Sort array based on asynchronous method

Question

I'm using Ionic Native to read files in the user device, but I need to sort them by modification date.

The method to read the files returns Promise<Entry[]>. To find out the modification date, I need to call Entry's getMetadata method which has the following signature:

getMetadata(successCallback: MetadataCallback, errorCallback?: ErrorCallback): void;

Then in the success callback I have access to the Metadata object which has the modificationDate property I need for sorting.

I'd appreciate any help I can get.

make all your asyncs, store them somewhere and sort after... — Alex Michailidis
– Alex Michailidis, Commented Feb 1, 2018 at 14:52
Promise.all(asyncCalls.map(() => new Promise((resolve, reject) => getMetadata((...args) => resolve(...args)) might be something like this — uladzimir
– uladzimir, Commented Feb 1, 2018 at 15:25

Bergi · Accepted Answer · 2018-02-01 16:29:52Z

1

You'd start by promisifying the getMetadata method:

function getMetadataPromise(entry) {
    return new Promise((resolve, reject) => {
        entry.getMetadata(resolve, reject);
    });
}

Then you can use it in your loop and await all metadata, after which you can sort the array by it:

readEntries().then(entries =>
    Promise.all(entries.map(entry =>
        getMetadataPromise(entry).then(metadata => {
            entry.metadata = metadata;
            return entry;
        })
    ))
).then(entries =>
    entries.sort((a, b) => a.metadata.num - b.metadata.num) // or whatever
).then(sortedEntries => {
    console.log(JSON.stringify(sortedEntries));
}, console.error);

answered Feb 1, 2018 at 16:29

Bergi

671k162 gold badges1k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

brunobastosg Over a year ago

I had to tweak it a little bit and add some typings but it worked, thank you!

Collectives™ on Stack Overflow

Sort array based on asynchronous method

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related