code: public synchronized boolean has(String name, Scriptable start) {
          if (isEmpty(name)) {
              return indexedProps.containsKey(name);
          } else {
              synchronized (context) {
                  return context.getAttributesScope(name) != -1;
              }
          }
      }
docs: Returns true if the named property is defined.
  
  @param name the name of the property
  @param start the object in which the lookup began
  @return true if and only if the property was found in the object