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Promises with angularJS and Typescript

I have the following function, my goal is to push to the items list, when the components can identify their parent item.
The problem that I have is that when I am pushing to the list console.log() shows me that the object is in there, but when I return the list and catch it in another function, there is nothing in the list.
I think that the items list is returned before the code above it is done.
private get_items_for_request() {
return this.Item.forRequest(this.request.id, ['group'])
.then((_items) => {
var items = [];
for (var item of _items) {
return this.ItemComponent.forItem(item.id, ['type'])
.then((_components) => {
for (var component of _components) {
if (component.type.can_identify_item) {
items.push({
group_id: item.group.reference,
identifier_code: this.remove_check_digit_if_necessary(
component.identifier_code),
quantity: 1
});
break;
}
}
}, (reason) => {
this.Toast.error(
this.gettextCatalog.getString('components.load_failed'));
return [];
});
}
return items;
}, (reason) => {
this.Toast.error(
this.gettextCatalog.getString('items.failed_load'));
return [];
});
}

I'm afraid the trouble is with your approach, not with the code itself. A promise is just that - a promise of data some time in future. So, when you function returns (immediately), the promise is not resolved yet and the data your caller function captures is still empty. I don't see console.log() in your code, but would suspect you put it somewhere inside then(), which will be called once data has been received. So you will see data being logged. Trouble is by that time get_items_for_request() has already returned and your caller function has already moved on.
If you want to use a promise, you have to use a callback to be called once promise is resolved. But if you want actual data returned to the caller you need to fetch data synchronously.
For the synchronous fetch, check this response. But beware that synchronous fetch will hurt responsiveness of your script.
For an asynchronous fetch (using promises), you need to define a callback called once all data has been fetched. I won't try to fix your code, but it should go along the following sketch in javascript. Though keep in mind it's just a sketch.
function get_items_for_request(onSuccess) {
var items = []
var total = -1
var sofar = 0;
this.Item.forRequest(this.request.id, ['group'])
.then(function (_items) {
var items = [];
total = _items.length // remember how many nested calls will be made
for (var item of _items) {
this.ItemComponent.forItem(item.id, ['type'])
.then(function (_components) {
// push received data to the items array here
sofar++
if (sofar == total) { // all done
onSuccess(items)
}
}
}
}
}

In the first promise callback, you have two returns, only the first one runs. You return a promise after the first for, which you resolve to undefined. You should wait for an array of promises, each corresponding to a this.ItemComponent.forItem call.
Promise.all helps with this: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/all
You should do something like this:
return this.Item.forRequest(this.request.id, ['group']).then((_items) => {
return Promise.all(_items.map(function (item) {
return this.ItemComponent.forItem(item.id, ['type']).then((_components) => {
for (var component of _components) {
if (component.type.can_identify_item) {
return {
group_id: item.group.reference,
identifier_code: this.remove_check_digit_if_necessary(
component.identifier_code),
quantity: 1
};
}
}
}, (reason) => {
this.Toast.error(
this.gettextCatalog.getString('components.load_failed'));
return [];
});
}));
}, (reason) => {
this.Toast.error(
this.gettextCatalog.getString('items.failed_load'));
return [];
} )
If you only want one item, find the first non-falsy element in the resulting array

Modify list of objects via WebService, how to get final Value List?

I get data from a web service, I need to send this data to another service to modify some values, so when I get the data there are more async calls to make. I don't know how to get the final values.
What I want to call:
SomeService.getSomething(id).then(function(something) {
SomeOtherService.addXToDatas(something.data).then(function(fixedData) {
$scope.data = fixedData;
});
});
What I have:
someOtherService.addXToDatas = function(datas) {
datas.forEach(function(value, index, array) {
getSomethingFromApi(value.something).then(function(bla) {
array[index] = bla;
});
});
}
someOtherService.addXToData = function(data) {
getSomethingFromApi(data.something).success(function(response) {
order.someMore = response.data;
});
}
}
Unfortunately I have no actual clue how to accomplish this in javascript.
For a single object I could use a callback, but for a list of objects?

