A method for extending a script language in a runtime environment of a data processing system to support an application, the runtime environment having a script language interpreter, the method comprising: subclassing a predetermined object defined by the script language to create a subclassed object, the predetermined object having an original method, the subclassed object having a respective replacement method for supporting the application; dynamically registering a symbol corresponding to the subclassed object; detecting the subclassed object in the application with the script language interpreter; and, executing the replacement method with the script language interpreter.