Retrieve Uploaded File Size

I would like a way in JavaScript to retrieve the size of the file that was uploaded using File Vault. I think it would be beneficial to have the value as a property of the file object that gets passed as an argument to onFileUploaded. Being able to get it from somewhere else could work, too.
Is there any chance this is already an undocumented feature, or do you plan on adding it any time soon?

not yet possible. the file size is not accessible on the client side. it is only known on the server.