//
// GENERAL HELPERS
// - cross-browser object-type detection
function isUndefined(o) {
  return (typeof(o) == "undefined");
}
function isNull(o) {
  return (typeof(o) == "object" && o);
}
function isObject(o) {
  return (o && "object" == typeof(o)) || isFunction(o);
}
function isFunction(f) {
  return "function" == typeof(f);
}
function isArray(a) {
  return isObject(a) && a.constructor == Array;
}
function isRegExp(o) {
  return isObject(o) && o.constructor == RegExp;
}
function isString(o) {
  return typeof(o) == "string";
}
function isNumber(o) {
  return typeof(o) == "number";
}
function isBoolean(o) {
  return typeof(o) == "boolean";
}