In a-frame arjs how can I add/update a-marker pattern in runtime?

Question

I added some html buttons, and I want them to change the currently tracking a-marker-camera's pattern and track different marker. I tried accessing the a-marker-camera (in an iframe) like below and changed its url.

var marker = myFrame.contentWindow.document.getElementById("marker");
marker.setAttribute("url", this.patternUrl);

It did change the URL but it didn't really update and continue tracking the former one. Then I tried creating 'a-marker-camera' manually in runtime.

var ascene = myFrame.contentWindow.document.getElementById("scene");
            var newMarker =  myFrame.contentWindow.document.createElement("a-marker-camera");
newMarker.setAttribute("id", "marker");
newMarker.setAttribute("type", "pattern");
newMarker.setAttribute("url", this.patternUrl);
ascene.appendChild(newMarker);

Same as before, it did get added, and looked perfectly fine in source. But this one also didn't work. So I don't know what else I can try, or is this even possible?