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Async/Await : called function is not awiting and returning value

Hello I am creating 1 function with dynamic arguments where as I am calling api and on defined route I am calling express middleware function and from there I am calling another dynamic function which will help me to insert data into the database.
I am using Sequalize ORM
Here is code:
var async = require('async');
// Models
var LogSchema = require('../models/Logs')
module.exports = {
insertLog: async (req, res) => {
let result = await insertLogFn('1', 'method_name()', 'module_name_here', 'req.body', '{ api response }', 'action', '24')
console.log("result", result)
res.status(200).json(result)
}
};
function insertLogFn(status, invokedMethodName, moduleName, bodyRequest, apiResponse = null, actionName = null, userId) {
async.waterfall([
(nextCall) => {
let dataToBeInserted = {}
dataToBeInserted.status = status,
dataToBeInserted.invoked_method_name = invokedMethodName,
dataToBeInserted.module_name = moduleName,
dataToBeInserted.body_request = bodyRequest,
dataToBeInserted.api_response = apiResponse
dataToBeInserted.action_name = actionName,
dataToBeInserted.user_id = userId
LogSchema.create(dataToBeInserted).then(res => {
const dataObj = res.get({plain:true})
nextCall(null, {
status: 200,
message: "Log inserted successfully",
data: dataObj
})
}).catch(err => {
})
}
], (err, response) => {
if(err) {
}
return response
})
}
In module.export I have added insertLog function which is getting called in api and from there I am calling insertLogFn() which is declared outside of the module.export.
I am able to get inserted result in function insertLogFn() but the things is await is not working and not waiting for the result.
What I want to do is to wait till insertLogFn gets executed and the returned response has to be stored in the variable and return it as an api response.

You cannot. As per my understanding, IMO, Thumb rule is "Async/Await operation should return a promise"
function insertLogFn(status, invokedMethodName, moduleName, bodyRequest, apiResponse = null, actionName = null, userId) {
async.waterfall([
(nextCall) => {
let dataToBeInserted = {}
dataToBeInserted.status = status,
dataToBeInserted.invoked_method_name = invokedMethodName,
dataToBeInserted.module_name = moduleName,
dataToBeInserted.body_request = bodyRequest,
dataToBeInserted.api_response = apiResponse
dataToBeInserted.action_name = actionName,
dataToBeInserted.user_id = userId
LogSchema.create(dataToBeInserted).then(res => {
const dataObj = res.get({plain:true})
nextCall(null, {
status: 200,
message: "Log inserted successfully",
data: dataObj
})
return ;
console.log("you should return something here<-------");
}).catch(err => {
})
}
], (err, response) => {
if(err) {
}
return response
})
}
Now the answer will be clear if you read this one from Bergi: https://stackoverflow.com/a/40499150/9122159

How can I convert the following JavaScript Promise into regular asychronous code?

Hi I'm working with the following code snippet:
imaps.connect(config).then(function (connection) {
connection.openBox('INBOX').then(function () {
// Fetch emails from the last 24h
var delay = 24 * 3600 * 1000;
var yesterday = new Date();
yesterday.setTime(Date.now() - delay);
yesterday = yesterday.toISOString();
var searchCriteria = ['UNSEEN', ['SINCE', yesterday]];
var fetchOptions = { bodies: ['HEADER.FIELDS (FROM TO SUBJECT DATE)'], struct: true };
// retrieve only the headers of the messages
return connection.search(searchCriteria, fetchOptions);
}).then(function (messages) {
var attachments = [];
messages.forEach(function (message) {
var parts = imaps.getParts(message.attributes.struct);
attachments = attachments.concat(parts.filter(function (part) {
return part.disposition && part.disposition.type.toUpperCase() === 'ATTACHMENT';
}).map(function (part) {
// retrieve the attachments only of the messages with attachments
return connection.getPartData(message, part)
.then(function (partData) {
return {
filename: part.disposition.params.filename,
data: partData
};
});
}));
});
return Promise.all(attachments);
}).then(function (attachments) {
console.log(attachments);
// =>
// [ { filename: 'cats.jpg', data: Buffer() },
// { filename: 'pay-stub.pdf', data: Buffer() } ]
});
I'm trying to remove Promises and turn the code into code using callbacks.
At the moment, I'm looping through all the attachments and when I print an individual attachment to the console I get:
Promise { <pending> }
How can I convert the code to regular callback code such that I can access the 'filename' and 'data' attributes of the attachment?

