if(typeof(Sys)!=='undefined')             
                {                
                    if(typeof(Sys._ScriptLoader) !== 'undefined')
                    {                                    
                        Sys._ScriptLoader.isScriptLoaded = function Sys$_ScriptLoader$isScriptLoaded(scriptSrc) 
                        {                                                    
                            var dummyScript = document.createElement('script');
                            dummyScript.src = scriptSrc;
                            var result = Array.contains(Sys._ScriptLoader._getLoadedScripts(), scriptSrc);
                            if( result === true ) return true;
                            result = Array.contains( window._combinedScripts, scriptSrc );
                            if( result === true ) return true;                            
                            var scriptTags = document.getElementsByTagName('script');
                            for(var i = 0; i < scriptTags.length; i ++ ) if( scriptTags[i].src == dummyScript.src ) return true;
                            return false;
                        }
                    }                    
                }