Bug with clearTimeout()?

Thank you.
I think I have asked my question in bad form.
I know about clearTimeout() without arguments.
But I call it with 1 argument. But the argument is undefined. And I see the same result. I do not know if it is a bug or not.
For example:

var timNum;
clearTimeout(timNum);
timNum=setTimeout(.....);

And I think it depends on JS implementation does on all devices, not only ESP8266. Usually I try to test my code for Puck.JS with ESP8266 first, because it is much easier to connect peripherals to it and to send code to it as well - espruino-server falls each second connection and can not work together with EspruinoHub.