How to ignore errors using async/await syntax in JavaScript Promise.all()

user_1396977 0
Viewed 7295

I am trying to run a for loop which queues a bunch of asynchronous requests. Once all the requests complete, 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 completed.

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?

promise async-await javascript
2 Answers

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.net/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.net/DerekL/mwkww7w9/

user_2838630

I tried running your example like this: https://jsfiddle.net/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']
user_28811120
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