I'm trying to upload an array of files to an s3 bucket. I'm building an array of promises for each file, that generates the pre-signed URL, blobs the file and then does the upload. Each promise should resolve once the upload is complete.

When all the uploads are complete, I try to refresh the page.

I'm attempting to do this with the following code:

async function uploadFiles() {
  let requestArray = files.map(file => {
    return new Promise(resolve => {
      handleDocs.GenerateUrl(file.fileName, "{!OppName}", async (result, event) => {
        let preSignedUrl = result.Data.toString().replace(/amp;/gm, "");
        let blob = b64toBlob(file.fileString, result.ContentType);

        await fetch(preSignedUrl, {
          method: "PUT",
          body: blob,
          headers: {
            "Content-Type": result.ContentType,


  await Promise.all(requestArray);

Where handleDocs.GenerateUrl is calling:

     Public static UploadUrl GenerateUrl(string NewFileName, String OpportunityName){
        NewFileName = NewFileName.deleteWhitespace();

        String getEndpoint = ApiUrl + '/document'
            + '?OpportunityName='+ EncodingUtil.urlEncode(OpportunityName, 'utf-8')
            + '&FileName='+ EncodingUtil.urlEncode(NewFileName, 'utf-8');

        HttpRequest request = new HttpRequest();
        request.setHeader('x-api-key', ApiKey);
        request.setHeader('Content-Type', 'application/json');

        Http http = new Http();

        HTTPResponse response = http.send(request);

        return (UploadUrl)JSON.deserialize(response.getBody(), UploadUrl.class);

My guess is that the handleDocs.GenerateUrl is behaving in a way that I don't understand, and I'm wiring the promises up incorrectly.

I've not been able to find any examples that solve a similar problem and that have worked for me.

The actual logic seems fine since the files do upload successfully most of the time. Is there any issue with how I'm building up the promises?

Any help would be appreciated!


I think I've figured out the cause and solution; I just misinterpreted what was going on with the promises.

This turned out to be caused by some of the other stuff on the page we were working on.

Part of the functionality we had was the ability to delete documents from S3, which is done with a call to an API we've written.

As part of our testing, we'd upload a file, delete it and then re-upload it, which is when we would see this issue.

As it turns out, document.location.reload(); is resubmitting the delete data as part of the page reload. Changing this to window.location.href = window.location.href; fixed the problem we were having. Doesn't seem to be anything wrong with how the promises were being handled, so apologies for the misleading question.

Thanks for the help!

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