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TypeError: someobject.somefunction(...).then is not a function

I have created a utility function for getting the total size of the webtable using protractor and javascript.
this.getTableSize = function(tableElement, rowSelector, columnSelector){
return {
row: tableElement.all(rowSelector).count(),
column : tableElement.all(columnSelector).count()
}
};
However on using the same function , i am geeting the error:
tableActions.getTableSize(table,by.css("tr"),by.css("th")).then(function(obj){
console.log(obj);
})
The error which i am getting is :
TypeError: tableActions.getTableSize(...).then is not a function

You need to correct your method to handle the promises correctly.
I assume that tableElement.all(rowSelector).count() returns a promise else you will have to handle the callbacks;
this.getTableSize = function (tableElement, rowSelector, columnSelector) {
return Promise.all([tableElement.all(rowSelector).count(), tableElement.all(columnSelector).count()]).then(function(data) {
return {
row: data[0],
column: data[1]
}
})
};
tableActions.getTableSize(table, by.css("tr"), by.css("th")).then(function (obj) {
console.log(obj);
})
Promise.all does not return the array of resolved data with bluebird promises so use.
this.getTableSize = function (tableElement, rowSelector, columnSelector) {
return ableElement.all(rowSelector).count().then(function(c) {
return ableElement.all(columnSelector).count().then(function (c2) {
return {
row: c,
column: c2
}
})
})
};
tableActions.getTableSize(table, by.css("tr"), by.css("th")).then(function (obj) {
console.log(obj);
})

The reason your code is failing is because you are using .then() on a function that does not return a promise.
Here's an example of a working promise:
let promise1 = new Promise( (resolve, reject) => {
let dataReceivedSuccessfully = false;
if (dataReceivedSuccessfully) {
resolve('Data Available!');
}
if (!dataReceivedSuccessfully) {
reject('Data Corrupted!');
}
})
promise1.then( (success) => {
console.log(success);
}).catch( (err) => {
console.log(err);
})
You can use this in your code to return a resolve or reject, and then you will be able to use .then().
https://medium.freecodecamp.org/promises-in-javascript-explained-277b98850de

Promises not waiting for each other in my nodejs controller

I got 4 promises here, and I thought that it would run the first one, then wait until its finished, THEN run the next one, wait till finished and THEN run the next one etc..
But what happens here is that it runs all of them all at once and does not wait for anything to finish.
This is my promise chain:
//
// Run the promises
//
findBanks
.then(findReceipts)
.then(findExpenses)
.then(sendResult)
.catch(err => {
console.error(err);
console.log("getbankAccountReport ERR: " + err);
res.json({error:true,err})
});
This is the output from my console.log
=====findAllBank=====
=====findAllReceipt=====
=====findAllExpense=====
=====RESOLVE findAllBank=====
=====sendResult=====
=====RESOLVE sendResult=====
=====RESOLVE findAllReceipt=====
=====RESOLVE findAllExpense=====
Am I not understanding promises correct or?
Anyway here is my nodejs controller:
exports.getBankAccountReport = function(req, res) {
//
// Find all bank accounts
//
var bankModel = require('../models/bankModel');
var bankTable = mongoose.model('bankModel');
var bankArray = [];
var findAllBank = new Promise(
(resolve, reject) => {
console.log("=====findAllBank=====")
bankTable.aggregate([
...lots of mongo stuff...
],function(err, data) {
if (!err) {
bankArray = data;
console.log("=====RESOLVE findAllBank=====")
resolve(data);
} else {
reject(new Error('findBank ERROR : ' + err));
}
});
});
//
// Find the RECEIPT for each bank account
//
var receiptModel = require('../models/receiptModel');
var receiptTable = mongoose.model('receiptModel');
var receiptArray = [];
var findAllReceipt = new Promise(
(resolve, reject) => {
console.log("=====findAllReceipt=====")
receiptTable.aggregate([
...lots of mongo stuff...
], function (err, data) {
if (!err) {
receiptArray = data;
console.log("=====RESOLVE findAllReceipt=====")
resolve(data);
} else {
reject(new Error('findReceipts ERROR : ' + err));
}
});
});
//
// Find the EXPENSE for each bank account
//
var expenseModel = require('../models/expenseModel');
var expenseTable = mongoose.model('expenseModel');
var expenseArray = [];
var findAllExpense = new Promise(
(resolve, reject) => {
console.log("=====findAllExpense=====")
expenseTable.aggregate([
...lots of mongo stuff...
], function (err, data) {
if (!err) {
expenseArray = data;
console.log("=====RESOLVE findAllExpense=====")
resolve(data);
} else {
reject(new Error('findExpense ERROR : ' + err));
}
});
});
var sendResult = function(data) {
var promise = new Promise(function(resolve, reject){
console.log("=====sendResult=====")
res.json({error:false,
"bank":bankArray,
"receipt":receiptArray,
"expense":expenseArray})
console.log("=====RESOLVE sendResult=====")
resolve();
});
return promise;
};
//
// Run the promises
//
findAllBank
.then(findAllReceipt)
.then(findAllExpense)
.then(sendResult)
.catch(err => {
console.error(err);
console.log("getbankAccountReport ERR: " + err);
res.json({error:true,err})
});
}

