I have a function which uses async.parallel function to call two functions. But I don't know how to handle errors when async.parallel is used. If one of the two functions throw errors, how do I handle them?
exports.getProductconfigWithProductList = function(req, res){
var apiVersion = req.param('version', null);
var product_id = req.params.productId;
dbDriver = determineDriver('es');
async.parallel([
function(callback) {
dbDriver.getProductconfig(product_id,function(data){
callback(null, data);
});
},
function(callback) {
var productListPromise = getProductListData();
productListPromise.then(function(data) {
callback(null, data);
});
}
],
function(err, results) {
if(!err){
var data = results[0];
data[1] = results[1];
res.send(data);
res.end();
} else {
console.log('<<<<<<<<<<<<<<'+err+'>>>>>>>>>>>>>>>');
res.send(err);
res.end();
}
}
);
};
When you have:
async.parallel([
func1,
func2,
], (err, data) => {
if (err) {
// you handle the errors here
}
});
It's explained in more detail in the docs:
https://caolan.github.io/async/docs.html
and in the issue on GitHub here:
https://github.com/caolan/async/issues/334
Related
The callback function is not working as expected in a waterfall on async.for each limit.
When I remove that rest api call and if I call callback(null,arg2) it is working as expected, I think the problem with callback function or some api call in the below code.
var async = require("async");
var users = [1, 2, 3, 45]; // Initialize user array or get it from DB
var e = [];
var unirest = require("unirest");
var data = function() {
return new Promise((resolve, reject) => {
async.forEachLimit(
users,
1,
function(user, userCallback) {
async.waterfall(
[
function(callback) {
console.log(user);
callback(null, user);
},
function(arg1, callback) {
console.log(arg1);
callback(null, arg1);
},
function(arg2, callback) {
unirest
.get("http://dummy.restapiexample.com/api/v1/employee/1")
.end(function(response) {
if (response.error) callback("null", "data");
else callback(null, arg2);
});
}
],
function(err, result) {
if (err) {
console.log("err");
reject(e);
} else {
console.log("done", result);
e.push(result);
userCallback();
resolve(e);
}
}
);
},
function(err, result) {
console.log("User For Loop Completed", err, result);
}
);
});
};
I'm getting output as
expected outputs as
It turns a funny error in Node.js mongodb, if I put the form below:
locals.collection.find(filter, req.query);
returns me the following error:
MongoError: query selector must be an object
Now if I manually put the query works.
I'm having this problem a long time, and I've tried several ways.
locals.collection.find({slug:'somak'}, req.query);
I am using the following function:
exports.findAll = function(req, res, next) {
var locals = {},
section = req.params.section,
query = req.query,
filter = {};
if(query.filter) {
filter = query.filter.replace(/"(\w+)"\s*:/g, '$1:');
filter = filter.replace(/["]/g, "'");
}
console.log(filter);
delete query.filter;
async.series([
function(callback) {
MongoClient.connect(url, function(err, db) {
if (err) return callback(err);
locals.collection = db.collection(section);
callback();
});
},
function(callback) {
locals.collection.count(filter, function (err, result){
if (err) return callback(err);
locals.count = result;
callback();
});
},
function(callback) {
var cursor = locals.collection.find({slug:'somak'}, req.query);
if(req.query.page) {
cursor = cursor.skip(Math.abs(req.query.limit) * --req.query.page);
}
cursor.toArray(function(err, docs) {
if (err) return callback(err);
locals.docs = docs;
callback();
});
}
],
function(err) { //This function gets called after the three tasks have called their "task callbacks"
if (err) return next(err);
// Here locals will be populated with 'count' and 'docs'
res.json({
count: locals.count,
data: locals.docs
});
});
Just use JSON.parse:
exports.findAll = function(req, res, next) {
var locals = {},
section = req.params.section,
query = req.query,
filter = {};
if(query.filter) {
filter = JSON.parse(query.filter);
}
delete query.filter;
...