Angular.js has build-in implementation of Q, so you could use promise combination Q.all. It takes array of promises and returns a promise that is fulfilled when all other promises are.
You can easily create array of promises with Your code using .map instead of .forEach:
someOtherService.addXToDatas = function(datas) {
return $q.all( datas.map(function(value, index, array) {
return getSomethingFromApi(value.something).then(function(bla) {
array[index] = bla;
});
})).then(function() {
return datas;
});
}
SomeOtherService.addXToDatas(something.data).then(function(fixedData) {
$scope.data = fixedData;
});
Explanation:
datas.map() creates an array of promises. API calls themselves will be executed asynchronously.
$q.all() returns a promise which is fulfilled when all promises passed to it from (1) are fulfilled.
Final then returns modified data array. It is called after all promises from (1) are fulfilled and all modifications of data are made.

If I understand you correctly you want an array filled with data from the async calls in addXToDatas, you can do that like this:
someOtherService.addXToDatas = function(datas) {
var promises = [];
datas.forEach(function(value, index, array) {
promises.push(
getSomethingFromApi(value.something)
);
});
return $q.all(promises);
}
And in your controller:
someOtherService.addXToDatas([data1, data2,data3])
.then(function(resultArray) {
console.log(resultArray);
});
$q.all(promises) will return an array (in order) with the values of the promises. More info about $q and $q.all here.

Imbricated promises

What I want to do : get a list of projects (from API), request the status for each project. And call a callback who should represent the global status of my projects.
How I am trying to do it : the first promise get all projects and in the first then I am trying to call for each project a getProjectStatus who should get the status. I want that my second then wait that I finished the iteration (I tried many different things, but my second then is always called before). I don't know if this is a good using of promises...
var that = this;
var options = { url : this.host + "projects", json : true }
var finalStatus = "SUCCESS";
// first promises
return request(this.options)
.then(function(projects) {
projects.forEach(function(element, index, array) {
// second promises
that.getProjectStatus(element.id, function(status){})
.then(function(status) {
if(status != "SUCCESS)
{
finalStatus = "FAILURE";
}
});
})
})
.then(function(){
callback(finalStatus)});

This should get you going. You just use Promise.all on the array of second promises. I may not have understood the exact syntax of getProjectStatus but you can adjust I hope if needs be
return request(this.options)
.then(function(projects) {
return Promise.all( projects.map(element => that.getProjectStatus(element.id) )
.then(function(){
callback(finalStatus)});

How to wait for AsyncRequests for each element from an array using reduce and promises

I'm new on AngularJS and JavaScript.
I am getting remote information for each of the elements of an array (cars) and creating a new array (interested prospects). So I need to sync the requests. I need the responses of each request to be added in the new array in the same order of the cars.
I did it first in with a for:
for (a in cars) {
//async request
.then(function () {
//update the new array
});
}
This make all the requests but naturally didn't update the new array.
After seeking in forums, I found this great examples and explanations for returning a intermediate promise and sync all of them.
1. http://pouchdb.com/2015/05/18/we-have-a-problem-with-promises.html
2. http://stackoverflow.com/questions/25605215/return-a-promise-from-inside-a-for-loop
3. http://www.html5rocks.com/en/tutorials/es6/promises/
(#MaurizioIndenmark, #Mark Rajcok , #Michelle Tilley, #Nolan Lawson)
I couldn't use the Promise.resolve() suggested in the second reference. So I had used $q.defer() and resolve(). I guess I have to inject a dependency or something else that I missed. As shown below:
In the Controller I have:
$scope.interestedProspects = [] ;
RequestDetailsOfAsync = function ($scope) {
var deferred = $q.defer();
var id = carLists.map(function (car) {
return car.id;
}).reduce(function (previousValue, currentValue) {
return previousValue.then(function () {
TheService.AsyncRequest(currentValue).then(function (rData) {
$scope.interestedProspects.push(rData);
});
});
}, deferred.resolve());
};
In the Service I have something like:
angular.module('app', []).factory('TheService', function ($http) {
return {
AsyncRequest = function (keyID) {
var deferred = $q.defer();
var promise = authorized.get("somep.provider.api/theService.json?" + keyID).done(function (data) {
deferred.resolve(data);
}).fail(function (err) {
deferred.reject(err);
});
return deferred.promise;
}
}
}
The displayed error I got: Uncaught TypeError: previousValue.then is not a function
I made a jsfiddle reusing others available, so that it could be easier to solve this http://jsfiddle.net/alisatest/pf31g36y/3/. How to wait for AsyncRequests for each element from an array using reduce and promises
I don't know if the mistakes are:
the place where the resolve is placed in the controller function.
the way the reduce function is used
The previousValue and currentValue sometimes are seen by javascript like type of Promise initially and then as a number. In the jsfiddle I have a working example of the use of the reduce and an http request for the example.

