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Node.js mssql return query result to ajax

I'm new to learning Node.js, so I'm still getting used to asynchronous programming and callbacks. I'm trying to insert a record into a MS SQL Server database and return the new row's ID to my view.
The mssql query is working correctly when printed to console.log. My problem is not knowing how to properly return the data.
Here is my mssql query - in addJob.js:
var config = require('../../db/config');
async function addJob(title) {
var sql = require('mssql');
const pool = new sql.ConnectionPool(config);
var conn = pool;
let sqlResult = '';
let jobID = '';
conn.connect().then(function () {
var req = new sql.Request(conn);
req.query(`INSERT INTO Jobs (Title, ActiveJD) VALUES ('${title}', 0) ; SELECT ##IDENTITY AS JobID`).then(function (result) {
jobID = result['recordset'][0]['JobID'];
conn.close();
//This prints the correct value
console.log('jobID: ' + jobID);
}).catch(function (err) {
console.log('Unable to add job: ' + err);
conn.close();
});
}).catch(function (err) {
console.log('Unable to connect to SQL: ' + err);
});
// This prints a blank
console.log('jobID second test: ' + jobID)
return jobID;
}
module.exports = addJob;
This is my front end where a modal box is taking in a string and passing it to the above query. I want it to then receive the query's returned value and redirect to another page.
// ADD NEW JOB
$("#navButton_new").on(ace.click_event, function() {
bootbox.prompt("New Job Title", function(result) {
if (result != null) {
var job = {};
job.title = result;
$.ajax({
type: 'POST',
data: JSON.stringify(job),
contentType: 'application/json',
url: 'jds/addJob',
success: function(data) {
// this just prints that data is an object. Is that because I'm returning a promise? How would I unpack that here?
console.log('in success:' + data);
// I want to use the returned value here for a page redirect
//window.location.href = "jds/edit/?jobID=" + data;
return false;
},
error: function(err){
console.log('Unable to add job: ' + err);
}
});
} else {
}
});
});
And finally here is the express router code calling the function:
const express = require('express');
//....
const app = express();
//....
app.post('/jds/addJob', function(req, res){
let dataJSON = JSON.stringify(req.body)
let parsedData = JSON.parse(dataJSON);
const addJob = require("../models/jds/addJob");
let statusResult = addJob(parsedData.title);
statusResult.then(result => {
res.send(req.body);
});
});
I've been reading up on promises and trying to figure out what needs to change here, but I'm having no luck. Can anyone provide any tips?

You need to actually return a value from your function for things to work. Due to having nested Promises you need a couple returns here. One of the core features of promises is if you return a Promise it participates in the calling Promise chain.
So change the following lines
jobID = result['recordset'][0]['JobID'];
to
return result['recordset'][0]['JobID']
and
req.query(`INSERT INTO Jobs (Title, ActiveJD) VALUES ('${title}', 0) ; SELECT ##IDENTITY AS JobID`).then(function (result) {
to
return req.query(`INSERT INTO Jobs (Title, ActiveJD) VALUES ('${title}', 0) ; SELECT ##IDENTITY AS JobID`).then(function (result) {
and
conn.connect().then(function () {
to
return conn.connect().then(function () {
You may need to move code around that is now after the return. You would also be well served moving conn.close() into a single .finally on the end of the connect chain.
I recommend writing a test that you can use to play around with things until you get it right.
const jobId = await addJob(...)
console.log(jobId)
Alternatively rewrite the code to use await instead of .then() calls.

