Subj : Re: Stuck with the basics
To   : Stu <stu.email@emailme.com>
From : Brendan Eich <brendan@meer.net>
Date : Thu May 22 2003 11:17 am


> char functionscript[4000];
>

You don't need to copy a string literal into a way-oversized array.

> char *argnames;
>

Should be const char *argnames[1]; or something like that.

>rt = JS_NewRuntime (10000000L);
>cx = JS_NewContext(rt, 8192);
>JS_SetErrorReporter(cx, my_ErrorReporter);
> glob = JS_NewObject(cx, &global_class, 0, 0);
> builtins = JS_InitStandardClasses(cx, glob);
>
>  /*
>   * Define an object named in the global scope that can be enumerated by
>   * for/in loops.  The parent object is passed as the second argument, as
>   * with all other API calls that take an object/name pair.  The prototype
>   * passed in is null, so the default object prototype will be used.
>  */
>  localobj = JS_DefineObject(cx, glob, "localObject", &its_class, 0,
>                          JSPROP_ENUMERATE);
> if (!JS_DefineProperties(cx, localobj, its_props))
>  return 1;
>
>strcpy (functionscript, "function Hello() {var hi = \"Hello World\"; return
>hi.toString();}");
>lineno = 0;
>
>functionptr = JS_CompileFunction(cx, glob, "Hello()", 0, &argnames,
>functionscript, strlen(functionscript), "default.pac", lineno);
>

You've just compiled a function whose *body* is 'function Hello() {var 
hi = "Hello World"; return hi.toString();}' -- in other words, you've 
just compiled a function Hello that contains another function named 
Hello, as if you typed this into the JS shell:

function Hello() {
  function Hello() {
    var hi = "Hello World";
    return hi.toString();
  }
}

> rval =0;
> executed = JS_CallFunction(cx, glob, functionptr, 0, jsargv, &rval);
>

You just called the outer Hello() and it returned undefined, because it 
contains no statements, only an inner function declaration.

>
>str = JS_ValueToString(cx, rval);
> JS_AddRoot(cx, &str);
>  printf("Call function script result: %s\n", JS_GetStringBytes(str));
>
>this prints Call function script result: undefined to the console.
>

That's the correct result.

/be

>
>
>
>  
>

.