We discovered today that just attaching an event listener to an xhr.upload will cause the browser to do an OPTIONS request.[1]
This is really annoying because if you want progress events for an upload, the server CORS configuration has to be configured to allow OPTIONS. We were going to add upload progress events to URLBinaryLoader, but this throws a monkey wrench into those plans. We’ll probably do it as a subclass and document a warning about using it... Harbs [1]https://stackoverflow.com/a/17057853
