How to cast/convert a browser FormData object to a Dart object, in Flutter Web?

Question

Basically I have a FormData object on the Javascript side in Flutter Web.

I need to send this object to Dart in order to make a http POST request, having the object's fields (including some eventual Blob/File field, as well) as the payload. The way I send this object to Dart is by registering a callback in Dart on the js.context window object, and calling that from the Javascript side.

Now, I've tried many different ways to achieve this:

• Get all it's fields using the spread operator, [...formData]
• JSON.stringify it and send it as a String
• JSON.stringify it's .entries()
• JSON.stringify it's keys() and values() individually
• some other work-arounds I found on the internet

I was able to send FormData's "simple" fields (String, number, Array, Object) BUT NOT FILE/BLOBs using theese approaches.

Is there any way to get that FormData object as a whole? That is, including the Files/Blobs it might contain, if any.

Thanks