Passing data from promise then method to an object method - javascript

How to pass data from promise then method to an object method.
this.httpReq(url).then(function (data) {
this.storeData(data);
});
I know that here I'm out of scope and this doesn't refer to my object. But, nevertheless, I can't understand how to resolve it.
Bellow you can find entire code snippet. In the end, I want to get data from the service API and store it in the object array property this.storage.
var http = require('http');
function CoubApi (url) {
this.url = url;
this.storage = [];
this.httpReq = httpReq;
this.searchData = searchData;
this.storeData = storeData;
}
function httpReq (url) {
var promise = new Promise (function (resolve, reject) {
http.get(url, function (res) {
var data = '';
res.on('data', function (chunk) {
data += chunk;
});
res.on('end', function () {
if(data.length > 0) {
resolve(JSON.parse(data));
} else {
reject("Error: HTTP request rejected!");
}
});
}).on('error', function (err) {
console.log("Error: ", e);
});
});
return promise;
}
function storeData (data) {
var i;
console.log("Storrrreee");
for(i = 0; i < 10; i++) {
this.storage.push(data.coubs[i]);
}
}
function searchData (searchtext, order, page) {
var url = this.url+
"search?q="+searchtext+
"&order_by="+order+
"&page="+page;
this.httpReq(url).then(function (data) {
this.storeData(data);
});
}
var coub = new CoubApi("http://coub.com/api/v2/");
coub.searchData("cat", "newest_popular", 1);
console.log(coub.storage);

You can store this in varaible:
var self = this;
this.httpReq(url).then(function (data) {
self.storeData(data);
});
or use bind:
this.httpReq(url).then(function (data) {
this.storeData(data);
}.bind(this));

Related

Unable to return result from promise

I am trying to read some data from 2 different tables and parse a CSV file before rendering an ejs file.
I can get the data from both tables and from the CSV file but I seem to be unable to return the result.
Pretty sure this is a problem with the way I handle async execution but I fail to see what I am doing wrong.
I've spent the last 2 days reading about this (including the threads around here) and browsing but somehow the answer still escapes me.
First file - usercms.js
app.get('/userscms', function(req, res)
{
existingUsers.getExistingUsers()
.then(function(appUsers)
{
//global users array
//I can display these in my ejs file
globalAppUsers = appUsers;
})
.then(existingUsersAttributesQlik.getExistingUsersAttributesQlik())
.then(function(usersQlikAttributes)
{
//global user attributes array
//undefined data
globalUsersQlikAttributes = usersQlikAttributes;
})
.then(existingSuppliers.parseSuppliersCSV())
.then(function(supplierData)
{
//the result I am expecting
//this prints undefined
console.log(supplierData);
}).then(function()
{
res.render('userscms.ejs',
{
users: globalAppUsers,
attributes: globalUsersQlikAttributes
});
});
});
Second function - getxistingUsers.js (identical to the getExistingUsersAttributesQlik, except for the query)
var userData = [];
var appUsers = [];
(function (exports)
{
exports.getExistingUsers = function ()
{
return promisemysql.createConnection(dbconfig.development).then(function(conn)
{
var result = conn.query("SELECT id, username, firstName, lastName, email, phone, lastLogin, isAdmin, isValid, isPhoneValid, accountCreationDateTime FROM Users");
conn.end();
return result;
}).then(function(rows)
{
return rows;
}).then(function(rows)
{
if (rows.length)
{
userData = [];
appUsers = [];
rows.forEach(function (elem)
{
userData.push(_.toArray(elem));
});
for (i = 0; i < userData.length; i++)
{
var appUser = new appUserModel.AppUser(
userData[i][0],
userData[i][1],
userData[i][2],
userData[i][3],
userData[i][4],
userData[i][5],
userData[i][6],
userData[i][7],
userData[i][8],
userData[i][9],
userData[i][10]);
appUsers.push(_.toArray(appUser));
}
return appUsers;
}
else
{
console.log("NOPE");
return null;
}
}).then(function(appUsers)
{
console.log(appUsers);
return appUsers;
});
};
})(typeof exports === 'undefined' ? this['getExistingUsers'] = {} : exports);
Third file - parseSuppliersCSV.js
var supplierData = [];
var suppliersData = [];
var csvCount = 0;
(function (exports)
{
exports.parseSuppliersCSV = function ()
{
return new Promise(function(resolve, reject)
{
var fileStream = fs.createReadStream("myCSV.csv");
var parser = fastCsv();
csvCount = 0;
supplierData = [];
suppliersData = [];
fileStream
.on("readable", function ()
{
var data;
while ((data = fileStream.read()) !== null)
{
parser.write(data);
}
})
.on("end", function ()
{
parser.end();
});
parser
.on("readable", function ()
{
var data;
while ((data = parser.read()) !== null)
{
if(csvCount >= 1)
{
csvCount++;
var arrayOfStrings = data[0].split(';');
var supplier = new supplierModel.Supplier(arrayOfStrings[0],arrayOfStrings[1]);
suppliersData.push(_.toArray(supplier));
}
else
{
csvCount++;
}
}
})
.on("end", function ()
{
console.log("done");
//all OK here
console.log(suppliersData);
//this doesn't seem to return anything
return suppliersData;
});
});
};
})(typeof exports === 'undefined' ? this['parseSuppliersCSV'] = {} : exports);
Any ideas what I am doing wrong? Am I approaching this the wrong way?
I'll take a guess here and assume the promise you created should resolve to something...instead of returning a value.
.on("end", function ()
{
console.log("done");
//all OK here
console.log(suppliersData);
//this doesn't seem to return anything
return resolve(suppliersData);
});

