Not able to download multiple files from S3 pre-signed urls using JS

Question

Before I start with the question, I have gone through multiple stackoverflow answers around similar sort of questions (including those which have been asked and not answered till now). I have also gone through one of the medium articles. So, I have done a fair bit of research.

I have been trying to download multiple files using presigned urls. The code below was working few days back (this might sound familiar ;)) but currently, I am just able to download one file that too the download is random. Sometimes the first file is downloaded and sometimes the last. Code is provided below:

downloadItem() {
  let urls = [];
  for(let item of this.selectedRowsData) {
    //calling the service to fetch the presigned url
    this.dataService.getPresignedToDownloadAll(
      item.value,
      item.id).subscribe((res) => {
        urls.push(res);
        this.download(urls);
        /**if(urls.length === selectedRowData.length) {
           this.download(urls);
        }**/ //have tried this code too where I just invoke download only once when I have all the presigned urls
    });
 }
}
download(urls: any) {
  var self = this;
  var url = urls.pop();
  setTimeout(function(){
    self.snackBarService.loadComponent({
      isSuccess: true,
      message: MESSAGES.downloadInProgress,
    });
  var a = document.createElement('a');
  a.setAttribute('href', url);
  document.body.appendChild(a);
  a.setAttribute('download', '');
  a.setAttribute('target', '_self');
  a.click();
  // a.remove();
  }, 1000)
}

Any help is much appreciated.

Answer 1

I was not able to download the multiple images from presigned urls on the same browser tab which is what I was trying to do with a.setAttribute('target', '_self');

But I was able to make it work by setting target as _blank which does open up a new tab but closes those opened tabs once the download is done. Though this is not a great user experience but as of now we have gone ahead with this implementation. This is what the final code looks like

downloadItem() {
  let urls = [];
  for(let item of this.selectedRowsData) {
  //calling the service to fetch the presigned url
  this.dataService.getPresignedToDownloadAll(
    item.value,
    item.id).subscribe((res) => {
      urls.push(res);
      this.download(urls);
   });
 }
}

download(urls: any) {
  var self = this;
  var url = urls.pop();
  setTimeout(function(){
    self.snackBarService.loadComponent({
      isSuccess: true,
      message: MESSAGES.downloadInProgress,
    });
  var a = document.createElement('a');
  a.setAttribute('href', url);
  document.body.appendChild(a);
  a.setAttribute('download', '');
  a.setAttribute('target', '_blank');
  a.click();
 // a.remove();
 }, 1000)
}