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How to access await function variable outside function in Node.js

I am trying to implement an await function which local variable I am trying to access outside the function. However, I'm not getting the value which is defined inside function.
async CreateProduceRateAsset(data, callback) {
// Create a new file system based wallet for managing identities.
try {
var TimeStamp = new Date();
var TxId = '';
var blockNumber = '';
const result = await contract.submitTransaction('CreateProduceRateAsset', args);
await network.addBlockListener('block-listener', (err, block) => {
if (err) {
console.log(err);
return;
}
TimeStamp = block.data.data[0].payload.header.channel_header.timestamp;
var Tx_id = block.data.data[0].payload.header.channel_header.tx_id;
var BlockNO = block.header.number;
console.log('TxId', Tx_id)
console.log('blockNumber', BlockNO)
TxId = Tx_id
blockNumber = BlockNO
return TimeStamp, Tx_id, BlockNO
});
console.log('Timestamp', TimeStamp)
console.log('TxId 123', TxId)
console.log('blockNumber 123', blockNumber)
response.data = result
return callback(response);
} catch (error) {
response.httpstatus = 404;
response.message = `Failed to get MVP Price ${error.message} `;
return callback(response);
}
};
In the above code, I want to access Tx_id, Timestamp and BlockNO. For that, I am assigning a local variable to a global variable, however, I'm still getting the value of those as blank.
Could someone help me to get those values?

if I understand network.addBlockListener is a callback-based API and not return a promise so you cant await it, I guessed that you use https://hyperledger.github.io/fabric-sdk-node/release-1.4/module-fabric-network.Network.html
Here is your code with my comments
async CreateProduceRateAsset(data, callback) {
// Create a new file system based wallet for managing identities.
try {
var TimeStamp = new Date();
var TxId = '';
var blockNumber = '';
const result = await contract.submitTransaction('CreateProduceRateAsset', args);
// --> this api is callback based and wont not return a promise so you cant await it
await network.addBlockListener('block-listener', (err, block) => {
if (err) {
console.log(err);
return;
}
TimeStamp = block.data.data[0].payload.header.channel_header.timestamp;
// --> becasue you are inside a function these vars are not the same as the one ouside the call back , becasue they are scoped to this function
var Tx_id = block.data.data[0].payload.header.channel_header.tx_id;
var BlockNO = block.header.number;
console.log('###########TxId#####################', Tx_id)
console.log('###########blockNumber#####################', BlockNO)
TxId = Tx_id
blockNumber = BlockNO
// --> you can only return one value in js, also this reurn is useless since you dont call this callback
// --> better way to get these vars outside the callback is to pass them to your own callbak like this `callback(response,TimeStamp, Tx_id, BlockNO)`
return TimeStamp, Tx_id, BlockNO
});
console.log('*************** Timestamp:: **********************', TimeStamp)
console.log('###########TxId#####################123', TxId)
console.log('###########blockNumber#####################123', blockNumber)
response.data = result
return callback(response);
} catch (error) {
// if(error) throw error;
// response.error = error;
response.httpstatus = 404;
response.message = `Failed to get MVP Price ${error.message} `;
return callback(response);
}
};
if you need to use async/await with network.addBlockListener you can use utils.promisify to convert it to promise-based API but I don't recommend it since this an event listener

You have to put your return into a variable like this:
var data = await network.addBlockListener('block-listener', (err, block) => {
if (err) {
console.log(err);
return;
}
TimeStamp = block.data.data[0].payload.header.channel_header.timestamp;
var Tx_id = block.data.data[0].payload.header.channel_header.tx_id;
var BlockNO = block.header.number;
console.log('###########TxId#####################', Tx_id)
console.log('###########blockNumber#####################', BlockNO)
TxId = Tx_id
blockNumber = BlockNO
return {TimeStamp, Tx_id, BlockNO};
});
console.log('*************** Timestamp:: **********************', data.TimeStamp)
console.log('###########TxId#####################123', data.Tx_id)
console.log('###########blockNumber#####################123', data.BlockNO)
Now you can store all your values into data and put them into the desired variables.

angularJS / handing over parameter

In my AngularJS controller, I have the following code:
$scope.readMDB = function () {
var fs = require('fs');
var adodb = require('node-adodb');
var password = document.forms["mdbSelForm"]["pwd"].value;
var revSQL = fs.readFileSync('revenue.sql', 'utf-8');
revSQL = revSQL.replace(/(\r\n|\n|\r)/gm, " ");
revSQL = revSQL.replace(/[ä]/g, function () { return unescape("%E4") });
$scope.revenueSQL = String(revSQL);
console.log("revSQL: " + $scope.revenueSQL);
connection = adodb.open('Provider=Microsoft.Jet.OLEDB.4.0;Data Source=' + $scope.selectedMDB + ';Jet OLEDB:Database Password=' + password + ';');
// debug
adodb.debug = true;
connection
.query($scope.revenueSQL)
.on('done', function (data) {
var revAll = JSON.stringify(data);
var revenueData = JSON.parse(revAll).records;
fs.writeFile('./model/revenue.json', JSON.stringify(data), function (err) {
if (err) throw err;
console.log("revenue.json saved");
});
return true;
})
.on('fail', function (data) {
return false;
});
}
A similar code worked fine while not using Angular. Now, it doesn't work no more, because of the
connection.query($scope.revenueSQL)
part. More precisely, the $scope.revenueSQL is not recognized as the SQL Statement that it actually is. Putting the SQL directly, without reading it from a file, works fine. Still, looking at my console, I see that $scope.revenueSQL is exactly what I want. But being put as parameter into .query(), something seems to go wrong. Any ideas?