Actually, I don't understand why you need to go back from a promise to a callback but you can use the following code. It just a promise converter:
const promiseToCallback = function (promise) {
if (!isFn(promise.then)) {
throw new TypeError('Expected a promise');
}
return function (cb) {
promise.then(function (data) {
setImmediate(cb, null, data);
}, function (err) {
setImmediate(cb, err);
});
};
};
To use it
promiseToCallback(promise)(function(err, data) {
...
});

How to avoid a callback in promise

I am new to NodeJS and JavaScript. I am badly stuck in a problem:
I want to generate QR image of 'some text' and after generating it, I want to query my MySQL database and insert the image to database.
Problem is that QRCode.toDataURL of SOLDAIR module goes in running state and query is called before the QR image is returned from the .toDataUrl function.
Hence it results in error.
I tried everything, promises, nested promises, counters, if statements etc., but I am unable to find a solution.
My code:
router.post('/generateTicket', (req,res) => {
const query1 = `SELECT * FROM booking ORDER BY bookingID DESC LIMIT 1`;
const query2 = `INSERT INTO ticket (ticket_image,BookingID) SET ?`;
let bookingID;
let count;
let ticket_data = {};
Promise.using(mysql.getSqlConn(), conn => {
conn.query(query1).then(resultOfQuery1 => {
bookingID = resultOfQuery1[0].BookingID;
count = resultOfQuery1[0].PeopleCount;
console.log("ID = " + bookingID + " people count = "+count);
promiseToCreateQRcode().then(function (URLfromResolve) {
console.log("the url is " + URLfromResolve );
}).catch(function (fromReject) {
console.log("Rejected "+ fromReject);
}); // catch of promise to create QR
}).catch(err => {
res.json({ status: 500, message: 'Error Occured in query 1 ' + err });
}); // catch of query 1
});
});
var opts = {
errorCorrectionLevel: 'H',
type: 'image/png',
rendererOpts: {
quality: 0.3
}
};
let promiseToCreateQRcode = function () {
let QRImage;
return new Promise(function (resolve,reject) {
QRCode.toDataURL('text', function (err, url) {
if (err) throw err
console.log("\n"+url+"\n");
QRImage = url;
});
if (QRImage)
resolve(QRImage);
else
reject("error occured in url");
});
};
As u can see, the program jumps to if statement and the QR image is not generated yet, hence it goes in "reject":

Try this,
let promiseToCreateQRcode = function () {
return new Promise(function (resolve,reject) {
QRCode.toDataURL('text', function (err, url) {
if (err){
reject(err); // or some message
} else {
resolve(url);
}
});
});
};
This way promise will be resolved only when toDataURL returns QR image.

Have a look at How do I convert an existing callback API to promises?. You need to call resolve or reject in the asynchronous callback!
function promiseToCreateQRcode() {
return new Promise(function(resolve,reject) {
QRCode.toDataURL('text', function (err, url) {
if (err) {
reject(err);
} else {
console.log("\n"+url+"\n");
resolve(url);
}
});
});
}
Using this extra QRImage variable like you did cannot work.

function not returning with promise

I'm trying to call a function (refresh_access_token) from another one and create a Promise chain from that. But the return function inside refresh_access_token is not working. The refresh_access_token doesn't return to it's caller when it completes.
I'm receiving this message:
Unhandled rejection TypeError: Cannot read property 'then' of undefined
How can I fix this?
These are the 2 function code:
exports.refresh_access_token = function(environment_hash) {
var MercadoLibre = require('../../models/index').MercadoLibre;
var needle = require('needle');
const load = require('express-load');
var meli = require('mercadolibre');
var request=require('request');
const mysql = require('mysql');
const dotenv = require('dotenv').config({path: '../../.env'});
var oauth_url = 'https://api.mercadolibre.com/oauth/token';
var env_hash = environment_hash;
where = { environment_hash: env_hash };
MercadoLibre.findOne({where: where}).then(function (account) {
if (!account) {
// Item not found
} else {
// Found an item, update it
needle.post(oauth_url, {
grant_type: 'refresh_token',
client_id: process.env.MERCADOLIBRE_CLIENT_ID,
client_secret: process.env.MERCADOLIBRE_SECRET,
refresh_token: account.refresh_token
}, {
}, function (err, res, body) {
if (body) {
expires_in = new Date();
expires_in.setUTCHours(0);
expires_in.setTime(expires_in.getTime() + 21600*1000);
values = {
refresh_token: body.refresh_token,
expires_in: expires_in
};
where = { environment_hash: env_hash };
return MercadoLibre.update(values, {where: where});
}
});
}
});
}
exports.run_mercadolibre_jobs = function() {
var MercadoLibre = require('../../models/index').MercadoLibre;
var values = {
attributes: ['environment_hash'],
raw: true
};
MercadoLibre
.findAll(values)
.then(function(accounts) {
Promise.all(accounts.map(function(account) {
module.exports.refresh_access_token(account.environment_hash)
.then(function(response) {
console.log(response);
})
.catch(function(response){
console.log(response);
});
}));
});
}

