function getobjectkey(obj,key,def)
{
 if (typeof(def)=='undefined') def='';
 val = obj.key;
 if (typeof(val)=='undefined') return def;
 return val;
}

function has_prop(obj,prop)
{
 if(typeof(obj[prop])=='undefined') return false;
 if(mytype(obj[prop])=='function')  return false;
 return true;
} 

function obj_get_prefix(obj,prefix)  
{
 var res={};
 for(var key in obj)
 {
  if (has_prefix(key,prefix)) res[key]=obj[key];
 }
 return res;
}