You need to wrap your Promises in functions
var findAllBank = function() {
return new Promise(
(resolve, reject) => {
console.log("=====findAllBank=====")
bankTable.aggregate([
...lots of mongo stuff...
],function(err, data) {
if (!err) {
bankArray = data;
console.log("=====RESOLVE findAllBank=====")
resolve(data);
} else {
reject(new Error('findBank ERROR : ' + err));
}
});
});
});
When resolved, the next function in the chain will be called with the data passed in the resolve() function.
Do no confuse the Promise and the function that builds it
When you create a new Promise(executor), you instanciate a new object that will have two methods (functions of an object), .then(resolveCB [, rejectCB]) and .catch(rejectCB).
The aime is to know, whenever a process is done, if it was successful or if it failed, and the continue accordingly.
var myFirstPromise = new Promise(function executor(resolve, reject) { resolve('resolved'); });
In other words, those methods are used to continue your process once the promise defined by executor is settled. It can either get fulfilled and call the resolveCB callback (usingthen), or rejected and call the rejectCBcallback (using both then and catch). A callback (resolveCB or rejectCB) is a function, not a Promise itself, even if the callback might return a Promise.
myFirstPromise
.then(function resolveCB(result) { console.log(result); }) //you can use a 2nd callback for rejection at this point
.catch(function rejectCB(err) { console.log(err); });
myFirstPromise
.then(
function resolveCB(result) { console.log(result); } // if resolved
, function rejectCB(err) { console.log(err); } // if rejected
)
.catch(function rejectCB(err) { console.log(err); }); // NEVER forget the last catch, just my 2cents :)
We saw the inputs of .then() and .catch() but what about their return value? The both of them will return a new Promise. That's why you can chain the .then()'s and .catch()'s.
myFirstPromise
.then(function resolveCB1(result) { console.log(result); })
.then(function resolveCB2(result) { console.log(result); }) // console.log is called but result is undefined
.catch(function rejectCB1(err) { console.log(err); });
myFirstPromise
.then(function resolveCB3(result) {
throw 'I threw an exception'; // an exception is thrown somewhere in the code
console.log(result);
})
.then(function resolveCB4(result) { console.log(result); })
.catch(function rejectCB2(err) { console.log(err); }); // a promise in the chain get rejected or error occured
In the previous example, we see that our second .then() is hit but result is undefined. The promise returned by first .then() fullfiled but no value as been passed by the executor to the resolve callback resolveCB2. In the second case, an exception occured in resolveCB3, it gets rejected so rejectCB2 is called. If we want our resolve callbacks to receive an argument, we have to notify the exector. To do so, the simplest way is for the callbacks to return a value:
myFirstPromise
.then(function resolveCB1(result) {
console.log(result);
result += ' again';
return result;
})
.then(function resolveCB2(result) {
console.log(result);
return result;
})
.catch(function rejectCB1(err) { console.log(err); });
Now that's said, you've got all the pieces together for understanding a Promise. Let's try to sum it up in a cleaner way:
var myFirstPromise = new Promise(function executor(resolve, reject) { resolve('resolved'); })
, resolveCB = function resolveCB(result) {
console.log(result);
result += ' again';
return result;
}
, resolveLastCB = function resolveLastCB(result) {
console.log(result);
result += ' and again';
return result;
}
, justLog = function justLog(result) {
console.log(result);
return result;
}
;
myFirstPromise
.then(resolveCB)
.then(resolveLastCB)
.then(justLog)
.catch(justLog);
You can now chan them nicely, it's cool and all
myFirstPromise
.then(resolveCB)
.then(resolveCB)
.then(resolveCB)
.then(resolveCB)
.then(resolveCB)
.then(resolveCB)
.then(resolveLastCB)
.then(justLog)
.catch(justLog);
