Subj : Re: Is "arguments" an array or not in Rhino?
To   : Larry Blair <rathje40@yahoo.com>
From : Igor Bukanov <igor@fastmail.fm>
Date : Tue Apr 15 2003 11:39 pm

Larry Blair wrote:
> 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

In the current SM the result would be the same as in Rhino:
1|[object Arguments]|undefined

For details, see http://bugzilla.mozilla.org/show_bug.cgi?id=169795 but 
the bottom line is that EcmaScript standard states 2 things:

1. Array.prototype.concat should flatten only instances of Array.

2. arguments object is not Array instance

Thus the reason for the change in SM and Rhino.

Regards, Igor

.