var callbacks = new Object();

function getJSONP(url,cb)
{
    var i;
    do
    i='c'+Math.floor(Math.random() * 99999);
    while(callbacks[i]);

    callbacks[i] = function(obj) {
                      cb(obj);
                      delete callbacks[i];
                    };

    var script=document.createElement('script');
    script.src=url+(url.indexOf('?')>=0?'&':'?')+'callback=callbacks.'+i;
    script.type='text/javascript';
    document.body.appendChild(script);
}