building classNames from values, like npm's ClassNames

gistfile1.txt

function classes(){
  return [].filter.call(arguments, Boolean).map(function(a){
      return typeof a === "object" ?  
           (Array.isArray(a) ?
               cn.apply(0,a) :
               Object.keys(a).filter(function(k){return a[k];}).join(" ")) :
           a;
  }).filter(String).join(" ");
}