if (typeof(km_scripts) == 'undefined') var km_scripts = new Object();
km_myclass_import("js/datepicker/ui.datepicker.js"); 
km_myclass_import("js/datepicker/ui.core.js"); 
km_myclass_import("js/datepicker/jquery.ui.datepicker-tr.js");

function km_myclass_import(jsFile) {
if (km_scripts[jsFile] != null) return;
var scriptElt = document.createElement('script');
scriptElt.type = 'text/javascript';
scriptElt.src = jsFile;
document.getElementsByTagName('head')[0].appendChild(scriptElt);
km_scripts[jsFile] = jsFile; // or whatever value your prefer
}