My code is currently returning as 'undefined';
function findDoc(rowObj) {
Database.findOne(
{ 'name': rowObj.name },
'_id, foreign_id'
).exec((err, docs) => {
if (err) {
throw err;
} else {
return docs;
});
}
try {
console.log('before');
let searchDoc = await findDoc(rowObj);
console.log(searchDoc);
console.log('after');
} catch (err) {
console.log(err);
}
This outputs;
before
undefined
after
whereas if i change the findDoc function to console.log(docs); rather than return docs i get;
before
CORRECT OBJECT
after
How can i fix this to get the second result using the first structure where it returns to the main try catch block?
Thanks
You should either wrap your function with async or use a callback as follows :
function findDoc(rowObj,callback) {
Database.findOne(
{ 'name': rowObj.name },
'_id, foreign_id'
).exec((err, docs) => {
if (err) {
throw err;
} else {
callback(docs);
});
}
try {
console.log('before');
findDoc(rowObj,(searchDoc) => {
console.log(searchDoc);
console.log('after');
});
} catch (err) {
console.log(err);
}
Related
I am using node-async-loop for asyncronous programming
var array = ['item0', 'item1', 'item2'];
asyncLoop(array, function (item, next)
{
do.some.action(item, function (err)
{
if (err)
{
next(err);
return;
}
next();
});
}, function (err)
{
if (err)
{
console.error('Error: ' + err.message);
return;
}
console.log('Finished!');
});
Like this I am using three async loops one under one.
I want to send the response only after the third inner loop ends. How can I do so?.
Here is the link for node-async-loop (https://www.npmjs.com/package/node-async-loop)
here is my code which i writing but whnever i want to response when the last loop completes it say can set header after send to cliend.
also in console log i am getting data every time when data coming from query.
const id = req.params.id;
finalData = [];
tb_user.findOne({ where: { id: id } }).then((userRiverSys, err) => {
if (userRiverSys) {
// console.log(userRiverSys.regionJson)
asyncLoop(userRiverSys.regionJson, function (item, next) {
// console.log("item", item);
tb_riverSystems.findAll(
{
where: { regionId: item.id }
}).then((findriverSys, err) => {
if (err) {
next(err);
return;
}
// console.log("findriverSys", findriverSys);
if (findriverSys) {
asyncLoop(findriverSys, function (item1, next1) {
if (err) {
next(err);
return;
}
// console.log("item1", item1.dataValues);
tb_facilities.findAll(
{
where: { riverSystemId: item1.dataValues.id }
}).then((findFacilities) => {
if (findFacilities) {
// console.log("findFacilities", findFacilities[0].dataValues.name);
asyncLoop(findFacilities, function (item2, next2) {
if (err) {
next(err);
return;
}
tb_userAccess.findAll(
{
where: { facilityId: item2.dataValues.id }
}).then((userAccessFacilities, err) => {
// console.log("userAccessFacilities", userAccessFacilities[0].dataValues);
// var i = 0;
asyncLoop(userAccessFacilities, function (item3, next3) {
finalData.push({
UserId: item3.userid,
facilityId: item3.facilityId,
})
next3();
},
function (err) {
if (err) {
console.error('Error: ' + err.message);
return;
}
// i++;
// console.log('Finished!!!!');
// if (userAccessFacilities.length === i) {
// console.log("finalData", i);
// // res.json({"status":"true", "message":"update OrgChallenge"})
// }
})
return res.json({"status":"true", "message":"update OrgChallenge"})
// console.log("finalData", finalData);
})
next2();
}, function (err) {
if (err) {
console.error('Error: ' + err.message);
return;
}
console.log('Finished!!!');
});
}
});
next1();
}, function (err) {
if (err) {
console.error('Error: ' + err.message);
return;
}
console.log('Finished!!');
});
}
});
next();
}, function (err) {
if (err) {
console.error('Error: ' + err.message);
return;
}
console.log('Finished!');
});
} else {
console.log("err3", err)
}
})
If you promisify your asynchronous action (so it returns a promise), then you can just use a regular for loop and async/await and there is no need for a 3rd party library to sequence your asynchronous loop. This is modern Javascript:
const { promisify } = require('util');
do.some.actionP = promisify(do.some.action);
async function someFunction() {
const array = ['item0', 'item1', 'item2'];
for (let item of array) {
let result = await do.some.actionP(item);
// do something with result here
}
return someFinalResult;
}
someFunction().then(result => {
console.log(result);
}).catch(err => {
console.log(err);
});
FYI, in real code, many (or even most) asynchronous operations now offer promisified versions of their API already so usually you don't even need to do the promisify step any more. For example, pretty much all databases already offer a promise interface that you can just use directly.
const loop = async (arr, results = []) => {
const item = arr.shift()
if (!item) {
console.log("DONE");
return results;
}
// as async function
await new Promise(resolve => {
resolve(results.push(`asynced-${item}`))
})
return loop(arr, results);
}
(async () => {
const result = await loop(["item0", "item1", "item2"])
console.log(result);
})();
I'd be happy if I can help you.
but this script uses a recursive function instead of node-async-loop.
so this might not be suitable for you.
