Question

I’m trying to pass large binary data (e.g. new Uint8Array(10000000)) from web page’s JavaScript (JS) to extension’s JS. I want these data to be saved from extension to a file by nsIBinaryOutputStream/nsIFile (which I can’t call from my page). [ATM I don’t know about any other method how to save (large/binary) data from page’s JS on local machine.]

I’ve red about an Interaction between privileged and non-privileged pages, but it is useful only for passing strings. I don’t think that converting 10MB from/to base64 is good idea.

• Is it even possible to pass such data to extension?
• If yes, how to do it then?
• Shouldn’t I use JS XPCOM component?

Thank you for suggestions.

Answer 1

OK, I’ve solved how to pass any object from webpage to extension.

In web page JavaScript (JS):

var element = document.createElement("foo");
document.documentElement.appendChild(element);
var event = document.createEvent("CustomEvent");
event.initCustomEvent("bar", true, false, anyObject);
element.dispatchEvent(event);

In extension JS:

document.addEventListener("bar", function(e) {
  // use e.detail here
 }, false, true);

Proof of concept here.