How to get MODx.panel.Template fields?

$modx->regClientStartupHTMLBlock('
        <script>
            Ext.onReady(function(){   
                var nameInput = Ext.get("modx-template-templatename");
                var staticFile = Ext.getCmp("modx-template-static-file");
                staticFile.setValue(nameInput.getAttribute("value") + ".tpl");
            });
        </script>');