Subj : Re: Compacting JS source via ParseTree or Decompile
To   : Dan Libby
From : Brendan Eich
Date : Tue Jun 08 2004 07:48 pm

Dan Libby wrote:
> Okay, so clearly I do not yet understand how to iterate through a 
> script's functions and variables.  I came up with the following draft, 
> which at least compiles, but exits at the first for loop in 
> shorten_script_vars().  ida->length is always 0.  The object is the 
> Global class that was created for the context.

JS_Enumerate is for enumerable properties only.  Also, until you execute 
the script (or at least its prolog, see JS_ExecuteScriptPart), you won't 
see any properties defined by it in the object you passed in as the obj 
param when compiling it.

> // Iterate through vars in function
> void shorten_function_vars(JSContext* cx, JSFunction* fun) {
>     JSIdArray* ida = JS_Enumerate( cx, fun->object );
>     if( ida ) {
>         jsval* val;
>         int i;
>         for(i = 0; i < ida->length; i++ ) {
>             if( JS_TRUE == JS_GetElement(cx, fun->object, 
> ida->vector[i], val) ) {
>                 JSType type = JS_TypeOfValue(cx, *val);

You don't really need the value -- you rather want to munge the id.

And you will be using friend and (until we make more friend APIs) 
private APIs to do this.  So, you don't want JS_Enumerate, again.  You 
should instead loop from OBJ_SCOPE(fun->object)->lastProp following 
parent links until null, testing for getter == js_GetLocalVariable || 
getter == js_GetArgument.

> Yes, arguments could/should be renamed (assuming JS only supports 
> positional arguments).

Right, JS2 adds named parameter passing.

/be

.