Hi everyone. I only do JS for a couple of weeks now and could not find out, why the code

  this.show = function(username, cb) {
    var command = username ? "/users/"+username : "/user";

    _request("GET", command, null, function(err, res) {
      cb(err, res);
    });
  };

Works with

  ....show('dctr', myFunc);

and with

  ....show(myFunc);

Why doesn't command evaluate to something absurd and cb fails but myFunc is called in both cases? At least i would have expected something like

  cb = username ? cb : username;

Thanks in advance for anwers...