Hashchain generating using async

I'm trying to generate a hashchain using the following code:
var async = require('async');
var _ = require('lodash');
var offset = 1e7;
var games = 1e7;
var game = games;
var serverSeed = '238asd1231hdsad123nds7a182312nbds1';
function loop(cb) {
var parallel = Math.min(game, 1000);
var inserts = _.range(parallel).map(function() {
return function(cb) {
serverSeed = genGameHash(serverSeed);
game--;
query('INSERT INTO `hash` SET `hash` = ' + pool.escape(serverSeed));
};
});
async.parallel(inserts, function(err) {
if (err) throw err;
// Clear the current line and move to the beginning.
var pct = 100 * (games - game) / games;
console.log('PROGRESS: ' + pct.toFixed(2) + '%')
if (game > 0){
loop(cb);
}else {
console.log('Done');
cb();
}
});
}
loop(function() {
console.log('Finished with SEED: ', serverSeed);
});
When I run this code it generates a hash chain of 1k hash's, while I'm trying to generate a chain of 1m hash's. It seems like async isn't working properly, but I have no idea why, there are no errors in console, nothing that points out a flaw.
Any ideas?

Do you can run it with smaller games (about 3000)?
Your parallel function nerver send done signal because the callback of inserts item never trigged. I think query function has two pramasters query(sql: string, callback?: (err, result) => void) (Typescript style).
I suggest you change your logic and flow like below block code:
var inserts = _.range(parallel).map(function() {
return function(cb) {
serverSeed = genGameHash(serverSeed);
query('INSERT INTO `hash` SET `hash` = ' + pool.escape(serverSeed), function(err, result) {
if(result && !err) {
game--;
}
cb(); // remember call the callback
});
};
});
In your code, you have used async.parallel, I think it is not good idea, too many connection has be open(1m). Recommeded for this case is parallelLimit

Two async module functions work asynchronously

I tried to scrap for thousands of pages. So I used async.timesSeries and async.waterfall. Each of functions work synchronously very well but they don't work together. What can I do?
The logic is simple.
Because I want to scrape pages are "http://udb.kr/local/category/390101?page="1~1167, async.timesSeries loop 1 to 1167
async.waterfall scraps components of pages
but messages that console shows me looks like this
info.NM values // just for explain, It shows me each attires of obj because I insert console.log(info.NM) for verifying.
info.NM values
info.NM values
info.NM values and randomly ----- page number -----
...
['done',
'done',
'done',
'done',
'done',
...
'done']
info.NM values again
.../Users/Snark/Dev/job_apply/cheerio_job_app_list.js:29
if (tObj[m+1].children != 0) {info.nAddr = tObj[m+1].firstChild.data}else{info.nAddr = null};
^
TypeError: Cannot read property 'children' of undefined
at /Users/Snark/Dev/job_apply/cheerio_job_app_list.js:29:17
at fn (/Users/Snark/node_modules/async/lib/async.js:746:34)
at /Users/Snark/node_modules/async/lib/async.js:1212:16
at /Users/Snark/node_modules/async/lib/async.js:166:37
at /Users/Snark/node_modules/async/lib/async.js:706:43
at /Users/Snark/node_modules/async/lib/async.js:167:37
at /Users/Snark/node_modules/async/lib/async.js:1208:30
at Request._callback (/Users/Snark/Dev/job_apply/cheerio_job_app_list.js:21:6)
at Request.self.callback (/Users/Snark/node_modules/request/request.js:198:22)
at emitTwo (events.js:87:13)
And this is js code.
var request = require("request"),
cheerio = require("cheerio"),
jsonfile = require("jsonfile"),
fs = require("fs"),
async = require("async");
var info = {},
dbArray = [];
var url = "http://udb.kr/local/category/390101?page=";
async.timesSeries(1166, function(n, next) {
var page = n + 1
async.waterfall([
function(callback) {
request(url + page, function(error, response, html) {
if (error) {
throw error
};
var $ = cheerio.load(html),
tObj = $('tbody tr td');
callback(null, tObj);
});
},
function(tObj, callback) {
for (var m = 0; m < 150; m = m + 5) {
if (tObj[m]) {
info.NM = tObj[m].firstChild.children[0].data
} else {
info.NM = null
};
if (tObj[m + 1].children != 0) {
info.nAddr = tObj[m + 1].firstChild.data
} else {
info.nAddr = null
};
console.log(info.NM);
dbArray.push(info);
}
callback(dbArray, callback);
},
function(dbArray, callback) {
fs.appendFile('./jobDB_l.json', JSON.stringify(dbArray), function (err) {
if (err)
throw err;
});
callback(null, 'done');
}
], function(err, result) {
console.log('----- ' +page+ '-----');
});
next(null, 'done');
}, function(err, result) {
console.log(result)
});

