There’s a nice clean way to to this with [].reduce. var chain = itemsToProcess.reduce(function (previous, item) { return previous.then(function (previousValue) { // do what you want with previous value // return your async operation return Q.delay(100); }) }, Q.resolve(/* set the first “previousValue” here */)); chain.then(function (lastResult) { // … }); reduce iterates through the … Read more
IMHO I think there’s a much clever (and elegant) way to do this with $q.all. Please take a look at the code below. I am assuming that you want to return the data at once with all the results aggregated on a big array. var myApp = angular.module(‘myApp’, []); myApp.factory(‘myService’, function ($http, $q) { return … Read more
Don’t use a queue and that boolean flag, just have one variable storing a promise representing all uploads. Also, your upload function should not take a Deferred object to resolve as an argument, but simply return a new promise. Then the addAnUpload becomes as simple as var allUploads = $q.when(); // init with resolved promise … Read more
You use reduce over the array to chain the promises together. There is no need make this recursive. // for angularjs: var Q = $q.when; var p = a.reduce(function(prev, el) { return prev.then(function(arr) { return makeRequest(el).then(function(res) { return arr.concat([res]); }); }); }, Q([]));
Q promises can be resolved with only one argument – a promise stands for one single value, not for a collection of them. Put them in an array explicitly if you need multiple values. For the multiple-parameter-callbacks, you can use .spread().
All the answers here are really complicated in my opinion. Kos has the right idea but you can shorten the code by writing more idiomatic promise code: function retry(operation, delay) { return operation().catch(function(reason) { return Q.delay(delay).then(retry.bind(null, operation, delay * 2)); }); } And with comments: function retry(operation, delay) { return operation(). // run the operation … Read more
Redgeoff, your own answer is the way I used to translate an array into a chained series of promises. The emergent de facto pattern is as follows : function doAsyncSeries(arr) { return arr.reduce(function (promise, item) { return promise.then(function(result) { return doSomethingAsync(result, item); }); }, $q.when(initialValue)); } //then var items = [‘x’, ‘y’, ‘z’]; doAsyncSeries(items).then(…); Notes: … Read more
Try not to create a single deferred, that could be rejected from multiple parts of your function, and which you would need to return at every exit point. Instead, code with separate promises, one for each branch of control flow you have. You can use Q.reject and the Q.Promise constructor – avoid the deprecated deferred … Read more
Since promises can only resolve once (to either fulfilled or rejected), the first resolution wins and any further calls will be ignored. From the docs: In all cases where a promise is resolved (i.e. either fulfilled or rejected), the resolution is permanent and cannot be reset. Attempting to call resolve, reject, or notify if promise … Read more
It depends a bit on what the conditions to skip are, what kind of operations you are doing, and how “useful” the whole thing is when the conditions failed. You might be able to use a smart rejection here to bring the message across. Otherwise, I believe the correct way to deal with this is … Read more