Your function refresh_access_token is not returning anything. Your only return statement is inside the needle.post callback. You should be first returning:
return MercadoLibre.findOne(...);
However, you are mixing promises, with callbacks (used in your needle.port call). I would suggest reviewing Promises vs Callbacks and how to use them together. Here is a good thread on how to convert callback-apis to promises: How do I convert an existing callback API to promises?.
Another alternative would be to replace using needle with a promise-supported node library:
Axios
Request Promise

Node.js: What techniques are there for writing clean, simple callback code?

node.js code is known for turning into callback spaghetti.
What are the best techniques for overcoming this problem and writing clean, uncomplex, easy to understand callback code in node.js?

Take a look at Promises: http://promises-aplus.github.io/promises-spec/
It is an open standard which intended to solve this issue.
I am using node module 'q', which implements this standard: https://github.com/kriskowal/q
Simple use case:
var Q = require('q');
For example we have method like:
var foo = function(id) {
var qdef = Q.defer();
Model.find(id).success(function(result) {
qdef.resolve(result);
});
return (qdef.promise);
}
Then we can chain promises by method .then():
foo(<any-id>)
.then(function(result) {
// another promise
})
.then(function() {
// so on
});
It is also possible to creating promise from values like:
Q([]).then(function(val) { val.push('foo') });
And much more, see docs.
See also:
http://jeditoolkit.com/2012/04/26/code-logic-not-mechanics.html#post
http://wiki.commonjs.org/wiki/Promises/A

Several things can be done to avoid the 'matrioska-style'.
You can store callbacks to variables:
var on_read = function (foo, bar) {
// some logic
},
on_insert = function (err, data) {
someAsyncRead(data, on_read);
};
someAsyncInsert('foo', on_insert);
You can use some modules that help in those scenarios.
// Example using funk
var funk = require('funk');
for(var i = 0; i < 10; i++) {
asyncFunction(i, funk.add(function (data) {
this[i] = data;
}));
}
funk.parallel(function () {
console.log(this);
});

I'd suggest 1) using CoffeeScript and 2) using named callbacks and passing state between them in a hash, rather than either nesting callbacks or allowing argument lists to get very long. So instead of
var callback1 = function(foo) {
var callback2 = function(bar) {
var callback3 = function(baz) {
doLastThing(foo, bar, baz);
}
doSomethingElse(bar, callback3);
}
doSomething(foo, callback2);
}
someAsync(callback1);
you can instead simply write
callback1 = (state) -> doSomething state.foo, callback2
callback2 = (state) -> doSomethingElse state.bar, callback3
callback3 = (state) -> doLastThing state
someAsync callback1
once your doSomething, doSomethingElse and doLastThing have been rewritten to use/extend a hash. (You may need to write extra wrappers around external functions.)
As you can see, the code in this approach reads neatly and linearly. And because all callbacks are exposed, unit testing becomes much easier.

Try node-line
https://github.com/kevin0571/node-line
Usage:
var line = require("line");
line(function(next) {
obj.action1(param1, function(err, rs) {
next({
err: err,
rs: rs
});
});
}, function(next, data) {
if (data.err) {
console.error(err);
return;
}
obj.action2(param2, function(err, rs) {
if (err) {
console.error(err);
return;
}
next(rs);
});
}, function(rs) {
obj.finish(rs);
});

