process is intended to load hundreds of thousands of files, so I brought the async module into the mix to batch the inserts into groups of 100. The async.eachLimit is used to iterate over the array and insert documents in batches. Now the orig problem is back. Whatever magic async.eachLimit uses to recognize the process is complete is not happening.
I've been going through javascript scoping, callbacks, async, etc. Google searches are hitting keywords but not this issue. I've reduced the code down to the following testcase. To test, create three files and add their names to testlist.txt.
The async.eachLimit in place works up until it hits the limit, then hangs. Comment this out and uncomment array.forEach line and it works. Thanks in advance!
var fs = require('fs');
var couchbase = require('couchbase');
var async = require('async');
var filelist = 'testlist.txt';
var key_count = 0;
var cb_config = { host: 'localhost:8091', bucket: 'default'};
var db = new couchbase.Connection(cb_config, function(err) {
if (err) {
console.log('ERRR connect to couchbase at config['+cb_config+']');
throw err;
}
});
var insertFile=function(line) {
console.log('LOAD ['+line+']');
fs.readFile(line, function(file_err, f_doc) {
if(file_err) throw file_err;
db.set(line, f_doc, function(db_err, db_res){
if (db_err) {
console.log('FAIL ['+line+'] err['+db_err+']');
} else {
console.log('PASS ['+line+']');
}
key_count--;
if (key_count == 0) {
console.log('DONE Shutting down client, no more keys');
db.shutdown();
}
});
});
}
// read list of files into data array from file filelist
fs.readFile(filelist, function(filelist_err, lines) {
if(filelist_err) throw filelist_err;
// HACK split adds empty line to array, use replace to fix
var array = lines.toString().replace(/\n$/, '').split('\n');
key_count = array.length;
console.log('INIT lines['+key_count+']');
async.eachLimit(array, 2, insertFile, function(err) { console.log('FAIL async err['+err+']');} );
//array.forEach(function(data){insertFile(data);return;});
});
Testcase output using array.forEach:
INIT lines[3]
LOAD [files.big.txt]
LOAD [files.little.txt]
LOAD [files.txt]
PASS [files.little.txt]
PASS [files.big.txt]
PASS [files.txt]
DONE Shutting down client, no more keys
Testcase output using async.eachLimit:
INIT lines[3]
LOAD [files.big.txt]
LOAD [files.little.txt]
PASS [files.little.txt]
PASS [files.big.txt]
... hang, never gets to 3...

After review with a coworker, they spotted my mistake. I missed the async callback in my insertFile function. Adding that in works and allows me to remove the key counter! Solution code below:
var fs = require('fs');
var couchbase = require('couchbase');
var async = require('async');
var filelist = 'testlist.txt';
var key_count = 0;
var cb_config = { host: 'localhost:8091', bucket: 'default'};
var db = new couchbase.Connection(cb_config, function(err) {
if (err) {
console.log('ERRR connect to couchbase at config['+cb_config+']');
throw err;
}
});
var insertFile=function(line, callback) {
console.log('LOAD ['+line+']');
fs.readFile(line, function(file_err, f_doc) {
if(file_err) throw file_err;
db.set(line, f_doc, function(db_err, db_res){
if (db_err) {
console.log('FAIL ['+line+'] err['+db_err+']');
callback(db_err);
} else {
console.log('PASS ['+line+']');
callback();
}
});
});
}
// read list of files into data array from file filelist
fs.readFile(filelist, function(filelist_err, data) {
if(filelist_err) throw filelist_err;
// HACK stoopid bug split adds empty line to array, use replace to fix
var array = data.toString().replace(/\n$/, '').split('\n');
key_count = array.length;
console.log('READ files['+key_count+']');
async.eachLimit(array, 2, insertFile, function(err) {
if (err) console.log('LAST with async err['+err+']');
console.log('DONE Shutting down client, no more keys');
db.shutdown();
});
});
And successful output:
$ node testcase.js
READ files[3]
LOAD [files.big.txt]
LOAD [files.little.txt]
PASS [files.little.txt]
LOAD [files.txt]
PASS [files.big.txt]
PASS [files.txt]
DONE Shutting down client, no more keys

How to create a user model with node.js?

I'd like to create a model to handle everything related to users, starting with a findOne() function.
app.js:
var u = new User(client);
u.findOne(function(error, user) {
console.log(error, user);
});
models/User.js:
var User = function (client) {
this.client = client
};
User.prototype.findOne = function (id, callback) {
client.connect();
client.get('testkey', function(error, result) {
var test = "hello#world.com";
callback(null, test);
client.close();
});
};
module.exports = User;
node.js complains findOne() would be undefined.
What's the correct way of creating such models and providing them with objects, like database pools etc.?

Your code contains various errors:
You do not use new when creating the instance
You mixed a function with the object literal syntax:
var User = function (client) {
client: client
};
You want this.client = client; instead. Right now the function body does nothing as it just defines a label called client does nothing with the variable client.
I would suggest you to search for an existing ORM for node.js instead of trying to write one on your own.