But what if your Promise chain 'really' changes and you need to get rid of myFirstPromise and start with resolveCB instead ? It's just a function, it can be executed but doesn't have any .then() or .catch() method. It's not a Promise. You can't do resolveCB.then(resolveLastCB), it will thow an error resolveCB.then( is not a function or something similar. You might think this is a gross mistake, I didn't call resolveCB and resolveCB().then(resolveLastCB) should work? Unfortunalty for those who thought about that, it's still wrong. resolveCB returns a string, some characters, not a Promise.
In order to avoid this kind of maintenance issue, you should know that the resolve and reject callbacks can return a Promise instead of a value. To do so, we'll use what's called the factory pattern. In simple words, the factory pattern is about instanciating new object using a (static) function instead of using the constructor directly.
var myFirstPromiseFactory = function myFirstPromiseFactory() {
/*
return new Promise(function executor(resolve, reject) {
resolve('resolved');
});
if you just need to resolve a Promise, this is a quicker way
*/
return Promise.resolve('resolved');
}
, resolveFactory = function resolveFactory(result) {
return new Promise(function executor(resolve, reject) {
result = result || 'I started the chain';
console.log(result);
result += ' again';
return resolve(result); // you can avoid the return keyword if you want, I use it as a matter of readability
})
}
, resolveLastFactory = function resolveLastFactory(result) {
return new Promise(function executor(resolve, reject) {
console.log(result);
result += ' and again';
return resolve(result);
});
}
, justLogFactory = function justLogFactory(result) {
return new Promise(function executor(resolve, reject) {
console.log(result);
return resolve(result);
});
}
;
myFirstPromiseFactory() //!\\ notice I call the function so it returns a new Promise, previously we started directly with a Promise
.then(resolveFactory)
.then(resolveLastFactory)
.then(justLogFactory)
.catch(justLogFactory);
// Now you can switch easily, just call the first one
resolveFactory()
.then(resolveLastFactory)
.then(justLogFactory)
.catch(justLogFactory);
justLogFactory('I understand Javascript')
.then(resolveLastFactory)
.then(justLogFactory)
.catch(justLogFactory);
Factory functions might come handy when iterating over an array. It might be used to produce an array of promise given an input:
var myFirstPromiseFactory = function myFirstPromiseFactory() {
/*
return new Promise(function executor(resolve, reject) {
resolve('resolved');
});
if you just need to resolve a Promise, this is a quicker way
*/
return Promise.resolve('resolved');
}
, resolveFactory = function resolveFactory(result) {
return new Promise(function executor(resolve, reject) {
result = result || 'I started the chain';
console.log(result);
result += ' again';
return resolve(result); // you can avoid the return keyword if you want, I use it as a matter of readability
})
}
, resolveLastFactory = function resolveLastFactory(result) {
return new Promise(function executor(resolve, reject) {
console.log(result);
result += ' and again';
return resolve(result);
});
}
, justLogFactory = function justLogFactory(result) {
return new Promise(function executor(resolve, reject) {
console.log(result);
return resolve(result);
});
}
, concatValues = function concatValues(values) {
return Promise.resolve(values.join(' '));
}
, someInputs = [
'I am an input'
, 'I am a second input'
, 'I am a third input'
, 'I am yet an other input'
]
;
myFirstPromiseFactory() //!\\ notice I call the function so it returns a new Promise, previously we started directly with a Promise
.then(resolveFactory)
.then(resolveLastFactory)
.then(justLogFactory)
.catch(justLogFactory);
// Now you can switch easily, just call the first one
resolveFactory()
.then(resolveLastFactory)
.then(justLogFactory)
.catch(justLogFactory);
justLogFactory('I understand Javascript')
.then(resolveLastFactory)
.then(justLogFactory)
.catch(justLogFactory);
// Using a factory functions to create an array of promise usable with Promise.all()
var promiseArray = someInputs.map(function(input) {
return justLogFactory(input);
});
Promise.all(promiseArray)
.then(concatValues)
.then(resolveLastFactory)
.then(justLogFactory)
.catch(justLogFactory);

