Subj : Re: Seeking clarification on effect of literal vs. object syntax.
To   : netscape.public.mozilla.jseng
From : Christopher M. Balz
Date : Fri Aug 26 2005 04:46 pm

Thanks -- perfectly clear now.  

The reason I wondered is that I was not sure what the
word 'literal' meant in context.  In other words, I
was not sure if the 'literal' form of an array, etc.
was like a String literal, which is a primitive
(passed by value, not by reference, etc).  Thus I
wondered if this supposed 'primitive' was used to
construct an object on the fly.

All said and done, I'll take some sugar with my
Java(Script)! :)

  - Chris 


--- Brendan Eich <brendan@meer.net> wrote:

> Christopher M. Balz wrote:
> > Thank you for your response.  
> > 
> > The ECMA-262 spec is quite clear about RegExps, so
> I
> > read you that arrays and objects work the other
> way (a
> > fresh object is created each time the variable
> holding
> > the literal expression is evaluated).  
> 
> No, what you just wrote in parentheses is *not* what
> I wrote, and it's 
> incorrect.
> 
> You just wrote that
> 
>    var a = [1, 2, 3];
>    for (var i = 0; i < 100; i++)
>      print(a);
> 
> creates an Array object for each evaluation of the
> variable a in the 
> actual argument expression passed to print.
> 
> I said, and ECMA specifies, that the array
> initialiser [1, 2, 3] is 
> shorthand for new Array(1, 2, 3).
> 
> 
> > Wouldn't a program that had to constantly wrap
> array
> > literal variables in objects run much slower than
> one
> > that had made its arrays (for example) via the
> 'new
> > Array()' constructor call?
> 
> I'm not sure why you thought each expression using a
> variable that 
> happens to *refer* to an object created by an array
> or object 
> initialiser re-evaluates the initialiser, but that
> isn't how JS works, 
> and it doesn't make sense.  For one thing, objects
> are reference types, 
> so just evaluating a reference creates no new
> object.
> 
> /be
> 


Christopher M Balz
http://treelogic-swe.com
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94301-2437, USA
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chris@treelogic-swe.com
 
". . . / This Cabinet is formd of Gold / And Pearl & Crystal shining bright And within it opens into a World / . . . 
Another England there I saw / Another London with its Tower Another Thames & other Hills / And another pleasant Surrey Bower . . ." 
   - from "The Crystal Cabinet", a poem by William Blake.

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