Yes, that did the trick! In addition, the database connection is a mandatory parameter to the procedure object in this case:
var XSProc = $.import( 'sap.hana.xs.libs.dbutils', 'procedures' );
XSProc.setTempSchema( <SCHEMA> );
var oConn = $.db.getConnection( );
var oProc = XSProc.procedure( <SCHEMA>, <NAMESPACE>, <PROCEDURE>, { connection : oConn } );
var oRes = oProc( <PARAMETERS> );
oConn.commit( );
Thank you very much for answering so fast!!