Try
$scope.revenueSQL = $scope.$eval(String(revSQL));
to execute the expression on the current scope and returns the result.

Async Recursion with JavaScript and Node.js

This is probably a noob JavaScript question, but I'm looking to know if my solution to a problem I am having is 'correct'
I have created the following sample application that recreates my error:
Firstly in index.js
var processor = require('./fileProcessor/processor.js');
var container = {
source: "source.txt",
destination: "destination.txt"
};
new processor().process(container);
I create my container object which has the name of the source file and the name of the destination file. This is passed into the process function of the processor:
var fileProcessor = require('./fileProcessor.js');
module.exports = function Processor() {
this.process = function(container) {
var file = new fileProcessor();
if(container.finished === undefined) {
if(container.body === undefined) {
file.read(container, this.process);
} else {
file.write(container, this.process);
}
}
};
};
As you can see this calls the read and write functions passing in the container and the process function as the callback, the fileProcessor looks like this:
var fs = require('fs');
module.exports = function() {
this.read = function(container, callback) {
fs.readFile(container.source, function (err, data) {
if(err) throw err;
container.body = data;
callback(container);
});
};
this.write = function(container, callback) {
fs.writeFile(container.destination, container.body, function(err) {
if(err) {
return console.log(err);
}
container.finished = true;
callback(container);
});
};
};
In simple terms the processor calls file.read, which reads the file and calls back into the process function, which then calls the write function. However at the end of the write function an error is thrown:
callback(container);
^
TypeError: object is not a function
Obviously when passing in this.process to file.write(container, this.process); the this isn't the this I intend it to be!
If I update my processor by adding a processFunction variable:
var fileProcessor = require('./fileProcessor.js');
module.exports = function Processor() {
var processFunction = function(container) {
var file = new fileProcessor();
if(container.finished === undefined) {
if(container.body === undefined) {
file.read(container, processFunction);
} else {
file.write(container, processFunction);
}
}
};
this.process = function(container) {
processFunction(container);
};
};
Everything works fine. Is this a good way to do this or is there a better solution?

I think this is a fine way to do it. There is one possible modification that you might make. Since you are creating a new name in your scope just for the purpose of recursing, you could just name your function and refer to it by its name inside of the function.
module.exports = function Processor() {
this.process = function processFunction(container) {
var file = new fileProcessor();
if(container.finished === undefined) {
if(container.body === undefined) {
file.read(container, processFunction);
} else {
file.write(container, processFunction);
}
}
};
};
Then you can avoid creating a name (processFunction) that will be visible outside the function.
Take a look here for reference:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/function#Named_function_expression

Send a return through a mongoose model

So I have this model :
'use strict';
var mongoose = require('mongoose');
var subscriberModel = function () {
var subscriberSchema = mongoose.Schema({
email: String
});
function validateEmail(email) {
var re = /^(([^<>()[\]\\.,;:\s#\"]+(\.[^<>()[\]\\.,;:\s#\"]+)*)|(\".+\"))#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
return re.test(email);
}
subscriberSchema.methods.validateSubscriber = function (subs, otherModel) {
var code = 0;
if (validateEmail(subs.email)) {
mongoose.model('Subscriber').findOne({'email': subs.email},
function(err, subscriber){
if (err) {
code = 2;
} else if (subscriber) {
code = 3;
} else {
subs.save(function(err){
if (err) {
code = 2;
}
code = 4;
});
}
});
} else {
code = 1;
}
};
return mongoose.model('Subscriber', subscriberSchema);
};
module.exports = new subscriberModel();
And I call it in another file that way :
var subscriberModel = require('../models/subscriber');
var subscriber = new subscriberModel({email: req.body.email.trim()});
var code = subscriber.validateSubscriber(subscriber, buyModel);
console.log('code = %s', code); // => displays "code = 0"
I guess it's a scope problem or something like that (because I don't use any callback -or maybe I should-) but I can't find nor the problem, nor the solution.
So, how can I get the returned code value ?
Thanks in advance.
[EDIT] : I found where the problem was and edited the code to explain it. So apparently my var is set in the callbacks of mongoose so now my question is; how do I wait for this callback to end as I need the result to display a message to the user in a webpage?

Okay so, I found the answer.
I edited my function validateSubscriber to send a callback: subscriberSchema.methods.validateSubscriber = function (subs, callback). And removed the otherModel occurences inside.
That way, when I call it in my other file I just have to do :
subscriber.validateSubscriber(subscriber, function(code){
buyModel.code = code;
console.log('code = %s', buyModel.code);
}
To get the code AND wait for the answer.
I hope it helped someone else.

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.