To get these to work together where you are using waterfall inside of each timesSeries iteration, you need to call the timesSeries done callback from the completion callback for the waterfall call. Right now, you are calling it long before that which means that timesSeries won't wait for the waterfall to be done.
You can do that by changing this:
], function(err, result) {
console.log('----- ' +page+ '-----');
});
next(null, 'done');
to this:
], function(err, result) {
console.log('----- ' +page+ '-----');
next(null, 'done');
});
It also seems odd that you have a hard-coded for loop limit of m < 150 rather than using the actual length of the content. You can easily run off the end of the content and potentially cause problems.
And, your error handling probably won't work well either. If you throw inside of the async request() callback, that's not going to go anywhere. You need much better error handling such as calling callback(error) to pass the error on to async.waterfall().
You also may want to surround all your DOM walking in a try/catch so if you throw any exceptions there, you can catch them yourself, analyze them and then fix the code.

if (tObj[m+1] && tObj[m+1].children != 0)

Can't get this keyword to work within a node module

I'm trying to build a small wrapper library for the node redis module.
var redis = require('redis'),
client = redis.createClient();
module.exports = {
/*
* Time To Live
*
* Time in seconds the cache will remain in
* memory.
*/
ttl: 120,
/*
* Time To Refresh
*
* Time buffer in seconds when the cache should
* be refreshed. On a cache check, if the ttl
* is less than the ttr, the cache will be
* refreshed.
*/
ttr: 60,
/*
* Check Cache
*
* Middleware to check if the request is cached
* before executing the full request.
*/
check: function (req, res, next) {
var key = req.url.slice(1, req.url.length).replace('/', ':');
client.get(key, function (err, value) {
if (value !== null) {
res.send(value);
client.ttl(key, function (err, ttl) {
if (ttl < this.ttr) {
return next();
}
return;
});
} else {
return next();
}
})
},
/*
* Set Cache
*
* Takes a key and a value and stores it in redis.
* Also takes the full response object "res" and
* handles sending the response if it has not
* already been sent.
*/
set: function (url, value, res) {
var key = url.slice(1, url.length).replace('/', ':');
client.set(key, value);
client.expire(key, this.ttl);
if (!res.headersSent) {
res.send(value);
}
return;
},
/*
* Keygen Cache
*
* Takes a urls substring and creates a keyname
* in line with redis best practices
*/
keygen: function (url) {
var key = url.slice(0,1).replace('/', ':');
console.log(key);
return key;
}
};
I can't figure out how to use the 'this' keyword properly. If I try to reference this.ttl or this.ttr or call this.keygen from another function within the module.exports object it always turns up undefined. What is a structure I should be using to enable referencing functions internal to the same object?