Wait callback with Promise.mapSeries

I have a this:
new Promise(function (resolve, reject)
{
return Promise.mapSeries(array, function(field)
{
var objCb = {};
var params = {};
objCb.ok = function () {};
objCb.send = function (data)
{
errors.push(data.message);
};
objCb.negociate = function (err)
{
errors.push(data.message);
};
theFunction(params, objCb);
}
}
I have test multiple solutions, but don't work:
return Promise.promisify(theFunction(params, objCb), {multiArgs: true});
and
return Promise.fromCallback(function (objCb)
{
return theFunction(params, objCb);
}, {multiArgs: true}).spread(function (a)
{
console.log("==== 1");
console.log(a);
});
If you have a solution to wait a callback or convert into promise (without edit the function (theFunction)) in a mapSeries, I would be delighted to learn it.
Thanks in advance.
Promise.mapSeries returns a promise, so you don't need to re-wrap it.
Promise.mapSeries(array, function(field)
{
return new Promise( function(resolve, reject)
{
var objCb = {};
var params = {};
objCb.ok = function (resolve()) {};
objCb.send = function (data)
{
reject(data.message);
};
objCb.negociate = function (err)
{
reject(data.message);
};
theFunction(params, objCb);
}
}
Note: mapSeries will stop on the first error it encounters.

How return event emitter in node.js

I have this piece of code
module.exports = function(file, callback) {
var output, pdf, result, stderr;
output = '';
stderr = '';
result = [];
pdf = child_process.spawn('pdftotext', ['-layout', '-enc', 'UTF-8', file.name, '-']);
pdf.stdout.setEncoding('utf8');
pdf.stderr.setEncoding('utf8');
pdf.stdout.on('data', function(data) {
if (data) {
output += data;
}
});
pdf.stderr.on('data', function(data) {
if (data) {
stderr += data;
}
});
return pdf.on('close', function(code) {
var last_page, pages;
if (code !== 0) {
return stderr;
} else {
pages = output.split(/\f/);
if (!pages) {
return 'Nenhum texto foi encontrado';
}
last_page = pages[pages.length - 1];
if (!last_page) {
pages.pop();
}
file.text += pages;
return callback(file);
}
});
};
Basically I'm taking the text of PDFs using the pdftotext bash program.
This function is being called inside a Promise.map, so I need to return a new array of files, but before return, I need to call the callback, each will be responsible for other things.
The problem is: how can I return the pdf.on('close', funct....) ??
Inside it, I have the return callback(file); each is returning exactly what I want, but now I need return the same thing from pdf.on....
Thanks.
Your function, being asynchronous, should return a promise. Scrap that callback.
module.exports = function(filename) {
var output = '';
var stderr = '';
var pdf = child_process.spawn('pdftotext', ['-layout', '-enc', 'UTF-8', filename, '-']);
pdf.stdout.setEncoding('utf8');
pdf.stderr.setEncoding('utf8');
pdf.stdout.on('data', function(data) {
if (data) output += data;
});
pdf.stderr.on('data', function(data) {
if (data) stderr += data;
});
return new Promise(function(resolve, reject) {
//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pdf.on('close', function(code) {
if (code)
reject(new Error(stderr, code)); // call reject() for errors…
else
resolve(output); // and resolve() with the result *instead of that `callback`*
});
}).then(function(result) { // so that you then can chain processing to
var pages = result.split(/\f/);
if (!pages.length) {
throw new Error('Nenhum texto foi encontrado');
}
var last_page = pages[pages.length - 1];
if (!last_page)
pages.pop();
return pages.join("");
});
};
With that, you can easily use it as a proper Promise.map callback:
function phase_one(files) {
return Promise.map(files, function(file) {
return pdf(file.name).then(function(text) {
file.text = text;
return file;
});
}, {
concurrency: 3000
});
}