I am trying to develop an APP in which I have to increase or decrease the user count according to their hobbies/interest in the master list. I am doing it in Node js with the help of loopback. Here is my code, in which I am giving two interests(i.e sketching and horse-riding):
async.forEach(data, function (interest) {
console.log("Interest is", interest);
Interest.findOne({
where:
{
'name': interest
}
}, function (err, interestObj) {
if (err) {
//return callback(err, null);
console.log("error", err);
}
else {
//return callback(null, response);
console.log("found", interestObj);
if (!interestObj) {
Interest.create({ "name": interest, "count": 1 }, function (err, response) { });
}
else {
_count = interestObj.count + 1;
interestObj.updateAttribute('count', _count, function (e, r) { });
}
}
});
// return callback(null, {});
},function(err){
console.log("success..!!")
});
}
but it is showing me only one of them in output. Here is output:
data is [ 'horse-riding', 'skeching' ]
Interest is horse-riding
Interest is skeching
found { name: 'horse-riding', count: 1, id: 59ccff0765055a212491a6bc }
found null
I think the async function is not working properly with forEach loop in this, But I am not getting where the code went wrong. I want to show all the interest given by the user, so what course of actions should I take to do it?? Thanks in advance..!!:)
It is working now...!!!
async.each(data, function (interest, callback2) {
console.log('Processing ', interest);
Interest.findOne({
where:
{
'name': interest
}
}, function (err, interestObj) {
if (err) {
console.log("error", err);
callback2(err);
}
else {
console.log("found", interestObj);
if (!interestObj) {
Interest.create({ "name": interest, "count": 1 }, function (err, response) { });
}
else {
_count = interestObj.count + 1;
interestObj.updateAttribute('count', _count, function (e, r) { });
}
callback2();
}
});
}, function (err) {
if (err) {
console.log('Failed to process', err);
} else {
console.log('All interests have been processed successfully');
}
return callback(err);
})
};
Hi I have a problem running a loop and getting the return data using Promises.
I have a getStudentMarks method for getting students marks from the database in subject wise.
getStudentMarks: function(studentId, studentStandard) {
console.log("getStudentMarks invoked...");
return new Promise(function(resolve, reject) {
r.table('student_subjects').filter({
"studentId": studentId,
"studentStandard": studentStandard
}).pluck("subjectId", "subjectName").run(connection, function(err, cursor) {
if (err) {
throw err;
reject(err);
} else {
cursor.toArray(function(err, result) {
if (err) {
throw err
} else {
console.log(result.length);
if (result.length > 0) {
studentSubjectArray = result;
var studentMarksSubjectWiseArray = [];
studentSubjectArray.forEach(function(elementPhoto) {
r.table('student_marks').filter({
"studentId": studentId,
"subjectId": studentSubjectArray.subjectId
}).run(connection, function(err, cursor) {
if (err) {
throw err;
reject(err);
} else {
cursor.toArray(function(err, result_marks) {
var studnetMarksDataObject = {
subjectId: studentSubjectArray.subjectId,
subjectName: studentSubjectArray.subjectName,
marks: result.marks
};
studentMarksSubjectWiseArray.push(studnetMarksDataObject);
});
}
});
});
resolve(studentMarksSubjectWiseArray);
}
}
});
}
});
});
}
I'm invoking the method by,
app.post('/getStudentMarks', function(req, reqs) {
ubm.getStudentMarks(req.body.studentId, req.body.studentStandard)
.then((data) => {
console.log('return data: ' + data);
})
.catch((err) => {
console.log(err);
});
});
When I run the code its working absolutely fine there is no error. I get all the student marks object in the studentMarksSubjectWiseArray array. But the problem is even before the studentSubjectArray loops gets completed, the resolve is getting executed and I'm getting a blank array as return. How do I solve the problem. I understand that I'm not doing the Promises right. I'm new to Promises so I'm not being able to figure out the right way.
That happens because inside your studentSubjectArray.forEach statement you perform set of asynchronous operations r.table(...).filter(...).run() and you push their result into the array. However, those actions finish after you perform the resolve(), so the studentMarksSubjectWiseArray is still empty. In this case you would have to use Promise.all() method.
