document.write('<script type="text/javascript" src="js/jquery.js"></script>');    

function using(js) {
    if(typeof js == "undefined") return false;
    
    if(typeof js == "string") {    
        if(js.search(",") != "-1") {
            var arr = js.split(",");
            for(var i = 0; i < arr.length; i++) {
                document.write('<script type="text/javascript" src="js/jquery.'+ $.trim(arr[i]) +'.js"></script>');    
            }
        } else {
            document.write('<script type="text/javascript" src="js/jquery.'+ $.trim(js) +'.js"></script>');    
        }        
    }    
}