I am trying to run a for loop which queues a bunch of asynchronous requests. Once all the requests plete, independent of whether they resolve or reject, I want to then run some code. I am trying to take advantage of the async/await pattern, as it looks nicer. :)

This is what I am doing:

var promises = []
for ( item in list ) {
    prom = AsyncFunction( item )
    promises.push(prom)
}

await Promise.all(promises)

doMoreAfter()

However, some of the promises fail, and the second that happens Promise.all() fails aswell.

I want to simply ignore any failed promises, and have the next code run after all the promises have pleted.

I found solutions like this.

Promise.all([a(), b(), c()].map(p => p.catch(e => e)))
  .then(results => console.log(results)) // 1,Error: 2,3
  .catch(e => console.log(e));

But it doesn't look like it works when trying to turn it into the async/await format.

await Promise.all(promises.map(p => p.catch(e => e)))

What am I missing?

I am trying to run a for loop which queues a bunch of asynchronous requests. Once all the requests plete, independent of whether they resolve or reject, I want to then run some code. I am trying to take advantage of the async/await pattern, as it looks nicer. :)

This is what I am doing:

var promises = []
for ( item in list ) {
    prom = AsyncFunction( item )
    promises.push(prom)
}

await Promise.all(promises)

doMoreAfter()

However, some of the promises fail, and the second that happens Promise.all() fails aswell.

I want to simply ignore any failed promises, and have the next code run after all the promises have pleted.

I found solutions like this.

Promise.all([a(), b(), c()].map(p => p.catch(e => e)))
  .then(results => console.log(results)) // 1,Error: 2,3
  .catch(e => console.log(e));

But it doesn't look like it works when trying to turn it into the async/await format.

await Promise.all(promises.map(p => p.catch(e => e)))

What am I missing?

• javascript
• promise
• async-await

• Well, Promise.all() rejects as soon as the first promise you pass to it rejects so the ONLY way to make it wait for all promises to finish is to keep any promise you pass to Promise.all() from rejecting. When I want this type of behavior, I just use on of these Promise.settle() versions which gives you the desired behavior built-in to a utility function rather than hand coded separately each time. – jfriend00 Commented Nov 26, 2017 at 6:44

3 Answers 3

I feel like the best you can do is this:

var promises = [a, b, c];
promises = promises.map(p => p().catch(e => undefined));

values = await Promise.all(promises);
console.log(values);  // ["a", undefined, "c"]

https://jsfiddle/DerekL/h5Lmxaqq/

Or you can create an ignore function:

function ignore(promise){
    return promise.catch(e => undefined);
}

async function main(){
    var promises = [a(), b(), c()];

    var values = await Promise.all(promises.map(ignore));
    console.log(values);
}

https://jsfiddle/DerekL/mwkww7w9/

I tried running your example like this: https://jsfiddle/804ogadu/3/

var a = Promise.resolve('a');
var b = Promise.resolve('b')
var c = Promise.reject('errc');

async function test(){
const t = await Promise.all([a, b, c].map(p => p.catch(e => e)));
console.log(t);
}

test();

I do get the required result

['a,'b','errc']

Did you consider using Promise.allSettled()? (https://developer.mozilla/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/allSettled#using_promise.allsettled)