Look at this pattern for what you want to do:
cars.reduce(function(promise, car) {
return promise.then(function(){
return TheService.AsyncRequest(car).then(function (rData) {
$scope.details.push(rData);
});
});
}, $q.when());
This will do all the asynchronous calls for every car exactly in the sequence they are in the cars array. $q.all may also be sufficient if the order the async calls are made doesn't matter.

It seems you are calling reduce on an array of ids, but assume in the passed function that you are dealing with promises.
In general, when you want to sync a set of promises, you can use $q.all
You pass an array of promises and get another promise in return that will be resolved with an array of results.

Promises for loop angular confused

I understand using promises in simple scenarios but currently really confused on how to implement something when using a for loop and some updates to local sqlite database.
Code is as follows
surveyDataLayer.getSurveysToUpload().then(function(surveys) {
var q = $q.defer();
for (var item in surveys) {
var survey = surveys[item];
// created as a closure so i can pass in the current item due to async process
(function(survey) {
ajaxserviceAPI.postSurvey(survey).then(function(response) {
//from response update local database
surveyDataLayer.setLocalSurveyServerId(survey, response.result).then(function() {
q.resolve; // resolve promise - tried only doing this when last record also
})
});
})(survey) //pass in current survey used to pass in item into closure
}
return q.promise;
}).then(function() {
alert('Done'); // This never gets run
});
Any help or assistance would be appreciated. I'm probably struggling on how best to do async calls within loop which does another async call to update and then continue once completed.
at least promises have got me out of callback hell.
Cheers

This answer will get you laid at JS conferences (no guarantees though)
surveyDataLayer.getSurveysToUpload().then(function(surveys) {
return Promise.all(Object.keys(surveys).map(function(key) {
var survey = surveys[key];
return ajaxserviceAPI.postSurvey(survey).then(function(response){
return surveyDataLayer.setLocalSurveyServerId(survey, response.result);
});
}));
}).then(function() {
alert('Done');
});

This should work (explanations in comments):
surveyDataLayer.getSurveysToUpload().then(function(surveys) {
// array to store promises
var promises = [];
for (var item in surveys) {
var survey = surveys[item];
// created as a closure so i can pass in the current item due to async process
(function(survey) {
var promise = ajaxserviceAPI.postSurvey(survey).then(function(response){
//returning this promise (I hope it's a promise) will replace the promise created by *then*
return surveyDataLayer.setLocalSurveyServerId(survey, response.result);
});
promises.push(promise);
})(survey); //pass in current survey used to pass in item into closure
}
// wait for all promises to resolve. If one fails nothing resolves.
return $q.all(promises);
}).then(function() {
alert('Done');
});
Awesome tutorial: http://ponyfoo.com/articles/es6-promises-in-depth

You basically want to wait for all of them to finish before resolving getSurveysToUpload, yes? In that case, you can return $q.all() in your getSurveysToUpload().then()
For example (not guaranteed working code, but you should get an idea):
surveyDataLayer.getSurveysToUpload().then(function(surveys) {
var promises = [];
// This type of loop will not work in older IEs, if that's of any consideration to you
for (var item in surveys) {
var survey = surveys[item];
promises.push(ajaxserviceAPI.postSurvey(survey));
}
var allPromise = $q.all(promises)
.then(function(responses) {
// Again, we want to wait for the completion of all setLocalSurveyServerId calls
var promises = [];
for (var index = 0; index < responses.length; index++) {
var response = responses[index];
promises.push(surveyDataLayer.setLocalSurveyServerId(survey, response.result));
}
return $q.all(promises);
});
return allPromise;
}).then(function() {
alert('Done'); // This never gets run
});