Callback from Firemonkey WebBrowser JavaScript code

So in the URL you can pass a custom string or whatever data like this:

myurl://dostuff?a=b&c=d

if (Copy(S, 1, 8)='myurl://') then
begin
// now you know it is a callback and not a real URL
// if it is a callback you can cancel the load using the below code
// and then process the callback
end;

TWebBrowser:

procedure TForm2.WebBrowser1ShouldStartLoadWithRequest(ASender: TObject;
  const URL: string);
begin
// check URL and
WebBrowser1.Stop;
end;

TTMSFMXWebBrowser:

procedure TForm2.TMSFMXWebBrowser1BeforeNavigate(Sender: TObject;
var Params: TTMSFMXCustomWebBrowserBeforeNavigateParams);
begin
// Get your result from Params.URL and cancel via Params.Cancel := True;
end;