Yes, Promise.all is the right approach, but you actually need it twice if you want to first fetch all urls and then get all texts from them (which again are promises for the body of the response). So you’d need to do Promise.all(urls.map(u=>fetch(u))).then(responses => Promise.all(responses.map(res => res.text())) ).then(texts => { … }) Your current code … Read more
Is there a method for clearing the .thens of a JavaScript Promise instance? No. Not in ECMAScript 6 at least. Promises (and their then handlers) are uncancellable by default (unfortunately). There is a bit of discussion on es-discuss (e.g. here) about how to do this in the right way, but whatever approach will win it … Read more
You can adopt either of two approaches … Convert then combine : var p1 = Promise.resolve($.getJSON(url_1, params_1)); // voila 1! var p2 = Promise.resolve($.getJSON(url_2, params_2)); // voila 2! var p3 = Promise.all([p1, p2]).then(…); Combine then convert : var p1 = $.getJSON(url_1, params_1); var p2 = $.getJSON(url_2, params_2); var p3 = Promise.resolve($.when(p1, p2)).then(…); // voila 1 … Read more
The origin of this error lies in the fact that each and every promise is expected to handle promise rejection i.e. have a .catch(…) . you can avoid the same by adding .catch(…) to a promise in the code as given below. for example, the function PTest() will either resolve or reject a promise based … Read more
Promise.all is all or nothing. It resolves once all promises in the array resolve, or reject as soon as one of them rejects. In other words, it either resolves with an array of all resolved values, or rejects with a single error. Some libraries have something called Promise.when, which I understand would instead wait for … Read more
Shortly, the order is preserved. Following the spec you linked to, Promise.all(iterable) takes an iterable as a parameter and internally calls PerformPromiseAll(iterator, constructor, resultCapability) with it, where the latter loops over iterable using IteratorStep(iterator). Resolving is implemented via Promise.all() Resolve where each resolved promise has an internal [[Index]] slot, which marks the index of the … Read more
Update: jQuery 3.0 has fixed the problems outlined below. It is truly Promises/A+ compliant. Yes, jQuery promises have serious and inherent problems. That said, since the article was written jQuery made significant efforts to be more Promises/Aplus complaint and they now have a .then method that chains. So even in jQuery returnsPromise().then(a).then(b) for promise returning … Read more
Yes, you can do that, and it will run the two asynchronous functions in parallel. You’ve just created a promise and thrown it away. However, this means that when the promise is rejected you won’t notice. You’ll just get an unhandledRejection eventually which will crash your process if not handled. Is this OK? How can … Read more
As you already hinted in your question, your code creates all promises synchronously. Instead they should only be created at the time the preceding one resolves. Secondly, each promise that is created with new Promise needs to be resolved with a call to resolve (or reject). This should be done when the timer expires. That … Read more
Update, you probably want to use the built-in native Promise.allSettled: Promise.allSettled([promise]).then(([result]) => { //reach here regardless // {status: “fulfilled”, value: 33} }); As a fun fact, this answer below was prior art in adding that method to the language :] Sure, you just need a reflect: const reflect = p => p.then(v => ({v, status: … Read more