Q:

can I use JSONP on same domain

I have a RESTful web service and jquery plugin that talks to the service.  The domains are different so I've implemented JSONP and everything works fine. 
I'm just working on a couple of changes and have hosted my test client and test service onto localhost but my JSONP callbacks are no longer being called. 
here is my jquery call. 
var urlbase = 'http://localhost:8080';

$.getJSON(urlbase + '/Geography/Countries?callback=?',  function (results) {
    alert(results);
    // populate the country lookup
    $.each(results, function (key, value) {
        $('select#countrylookup')
          .append($('<option></option>')
          .attr('value', value. Code)    
          .text(value. Name));
    });

I know for a fact that the service is being called and results are being returned because my service breakpoints are being hit and I can see the request/response in fiddler/F12 tools. 
If (as I suspect) I need JSON for 'local domain' and JSONP for cross-domain what strategy do others employ when testing?  Obviously I don't want any if(domain==local) style code anywhere. 

A:

Update: Turns out that my problem lies within the VS2010 web server.  if I host the site in local IIS no problem at all.  Even using the original getJSON. 
I've had this running now a couple of days and all seems to be fine.  I never mentioned in my original question about the use of VS2010 and WebDev.WebServer40.exe which I probably should of. 
To answer the actual question: Yes, you can use JSONP on localhost.