Hi I have this code but when finish the result is not the espected because didn't run in the sequence that I wish
here is the code:
var user_data = {};
models.games.find({$or: [{w_id: req.user._id}, {b_id: req.user._id}, {owner: req.user._id}]}, function (err, games) {
var req_games = [];
if (!err) {
for (var i in games) {
req_games.push(games[i]);
models.users.findOne({_id: games[i].w_id}, function (err, user) {
req_games[i].w_id = user.user;
console.log(req_games[i].w_id) //< -- 3
});
console.log('a ' + req_games[i].w_id) //<-- 2
}
user_data.games = req_games; // <-- 1
}
});
at the end of the task req_games didnt have any update because it's running in the sequence that I put in the comments in the code
This may help you using Q(promises)
obj.find = function(model, condition) { //make your find to return promise
var deferred = q.defer();
model.find(condition, function(err, results) {
if (err) {
logger.log(err);
deferred.reject(err);
} else {
deferred.resolve(results);
}
});
return deferred.promise;
}
ArraysOfId.forEach(function (id) {
var tempProm = mongoUtilsMethodObj.find(schemaObj.Asset, id).then(function (assetObj) {
---- your code
return q.resolve();
});
promArr.push(tempProm);//push all promise to array
});
q.all(promArr).then(function () {
// this will be called when all promise in array will we resolved
})
Here is a version using the async library to map your game values.
var async = require('async');
var user_data = {};
models.games.find({$or: [{w_id: req.user._id}, {b_id: req.user._id}, {owner: req.user._id}]}, function (err, games) {
if(err) {
// or whatever your error response happens to be
return res.render('user.swig', {error: err});
}
async.map(games, function(game, nextGame) {
models.users.findOne({_id: game.w_id}, function (err, user) {
game.w_id = user.user;
nextGame(err, game);
});
}, function(err, req_games) {
user_data.games = req_games;
res.render('user.swig', {user: user_data});
});
});
While building a fairly complex scraper i stumbled upon a problem with a control flow of my code.
What's going on in code below:
1) request a URL
2) scrape NEWURL from the results
3) pass it to readability API as first async function
4) here comes the trouble — i never get the next async function which saves readabilityData to DB
How to solve this problem?
I'm new to JS, so please feel free to point out at any issues with my code.
request(URL, function(error, response, html) {
if (!error) {
var $ = cheerio.load(html);
NEWURL = data.find('a').attr('href');
readabilityData = {}
var articleUrl = 'https://readability.com/api/content/v1/parser?url=' + NEWURL + token;
async.series([
function(){
request(articleUrl, function(error, response, html) {
if (!error) {
readabilityData = response.toJSON();
}
});
},
function(readabilityData){
Article.findOne({
"link": url // here's the
}, function(err, link){
if(link) {
console.log(link)
} else {
var newArticle = new Article({
// write stuff to DB
});
newArticle.save(function (err, data) {
// save it
});
}
});
}
],
function(err){
console.log('all good — data written')
});
});
}
});
You need to call the callback parameter that's passed into the functions of the async.series call when each function's work is complete. That's how async.series knows that it can proceed to the next function. And don't redefine readabilityData as a function parameter when you're trying to use it to share data across the functions.
So something like:
var readabilityData = {};
async.series([
function(callback){
request(articleUrl, function(error, response, html) {
if (!error) {
readabilityData = response.toJSON();
}
callback(error);
});
},
function(callback){
Article.findOne({
"link": url // here's the
}, function(err, link){
if(link) {
console.log(link);
callback();
} else {
var newArticle = new Article({
// write stuff to DB
});
newArticle.save(function (err, data) {
// save it
callback(err);
});
}
});
}
],
function(err){
console.log('all good — data written')
});
When I run collection.find() in MongoDB/Node/Express, I need to return value for my array like this but iam in callback hell;
foursquare.getVenues(params,function(error, venues) {
if (!error) {
var places = [];
venues.response.venues.forEach(function(e) {
places.push(
{
obj_id:e.id,
name:e.name,
distance:e.distance,
here_now:req.collection.findById(e.id) //count- i want need this value
}
);
});
res.send(places);
}
});
You can try to use Async https://github.com/caolan/async#each
var async = require('async');
...
foursquare.getVenues(params, function (error, venues) {
if (!error) {
throw err;
}
var places = [];
async.each(venues.response.venues, function (e, callback) {
db.collection.findById(e.id, function (err, res) {
places.push({
obj_id: e.id,
name: e.name,
distance: e.distance,
here_now: res
});
callback()
});
}, function (err) {
if (err) {
console.log('A file failed to process');
} else {
console.log('All files have been processed successfully');
res.send(places);
}
});
});
or Using async.map
var async = require('async');
var createArray = function (e, cb) {
db.collection.findById(e.id,function(err,res){
var obj = {
obj_id: e.id,
name: e.name,
distance: e.distance,
here_now: res
}
cb(null, obj);
});
}
async.map(venues.response.venues, createArray, function (err, places) {
if(err){
throw err;
}
console.log(places);
});