javascript window open passing dynamic url parameters

Working in ColdFusion, I have a javascript function like this:

function switchyn(obj,id,karr,kval){
  ... some stuff about obj and id ....
  var fullurl = 'arch-update.cfm?karr='+karr+'&kval='+kval;
  window.open(fullurl);
 }

The window opens fine, but the parameters passed to it are “karr” and “kval”; what I want to pass are the values of karr and kval. I can’t figure out how to do that, and can’t find any information in an online search. Can this be done? And if so, how?