var traverse = function(o, fn) {
  for (var i in o) {
    fn.apply(this,[i,o[i]]);  
    if (o[i] !== null && typeof(o[i])=="object") {
      traverse(o[i], fn);
    }
  }
}

// usage
var obj = {'your':'object'};
traverse(obj, function(k,v){
  console.log(k + " : " + v);
});