Async: what is a good pattern to wait for all iterations of async.eachLimit to finish before moving on?

Created on 17 Apr 2019 · 4Comments · Source: caolan/async

question: bit new to async and have following code to download lots of files, 2 at about the same time

async.eachLimit(files, 2, async (file, callback) => {
     reportStep("downloading");
     console.log("async start: " + file.path);
     await addFile(file.path, file.size);
     console.log("async end: " + file.path);    
     callback();
 }) 
reportStep("completed")

Of course, "completed" quickly get's fired while async.eachLimit continues executing funcs.

What is a good way to wait for all the iterations to be done?

question

Source

avieru

All 4 comments

nvm, didn't read the docs close enough.

there is yet another callback param, ended up wrapping it up all up in a promise that i can await

function download(files) {
    return new Promise((resolve, reject) => {
async.eachLimit(files, 2, async (file, callback) => {
     reportStep("downloading");
     console.log("async start: " + file.path);
     await addFile(file.path, file.size);
     console.log("async end: " + file.path);    
     callback();
         }, (error) => {
            if (error){
                reject(error);
            } else {
                resolve();
            }
        })
    });
}

await download(files)

avieru on 17 Apr 2019

Side note, if you are using the prerelease of v3, you don't need the wrapper. eachLimit will return a promise if you don't pass the final callback.

hargasinski on 17 Apr 2019

👍1

hmm, I tried awaiting async.eachLimit but it wasn't working for some reason or another. Thats what prompted me to post here. I'll have to give it another shot.

avieru on 17 Apr 2019

👍1

Did you suceed? I'm facing the same - it simply doesnt wait for all iterations's promises to finish.