Subj : Is "arguments" an array or not in Rhino?
To   : netscape.public.mozilla.jseng
From : Larry Blair <rathje40@yahoo.com>
Date : Tue Apr 15 2003 12:32 pm

The following function works in spidermonkey, but not in Rhino:

function f(){
   var c = [].concat(arguments);
   return c;}
var x = f("A", "B");
die (x.length+"|"+x[0]+"|"+x[1]);

Spidermonkey results = 2|A|B
Rhino results = 1|[object Arguments]|undefined

Btw, the following variation works in Rhino.  Unfortunately, our 1900 
app files don't use it:

function f(){
   var c = [].concat([arguments[0], arguments[1]]);
   return c;}
var x = f("A", "B");
die (x.length+"|"+x[0]+"|"+x[1]);

.