uploaded files should be iterable

Current upload implementation sets the target element files to an object that matches the type definition for FileList. JSDOM and browsers implement FileList extending from Array, allowing them to be iterable (for example, one can perform [...element.files]). With the current implementation, after performing the upload, the attribute is not iterable.

sandbox with a demonstration: https://codesandbox.io/s/blazing-sunset-l6izw

[vadimshvetsov]

At first I was tried to implement function for emulating FileList but it’s not possible with current FileList implementation in jsdom.

function createFileList(files) {
  const fileList = new FileList(); // Illegal constructor
  for (const [index, file] of files.entries()) {
    fileList[index] = file;
  }
  fileList.item = (index) => fileList[index];
  return fileList;
}

Thats because of this line. So I see no clean option to make files as FileList at now. Here is the issue in jsdom we can keep eye on.

About iteration I’m not sure although its convenient to use. FileList is not marked as iterable in specs. What do you think @kentcdodds about supporting iteration as Chrome and Firefox do but not Edge (there is a proof in comments of this answer)?

[vadimshvetsov]

Hi, @rbusquet! Thanks for describing a problem here.

I’d tried to implement from the start upload as a FileList as close as possible because it cannot be created and a readonly unfortunately. The only way to create FileList is with DataTransfer constructor which has no reliable node polyfill as I’ve found.

Your case looks common and I will think about how to make it works with another PR.