Recursively calling asynchronous function that returns a promise

I'm trying to recursively call AWS's SNS listEndpointsByPlatformApplication. This returns the first 100 endpoints then a token in NextToken if there are more to return (details: AWS SNS listEndpointsByPlatformApplication).
Here's what I've tried:
var getEndpoints = function(platformARN, token) {
return new models.sequelize.Promise(function(resolve, reject) {
var params = {
PlatformApplicationArn: platformARNDev
};
if (token != null) {
params['NextToken'] = token;
}
sns.listEndpointsByPlatformApplication(params, function(err, data) {
if (err) {
return reject(err);
}
else {
endpoints = endpoints.concat(data.Endpoints); //save to global var
if ('NextToken' in data) {
//call recursively
return getEndpoints(platformARN, data.NextToken);
}
else {
console.log('trying to break out!');
return resolve(true);
}
}
});
});
}
I'm calling it with:
getEndpoints(platformARNDev, null)
.then(function(ret) {
console.log('HERE!');
}, function(err) {
console.log(err);
});
Problem is: the first call happens, then the recursive call happens, and I get the message trying to break out! but the HERE! never gets called. I've got something wrong with how my promises are returning I think.
Grateful for pointers.

The problem is that you try and resolve/reject partially completed query. Here is a complete working example with dummy service. I incapsulated the data grabbing into it's own recursive function and only do resolve/reject when i've completely fetched all the data or stumbled upon an error:
// This is the mock of the service. It yields data and token if
// it has more data to show. Otherwise data and null as a token.
var dummyData = [0, 1, 2, 3, 4];
function dummyAsyncCall(token, callback) {
token = token || 0;
setTimeout(function() {
callback({
dummyDataPart: dummyData[token],
token: (typeof (dummyData[token]) == 'undefined') ? null : (token + 1)
});
});
}
// Here is how you would recursively call it with promises:
function getAllData() {
//data accumulator is sitting within the function so it doesn't pollute the global namespace.
var dataSoFar = [];
function recursiveCall(token, resolve, reject) {
dummyAsyncCall(token, function(data) {
if (data.error) {
reject(data.error);
}
if (!data.token) {
//You don't need to return the resolve/reject result.
resolve(dataSoFar);
} else {
dataSoFar = dataSoFar.concat(data.dummyDataPart);
recursiveCall(data.token, resolve, reject);
}
});
}
return new Promise(function(resolve, reject) {
// Note me passing resolve and reject into the recursive call.
// I like it this way but you can just store them within the closure for
// later use
recursiveCall(null, resolve, reject);
});
}
//Here is the call to the recursive service.
getAllData().then(function(data) {
console.log(data);
});
Fiddle with me

That's because you dont need to return resolve/reject, just call resolve/reject when the recursive call completes. A rough code would look like this
var getEndpoints = function(platformARN, token) {
return new models.sequelize.Promise(function(resolve, reject) {
var params = {
PlatformApplicationArn: platformARNDev
};
if (token != null) {
params['NextToken'] = token;
}
sns.listEndpointsByPlatformApplication(params, function(err, data) {
if (err) {
reject(err);
}
else {
endpoints = endpoints.concat(data.Endpoints); //save to global var
if ('NextToken' in data) {
//call recursively
getEndpoints(platformARN, data.NextToken).then(function () {
resolve(true);
}).catch(function (err) {
reject(err);
});
}
else {
console.log('trying to break out!');
resolve(true);
}
}
});
});
}
(caution: this is just a rough code, may work or may not, but is to give a general idea)
I've added a code snippet below, to support this concept, and it works great, check it out.
i = 0;
$('#output').empty();
function pro() {
return new Promise(function(resolve, reject) {
if (i > 3) {
resolve();
return;
}
window.setTimeout(function() {
console.log(i);
$('#output').append(i).append('<br/>');
i += 1;
pro().then(function() {
resolve()
}).catch(function() {
reject()
});
}, 2000);
});
}
pro().then(function () { $('#output').append("now here"); })
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div id="output"></div>

