Subj : Re: JS_IsAssigning
To   : jmtn@blueyonder.co.uk
From : Brendan Eich <brendan@meer.net>
Date : Thu Aug 28 2003 05:43 pm

James Turner wrote:

>Then I found JS_IsAssigning(), and I was happy, until I tried using
>it. The problem is, it never, ever returns 'true' for me, in either of
>the cases above (naturally, I'd expect it to return false for the
>first case, and true for the second). Have I misunderstood what is's
>supposed to do?
>

Yes, you've misunderstood (or the docs lie again).  JS is bytecoded, so 
the expression foo.bar.x = 42 is turned into postfix code of the form 
'name "foo"; getprop "bar"; uint16 42; setprop "x"'.  Only from the 
setprop bytecode would JS_IsAssigning return true.

> I also note that there's some JS_RESOLVE flags that
>mention assignment; are these something I could be investigating?
>

Only if you're resolving 'x' in foo.bar.  If you're resolving 'bar' in 
foo while evaluating 'foo.bar.x = 42', the resolve call for 'bar' in foo 
will not include the JSRESOLVE_ASSIGNING flag.

Why do you need to detect a difference when resolving or getting 'bar' 
in foo between 'baz = foo.bar.x;' and 'foo.bar.x = 42;'?

/be

.