let promisesArray = [];
studentSubjectArray.forEach((elementPhoto) => {
let singlePromise = new Promise((resolve, reject) => {
// here perform asynchronous operation and do the resolve with single result like r.table(...).filter(...).run()
// in the end you would perform resolve(studentMarksDataObject)
r.table('student_marks').filter({
"studentId": studentId,
"subjectId": studentSubjectArray.subjectId
}).run(connection, function(err, cursor) {
if (err) {
throw err;
reject(err);
} else {
cursor.toArray(function(err, result_marks) {
var studnetMarksDataObject = {
subjectId: studentSubjectArray.subjectId,
subjectName: studentSubjectArray.subjectName,
marks: result.marks
};
resolve(studnetMarksDataObject);
});
}
});
});
promisesArray.push(singlePromise)
});
Promise.all(promisesArray).then((result) => {
// here the result would be an array of results from previously performed set of asynchronous operations
});
I'm trying to adopt bluebird Promise for my existing project which uses sails.js, here's the snippet:
var isUserTeamCaptain = function(userId, teamId) {
return new Promise(function(resolve, reject) {
Team.findOne({id: teamId}).then(function(team) {
if (team) {
if (userId != team.captain) {
reject(sails.__('you are not captain, thus cannot edit team info'));
} else {
resolve(team);
}
} else {
reject(sails.__('team not found'));
}
}).catch(function(err) {
reject(err);
});
});
};
isUserTeamCaptain('5604145aa8944407362d6abf', '560496d157f6995702b3f931').then(
function resolve(team) {
console.log('passed');
return Promise.resolve(User.find());
},
function reject(err) {
console.log('failed');
console.log('the error: ' + err);
throw new Error(err);
}
).each(function(user) {
console.log(user.username);
}).then(function() {
console.log('we are done with each iteration')
}).catch(function(err) {
console.log(err.message);
})
It works great, each username can be printed in console, so can 'we are done with each iteration', also in the order I expected.
BUT, if I put the isUserTeamCaptain in another js file, say 'TeamService.js', export and inject TeamService here and then refactor the above snippet of code like so:
TeamService.isUserTeamCaptain('5604145aa8944407362d6abf', '560496d157f6995702b3f931').then(
function resolve(team) {
console.log('passed');
return Promise.resolve(User.find());
},
function reject(err) {
console.log('failed');
console.log('the error: ' + err);
throw new Error(err);
}
).each(function(user) {
console.log(user.username);
}).then(function() {
console.log('we are done with each iteration')
}).catch(function(err) {
console.log(err.message);
})
It complains about
.each(function(user) { ...
being an UNDEFINED FUNCTION. Did I miss anything here?
UPDATE: this is the TeamService.js:
// TeamService.js - in api/services
var TeamService = module.exports = {
/**
* Promise version of isUserCaptainOfTeam
*/
isUserTeamCaptain: function(userId, teamId) {
return new Promise(function(resolve, reject) {
Team.findOne({id: teamId}).then(function(team) {
if (team) {
if (userId != team.captain) {
reject(sails.__('you are not captain, thus cannot edit team info'));
} else {
resolve(team);
}
} else {
reject(sails.__('team not found'));
}
}).catch(function(err) {
reject(err);
});
});
}
};
UPDATE: kinda found out where my problem was, I missed
var Promise = require('bluebird');
in TeamService.js...
I have this async.parallel functionality inside an aysnc.eachSeries call.
I hardcoded an error so I could pass it, to see if it was behaving the way I thought. For some reason, when I pass an error, it doesn't get thrown in the final callback named "doneWithSeries".
async.eachSeries(jsonDataArr, function iterator(item, callback) {
async.parallel([
function (cb) {
if (item.hasOwnProperty('event.type')) {
var event_type = item['event.type'];
delete item['event.type'];
try {
var json = JSON.stringify(item);
}
catch (err) {
throw err;
}
fs.writeFile('./enriched_data/' + event_type + '.json', json, function (err) {
if (err) {
cb(err);
}
else {
cb(null);
}
});
}
},
function (cb) {
if (item.hasOwnProperty('status_desc')) {
var status_desc = item['status_desc'];
delete item['status_desc'];
try {
var json = JSON.stringify(item);
}
catch (err) {
throw err;
}
fs.writeFile('./enriched_data/' + status_desc + '.json', json, function (err) {
if (err) {
cb(err);
}
else {
cb(null);
}
});
}
}
],
function doneWithParallel(err) {
callback(new Error('throw this baby')); //shouldn't the first incident of error pass the error straight to the doneWithSeries callback below?
})
},
function doneWithSeries(err) {
if (err) {
throw err;
}
else {
console.log('success');
}
});
here is a distilled version of the code without anything unnecessary:
var async = require('async');
async.eachSeries(['1', '2'], function (item, callback) {
async.parallel([
function (cb) {
setTimeout(function () {
cb(null, 'one');
}, 200);
},
function (cb) {
setTimeout(function () {
cb(null, 'two');
}, 100);
}
],
function doneWithParallel(err, results) {
console.log('results', results);
callback(new Error('duh'));
})
},
function doneWithSeries(err) {
if (err)
throw err;
});
indeed that works. can't figure out why my code above doesn't, accept perhaps that the array could be empty even though when I run my code the success message gets logged...weird.
I think that's expected behavior if your list is empty. async will always call the final callback with no error even if there is no input list.