Subj : Re: question about javascript functions
To   : netscape.public.mozilla.jseng
From : Béatrice Philippe
Date : Tue Feb 08 2005 10:02 pm

what i'm doing is :
1. reading each function body
2. if a function contains some javascript statements my app doesn't want, my 
app modifies the javascript function body  (that's what i try to).

The purpose is :
when my app changes the body of a javascript function, this function must be 
called everywhere and works.

I tried this example  :
here are two functions :
function fun1() {
 var i = 'hello';
 return i.toString();
}

function fun2() {
 var j = 'hello from fun2';
  var x = fun1();
 return x.toString();
}
somwhere in the html document:
<A href=..... onclick="javascript:fun1();".....>
if we do : 'js_evaluateScript()' for the onclick event: it works.

now, my app wants to change fun1 like this:
JSstring aBody = js_decompileFunctionBody(...);
char * aBody_char = js_GetStringBytes(...aBody);
..... here we change the content of aBody_char....
JSFunction *new_fun = js_compileFunction(contextOfGlobalObject, 
GlobalObject, aBody_char, strlen(aBody_char),.....);
 JSObject * childObject = JS_GetFunctionObject(new_fun);
 JS_AddRoot(contextOfGlobalObject,&childObject);

 jsval rval = OBJECT_TO_JSVAL(childObject);
JSObject *clonedFunc = JS_CloneFunctionObject(contextOfGlobalObject, 
childObject, GlobalObject);
 JS_DefineProperty(contextOfGlobalObject, GlobalObject, "fun1",
                         OBJECT_TO_JSVAL(childObject), nsnull, nsnull,
                         JSPROP_ENUMERATE | JSPROP_PERMANENT));

here, the function fun1 has been changed. Now, We can' t use 
js_evaluateScript() anymore to play the 'onclick' event, but we must use 
js_callFunctionValue() (or js_callFunction()) to call fun1 (and for that, we 
must know that the onclick event is a function call :-)). This solution 
works.

BUT: if we want to call fun2 function: it crashes since fun1 has changed and 
spidermonkey cannot resolve
 "x=fun1()" statement in fun2. Why ????? pointer lost ?
if we don't change fun1 body, calling fun2 works well ! strange !!!!

Any idea ?
Thank you.
-- 
Béatrice Philippe-Derbez
"Ludovic Delabre" <nowhere@nomail.lol> a écrit dans le message de news: 
42091608$0$532$626a14ce@news.free.fr...
>
> Béatrice Philippe wrote:
>> yes, your example is working !
>> but i'm trying to do this in my C++ application, using jsapi. And here is 
>> the problem...
> Yeah I understood you wanted to play with jsapi but I first needed to get 
> your problem... :-p
>
>>
>> I'm interrested in modifying the body of an existing javascript function 
>> in its global object.
> I just played a bit with jsapi using JS_CompileFunction() to dynamically 
> changes a function at runtime and ... no problem !?
> BTW, it also works fine for me without calling deleteProperty()...
>
>> So for the moment, i'm currently trying to delete my old function 'fun1' 
>> with 'js_deleteProperty()' in the global object, and then i create a new 
>> function with 'js_compileFunction()' method with the same name 'fun1'.
>> If my application tries to call the new fun1 with 'js_callFunction..()', 
>> it's working. But if the new fun1 function is called by others existing 
>> functions, it crashes.
>> I think when i try to delete a function fun1 with 'js_deleteProperty()', 
>> all functions that referenced this function fun1 are not notified about 
>> this change. They don't know fun1 was deleted and replaced by a new fun1 
>> function.
> From what I know, there're no hidden reference lying around, everythin' is 
> evaluated at runtime (but I might be mistaken?).
>
>>
>> My question is:
>> is there any way to change dynamically the body of an existing function 
>> in a C++ application, using jsapi ?
>> or if no, is there any solution to create a new function that would 
>> replace the old one ?
>
>> Thank you very much for your help.
> Well I don't know why it doesn't work for you when it works fine for me... 
> What are you doing exactly ?
>
> See ya,
> Ludovic.

.