All functions in Q.all block are not being promised

I have the following code below in a then block
The issue I'm facing is at the end when i do the res.json(optionData1) its not returning the fully completed js data object i.e. the output after the processData function is missing
Am i using Q.all in the correct way?
var processUserInfo = function(categoryToProcess, inputToProcess, optionComingIn) {
var d = Q.defer();
if (optionData1['option'] == optionComingIn) {
if (optionData1[categoryToProcess].hasOwnProperty(inputToProcess)) {
optionData1[categoryToProcess][inputToProcess]++;
} else {
optionData1[categoryToProcess][inputToProcess] = 1;
}
d.resolve(optionData1);
}
}
var processData = function(item, optionComingIn) {
var d = Q.defer();
return User.find(
{_id: item},
{gender: 1, country:1},
function(req, foundUser) {
processUserInfo('gender', foundUser[0]['gender'], optionComingIn)
.then(function(resolve,reject) {
d.resolve();
});
});
return d.promise;
}
Q.all(foundQ[0]['people'].map(function(item) { // Or Q.allSettled
processCounts(item['optionSelected']);
processData(item['userID'], item['optionSelected']);
}))
.then(function(){
res.json(optionData1); //Doesnt give me the full result
});
Thanks
UPDATE: Using the return method as in the answer below got everything working.

Here is code which may work - too much "unknown" in your code snippet to be sure
modified processData to return a promise that resolves when user.Find is done
added a return in the .map, so the promise returned by processData is waited on in Q.all
So ... here's the fixed code (processuserInfo unchanged so omitted form the answer)
var processData = function (item, optionComingIn) {
// return a promise to wait for
return Q.promise(function(resolve, reject) {
User.find({
_id: item
}, {
gender: 1,
country: 1
},
function (req, foundUser) {
processUserInfo('gender', foundUser[0]['gender'], optionComingIn);
resolve();
}
);
});
}
Q.all(foundQ[0]['people'].map(function (item) { // Or Q.allSettled
processCounts(item['optionSelected']);
return processData(item['userID'], item['optionSelected']);
// return added
}))
.then(function () {
res.json(optionData1); //Doesnt give me the full result
});

Why doesn't this test with promises pass?

I've stepped into wonderful world of Promises a few days ago and I was just thinking I was enlightened. Promises look simple but they can be confusing.
Could you please tell me why the following test doesn't pass?
var Promise = require('bluebird');
var expect = require('chai').expect;
var request = Promise.promisifyAll(require('request'));
describe('Promise', function() {
it('should work again', function() {
var final_result;
function first_promise() {
return new Promise(function(resolve, reject) {
resolve("http://www.google.com");
})
}
function second_promise() {
return new Promise(function(resolve, reject) {
resolve("This is second promise!");
})
}
function inner_async_request(url_from_first_promise) {
return new Promise(function(resolve, reject) {
return request.getAsync(url_from_first_promise).spread(function(response, content) {
final_result = content;
resolve(content);
})
})
}
return request.getAsync('http://127.0.0.1:3000/').spread(function(result, content) {
//do something with content and then return first_promise
console.log(content);
return first_promise;
})
.then(function(url) {
inner_async_request(url).then(function(result) {
console.log(result);
final_result = result;
})
return second_promise;
})
.then(function(result) {
// result should be "This is second promise!"
console.log(result);
// final_result should be google's html
expect(final_result).not.to.be.undefined;
})
});
});
Currently the error is: Unhandled rejection Error: options.uri is a required argument which should be received from first_promise, I guess?
By this test, actually, I want to understand how to use promises which depend on each other AND how to use promises as asynchronous functions inside promises -which should just work separately-.
Thank you

You need to call the functions to return promises, like
return request.getAsync('http://localhost:3000/').spread(function(result, content) {
//do something with content and then return first_promise
console.log(content);
return first_promise();
})
And in some cases you don't need to create new promises at all
for Eg.
function inner_async_request(url_from_first_promise) {
return request.getAsync(url_from_first_promise).spread(function(response, content) {
final_result = content;
return content;
})
}
Finally, to make your test work, you need to modify this as well
.then(function(url) {
// return
return inner_async_request(url).then(function(result) {
console.log(result);
final_result = result;
return second_promise(); // return second promise inside then
})
})
DEMO