Subj : Re: Seeking clarification on effect of literal vs. object syntax.
To   : Christopher M. Balz
From : Brendan Eich
Date : Fri Aug 26 2005 02:58 pm

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

.