Open-source Back-end as a Service (BaaS)
In this test it's well exemplified how to do a file upload with Hook
https://github.com/doubleleft/hook-javascript/blob/23eb48e842ccf014e89daaea5890e733fa93f1db/tests/formdata.html#L53-L71
You can set a input[type=file] or a blob to a collection field. It will store the value as a file, and retrieve a URL to you.