source: Dev/trunk/src/client/dojo/tests/io/scriptJsonp.js

function getJsonpCallback(url){
        var result = null;
        var idMatch = url.match(/jsonp=(.*?)(&|$)/);
        if(idMatch){
                result = idMatch[1];
        }else{
                //jsonp didn't match, so maybe it is the jsonCallback thing.
                idMatch = url.match(/callback=(.*?)(&|$)/);
                if(idMatch){
                        result = idMatch[1];
                }
        }
        
        if(result){
                result = decodeURIComponent(result);
        }
        return result;
}

function findJsonpDone(){
        var result = false;
        var scriptUrls = getScriptUrls();
        
        for(var i = 0; i < scriptUrls.length; i++){
                var jsonp = getJsonpCallback(scriptUrls[i]);
                if(jsonp){
                        eval(jsonp + "({animalType: 'mammal'});");
                        result = true;
                        break;
                }
        }
        return result;
}

function getScriptUrls(){
        //Get the script tags in the page to figure what state we are in.
        var scripts = document.getElementsByTagName('script');
        var scriptUrls = new Array();
        for(var i = 0; scripts && i < scripts.length; i++){
                var scriptTag = scripts[i];
                if(scriptTag.id.indexOf("dojo_request_script") == 0){
                        scriptUrls.push(scriptTag.src);
                }
        }

        return scriptUrls;
}

function doJsonpCallback(){
        if(!findJsonpDone()){
                 alert('ERROR: Could not jsonp callback!');
        }
}

//Set a timeout to do the callback check, since MSIE won't see the SCRIPT tag until
//we complete processing of this page.
setTimeout(function(){doJsonpCallback();}, 300);