You have nested functions in your check function, so the this-keyword relates to the inner function context and not to your object.
First solution:
function (req, res, next) {
var _this = this;
var key = req.url.slice(1, req.url.length).replace('/', ':');
client.get(key, function (err, value) {
if (value !== null) {
res.send(value);
client.ttl(key, function (err, ttl) {
if (ttl < _this.ttr) {
return next();
}
return;
});
} else {
return next();
}
})
}
And if you are using the function as a callback function bind your object to the callback function like this:
// replace "yourModule" with the name of your module
var yourModule = require('./yourModule.js');
// an example for expressjs (use get, post ... or something else)
app.get('/some/url', yourModule.check.bind(yourModule));
Second solution (IMHO the better one):
Another solution is to use local variables in your module (these are only visible in your module -> and this is what you want).
This is way more easier:
/*
* Time To Live
*
* Time in seconds the cache will remain in
* memory.
*/
var ttl = 120;
/*
* Time To Refresh
*
* Time buffer in seconds when the cache should
* be refreshed. On a cache check, if the ttl
* is less than the ttr, the cache will be
* refreshed.
*/
var ttr = 60;
/*
* Check Cache
*
* Middleware to check if the request is cached
* before executing the full request.
*/
var check = function (req, res, next) {
var key = req.url.slice(1, req.url.length).replace('/', ':');
client.get(key, function (err, value) {
if (value !== null) {
res.send(value);
client.ttl(key, function (err, ttl) {
if (ttl < ttr) {
return next();
}
return;
});
} else {
return next();
}
})
};
/*
* Set Cache
*
* Takes a key and a value and stores it in redis.
* Also takes the full response object "res" and
* handles sending the response if it has not
* already been sent.
*/
var set = function (url, value, res) {
var key = url.slice(1, url.length).replace('/', ':');
client.set(key, value);
client.expire(key, ttl);
if (!res.headersSent) {
res.send(value);
}
return;
};
/*
* Keygen Cache
*
* Takes a urls substring and creates a keyname
* in line with redis best practices
*/
var keygen = function (url) {
var key = url.slice(0,1).replace('/', ':');
console.log(key);
return key;
};
/**
* PUBLIC API
*/
module.exports = {
check: check,
set: set,
keygen: keygen
};
Now because you are not relying on the context of the module you can simply do this:
// replace "yourModule" with the name of your module
var yourModule = require('./yourModule.js');
// an example for expressjs (use get, post ... or something else)
app.get('/some/url', yourModule.check);

Node/Express - How to wait until For Loop is over to respond with JSON

I have a function in my express app that makes multiple queries within a For Loop and I need to design a callback that responds with JSON when the loop is finished. But, I'm not sure how to do this in Node yet. Here is what I have so far, but it's not yet working...
exports.contacts_create = function(req, res) {
var contacts = req.body;
(function(res, contacts) {
for (var property in contacts) { // for each contact, save to db
if( !isNaN(property) ) {
contact = contacts[property];
var newContact = new Contact(contact);
newContact.user = req.user.id
newContact.save(function(err) {
if (err) { console.log(err) };
}); // .save
}; // if !isNAN
}; // for
self.response();
})(); // function
}; // contacts_create
exports.response = function(req, res, success) {
res.json('finished');
};

There are a few problems with your code besides just the callback structure.
var contacts = req.body;
(function(res, contacts) {
...
})(); // function
^ you are redefining contacts and res in the parameter list, but not passing in any arguments, so inside your function res and contacts will be undefined.
Also, not sure where your self variable is coming from, but maybe you defined that elsewhere.
As to the callback structure, you're looking for something like this (assuming contacts is an Array):
exports.contacts_create = function(req, res) {
var contacts = req.body;
var iterator = function (i) {
if (i >= contacts.length) {
res.json('finished'); // or call self.response() or whatever
return;
}
contact = contacts[i];
var newContact = new Contact(contact);
newContact.user = req.user.id
newContact.save(function(err) {
if (err)
console.log(err); //if this is really a failure, you should call response here and return
iterator(i + 1); //re-call this function with the next index
});
};
iterator(0); //start the async "for" loop
};
However, you may want to consider performing your database saves in parallel. Something like this:
var savesPending = contacts.length;
var saveCallback = function (i, err) {
if (err)
console.log('Saving contact ' + i + ' failed.');
if (--savesPending === 0)
res.json('finished');
};
for (var i in contacts) {
...
newContact.save(saveCallback.bind(null, i));
}
This way you don't have to wait for each save to complete before starting the next round-trip to the database.
If you're unfamiliar with why I used saveCallback.bind(null, i), it's basically so the callback can know which contact failed in the event of an error. See Function.prototype.bind if you need a reference.