Concatenate several API request with NodeJS

I'm messing with SteamAPI in order to learn some NodeJS. Right now I'm trying to get games's info after an initial request to get the player's profile, once I have the games IDs stored in an array. The point is that I don't know how to "return" an array AFTER the whole ID array is iterated and all results has come from the server.
function getThumbs(game) {
return rq(
'http://store.steampowered.com/api/appdetails?appids=' + game,
{json: true},
function (error, response, bd) {
if(response.statusCode === 200 && bd[game].data) {
return bd[game].data.screenshots;
}
});
}
function getGamesThumbnails(games) {
var deferred = $q.defer(),
queue = [];
for (var y = 0; y < games.length; y++) {
var game = games[y];
var thumbs = getThumbs(game);
queue.push(thumbs);
}
$q.all(queue).then(
function (data) {
deferred.resolve(data);
},
function (err) {
deferred.reject(err)
}
);
return deferred.promise;
}
app.get('/blog',function(client_req,client_res){
rq('http://api.steampowered.com/IPlayerService/GetOwnedGames/v0001/?key=' + key + '&steamid=blablabla&format=json', function (error, response, body) {
var data = JSON.parse(body);
var games = data.response.games.map(function (game) {
return game.appid;
});
getGamesThumbnails(games).then(function (data) {
console.log(data)
})
});
});
Basically, you should use a callback, because like you are doing in getThumbsyou are returning the object, while you should return the value bd[game].data.screenshots;
function getThumbs(game, cb) {
return rq(
'http://store.steampowered.com/api/appdetails?appids=' + game,
{json: true},
function (error, response, bd) {
if(response.statusCode === 200 && bd[game].data) {
cb(null, bd[game].data.screenshots);
}
});
}
function getGamesThumbnails(games) {
var deferred = $q.defer(),
queue = [];
for (var y = 0; y < games.length; y++) {
var game = games[y];
getThumbs(game, function(err, value) {
queue.push(value);
});
}
$q.all(queue).then(
function (data) {
deferred.resolve(data);
},
function (err) {
deferred.reject(err)
}
);
return deferred.promise;
}
And plust to return the response to the client you have to use the client_res.send(VALUE)
so the bottom part would become like this:
app.get('/blog',function(client_req,client_res){
rq('http://api.steampowered.com/IPlayerService/GetOwnedGames/v0001/?key=' + key + '&steamid=blablabla&format=json', function (error, response, body) {
var data = JSON.parse(body);
var games = data.response.games.map(function (game) {
return game.appid;
});
getGamesThumbnails(games).then(function (data) {
client_res.send(data);
console.log(data)
})
});
});
Your getThumbs() function does not return a promise. $q.all only works on an array containing promises, whereas rq uses callbacks.
Try this:
function getThumbs(game) {
var deferred = $q.defer(),
rq(
'http://store.steampowered.com/api/appdetails?appids=' + game,
{json: true},
function (error, response, bd) {
if(response.statusCode === 200 && bd[game].data) {
deferred.resolve(bd[game].data.screenshots);
}
});
return deferred.promise;
}
Thank you both!
I tried Yuri's approach, but $q.all it doesn't seem to resolve the array of promises (nothing happens after the last request from getThumbs())
for (var y = 0; y < games.length; y++) {
var game = games[y];
var thumbs = getThumbs(game);
queue.push(thumbs);
}
$q.all(queue).then(
function (data) {
console.log(data)
deferred.resolve(data);
},
function (err) {
deferred.reject(err)
}
);

WinJS return in promise array

I have a problem with returning array in Winjs promise and I don't have any idea what is wrong with my code. When i create a promise and do .done or .then my promise does nothing.
Code :
function getSth(array) {
return new WinJS.Promise(function () {
var dbPath = Windows.Storage.ApplicationData.current.localFolder.path + '\\_db.sqlite';
var i = 0;
SQLite3JS.openAsync(dbPath)
.then(function (db) {
console.log('DB opened');
return db.eachAsync('SELECT * FROM sthh;', function (row) {
array[i++] = row.sth;
console.log('Get a ' + row.sth);
});
})
.then(function (db) {
console.log('close the db');
db.close();
}).then(function () {
return array;
});
return array;
})
}
And in other file I just do something like that :
var array = [];
var z = getSth(array).then(function () {
console.log("AAA");
for (var i = 0; i < array.length; console.log("#" + array[i]), i++);
});
I will be very gratefull for any suggestion.
I assume you don't want to return immediately and instead want to return the array once it is full of elements?
I think you want to write code that is more like this:
function getSth(array) {
var dbPath = Windows.Storage.ApplicationData.current.localFolder.path + '\\_db.sqlite';
var i = 0;
return SQLite3JS.openAsync(dbPath)
.then(function (db) {
console.log('DB opened');
return db.eachAsync('SELECT * FROM sthh;', function (row) {
array[i++] = row.sth;
console.log('Get a ' + row.sth);
});
})
.then(function (db) {
console.log('close the db');
db.close();
}).then(function () {
return array;
});
}

Categories