For the most part, working Twitter OAuth2 application-only example, using Kris' Q promise library with https.request, Nodejs Express api route. First attempt user timeline GET. If 401 response, refreshing bearer-token then retry user timeline. I had to use Q.when to handle a promise that returns another promise (chaining) or a value.
/**
* Using Rails-like standard naming convention for endpoints.
* GET /things -> index
* POST /things -> create
* GET /things/:id -> show
* PUT /things/:id -> update
* DELETE /things/:id -> destroy
*/
'use strict';
// var _ = require('lodash');
var http = require('http');
var https = require('https');
var querystring = require('querystring');
var Q = require('q')
// Get list of twtimelines
exports.index = function(req, res) {
var tid = req.query.tid
if (tid) {
Q.when(reqTimeline(tid, true, res), function(value) {
// > value
// 404
// > body1
// '{"errors":[{"code":34,"message":"Sorry, that page does not exist."}]}'
})
} else {
res.json({
errors: [{
message: 'no tid specified in query'
}]
});
}
};
function reqPromise(options, postData) {
var deferred = Q.defer()
var req = https.request(options, function(res) {
// console.log("statusCode: ", res.statusCode);
// console.log("headers: ", res.headers);
var statusCode = res.statusCode
deferred.notify(res)
res.on('data', function(d) {
//process.stdout.write(d);
deferred.notify(d)
}).on('end', function() {
deferred.resolve(statusCode)
});
});
req.on('error', function(e) {
console.error(e);
deferred.reject(e)
});
req.write(postData);
req.end();
return deferred.promise
} // deferRequest
function isIncomingMessage(ot) {
return ot instanceof http.IncomingMessage
}
function isBuffer(ot) {
return ot instanceof Buffer
}
function reqTimeline(screen_name, reqBearerTokenOn401, res) {
var optionsUserTimeline = {
hostname: 'api.twitter.com',
path: '/1.1/statuses/user_timeline.json?' + querystring.stringify({
count: '3',
screen_name: screen_name
}),
method: 'GET',
headers: {
//'Authorization': 'Bearer ' + JSON.parse(body1).access_token
'Authorization': 'Bearer ' + process.env.BEARER_TOKEN
} // headers
};
console.log("optionsUserTimeline", optionsUserTimeline)
var statusCode;
var body1 = new Buffer(''); // default utf8 string buffer ?
return reqPromise(optionsUserTimeline, '')
.then(function(value) { // done
if (reqBearerTokenOn401 && value === 401) {
console.log("reqTimeline - requesting bearer token")
return reqBearerToken(screen_name, res)
}
console.log("reqTimeline - done done:", value)
res.end()
return value
},
function(reason) { // error
console.log("reqTimeline - error:", body1)
},
function(progress) {
console.log("reqTimeline - progress:", body1)
if (isIncomingMessage(progress)) {
body1 = body1.slice(0, 0) // re-set buffer
statusCode = progress.statusCode;
if (reqBearerTokenOn401 && statusCode === 401) {
// readyn for retry
} else {
res.writeHead(statusCode)
}
} else if (isBuffer(progress)) {
if (reqBearerTokenOn401 && statusCode === 401) {
body1 += progress
} else {
res.write(progress)
}
} else {
throw "reqTimeline - unexpected progress"
}
});
} // reqTimeline
function reqBearerToken(screen_name, res) {
var postData = querystring.stringify({
'grant_type': 'client_credentials'
})
var optionsBearerToken = {
hostname: 'api.twitter.com',
path: '/oauth2/token',
method: 'POST',
headers: {
'Authorization': 'Basic ' + new Buffer(
process.env.CONSUMER_KEY + ":" + process.env.CONSUMER_SECRET
).toString('base64'),
'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8',
'Content-Length': postData.length
} // headers
}
// console.log("key", process.env.CONSUMER_KEY)
// console.log("secret", process.env.CONSUMER_SECRET)
// console.log("buf", new Buffer(
// process.env.CONSUMER_KEY + ":" + process.env.CONSUMER_SECRET
// ).toString())
console.log("optionsBearerToken", optionsBearerToken)
var body2 = new Buffer(''); // default utf8 string buffer ?
return reqPromise(optionsBearerToken, postData)
.then(function(value) { // done
console.log("reqBearerToken - done:", body2)
if (value === 200) {
console.log("reqBearerToken - done done")
process.env.BEARER_TOKEN = JSON.parse(body2).access_token;
return reqTimeline(screen_name, false, res)
}
return value
}, function(reason) {
throw "reqBearerToken - " + reason
}, function(progress) {
if (isIncomingMessage(progress)) {
body2 = body2.slice(0, 0) // reset buffer
} else if (isBuffer) {
body2 += progress
} else {
throw "reqBearerToken - unexpected progress"
}
});
} // reqBearerToken