Firebase Cloud Function: Problem With Promise.all(promise)

I loop throw a list of files in Firebase storage and I would like to modify a string while looping, Here is what I tried to do: var str; storage.bucket().file(...).download((er

Solution 1:

If it can be usefull for someone, here is the solution I found:

var promises = [];
var str="string containing data to replace with signed url";

storage.bucket().getFiles({ prefix: folderPath }).then(results => {
  const files = results[0];
  files.forEach(function(file) {

     promises.push( //the trick was here

       file.getSignedUrl(signedUrlConfig).then(signedUrls => {
         ...
         surl = signedUrls[0];
         str=str.replace("a",surl); //eg: replace with signed url.return str;
       });
     );
  });
  Promise.all(promises).then(() => {
    console.log(str); //str contains all signed url
  });
});

Solution 2:

It seems you are looking for

const promise = storage.bucket().file().download().then(str => {
//    ^^^^^^^^^                                   ^^^^^return storage.bucket().getFiles().then(results => {
//  ^^^^^^const files = results[0];
        for (const file of files) {
            …
            str = str.replace("t","a");
        }
        returnstr;
    //  ^^^^^^
    });
});

promise.then(str => { /*
^^^^^^^^^^^^ */
    console.log(str);
    return file.save(str); // should return a promise
});

You need neither new Promise nor Promise.all here. You might use the latter though to remove the nesting and potentially even run getFiles() and download() concurrently, see How do I access previous promise results in a .then() chain?.