Subj : Re: How do I raise an exception?
To   : netscape.public.mozilla.jseng
From : Peter Paulus
Date : Tue Aug 02 2005 04:33 pm

Thomas Sondergaard wrote:
> It seems that returning JS_FALSE from a JSNative c-function just results 
> in an error. How do I raise an exception? Preferably of type Error.
> 
> I've found some prior posts that seems to indicate that JS_ReportError 
> should do this, but doesn't because of a bug.
> 
> Regards,
> 
> Thomas
Hello Thomas,

The documentation at http://www.mozilla.org/js/spidermonkey/apidoc/ 
doesn't say, but there are some public API calls for exceptions:

Look at jsapi.h

extern JS_PUBLIC_API(void)
JS_SetPendingException(JSContext *cx, jsval v);

I believe jsval can be any type of value: scalar or object.

In order to throw an object you create it first with JS_NewObject():

obj = JS_NewObject(cx, &ExceptionClass, NULL, NULL);
v = OBJECT_TO_JSVAL(obj);

Scalars could be created with JS_NewUCString() and JS_NewDouble(). 
Boolean and Integer can do not have to be created but can be converted 
with BOOLEAN_TO_JSVAL() and INT_TO_JSVAL.

ExceptionClass is defined in jsexn.c and defines the javascript 'Error' 
class. Of course you can throw any class by using the appropriate 
JSClass* parameter here.

You could try and subclass the javascript 'Error' object.

Note bene: To be honest, I haven't tried this (it is still on my todo list).

With kind regards,
Peter Paulus

.