Uploading files using HTML forms has always felt a bit off for me. You had to set your encoding to `multipart/form-data` and the synchronous nature of form posts always made it a waiting game when uploading larger files. Then came AJAX and the dawn of ”single page applications” and such buzzwords, but file uploads somehow got left behind. Javascript didn’t have the access it needed to send files with the `XMLHttpRequest`. Years passed and along came the File API and XMLHttpRequest Level 2 (it seems to be called that again) with its `upload` attribute, support for byte streams and progress events. Today I’m going to show you how to build an asynchronous file uploader with it. We’ll start with the HTML part: There’s nothing weird going on here; just a regular file selector and a list o…
