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SPENDLOVE, Matt, FM

2005-Sep-22 09:08 UTC

[Rails-spinoffs] Prototype lib : for-each loops and DontEnum

All

I realise that this isn''t strictly the correct place to discuss the
prototype lib but being as scriptaculous is dependent on it I thought people
might have some opinions.

Easier to explain with the example below, copy into a html file and ensure
the path to prototype.js is correct. You''ll see the first example
prints an
extra element "extend" when iterating over the Array using a for-each
loop..

- Problem

In a nutshell, because prototype adds an extra member variable to the Object
type (extend), it kinda breaks the for-each loop (for x in y) for all
implicit js objects e.g. Array, presumable because they extend Object.

Some code we use (perhaps incorrectly) assumes all members within a custom
object are things that it''s interested in. The addition of the
"extend"
variable breaks things. 

We use Struts and it''s validator framework falls into this trap. 

- Solution

Well, it''s hacky but we skip members called "extend". Reading
the ECMAScript
spec and various things on the web (see links) I can see that the language
spec sets it''s own internal variables (e.g. length ) with a property
called
DontEnum which excludes them from a for-each. Unfortunately, there
doesn''t
seem to be an api to set this yourself :(

- Links

<http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf>
- ECMAScript Spec
<http://bclary.com/2004/09/26/boot-camp-javascript> - Excellent language
overview

Any thought / opinions or suggestions welcome.

Matt


----------------------------------------------------------------------------
------
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html;
charset=ISO-8859-1"
/>
	<meta http-equiv="imagetoolbar" content="no" />
	<title>:::: Test ::::</title>
	<!--
	<link rel="stylesheet" type="text/css"
href="style/polymorphic.css"
/>
	-->
</head>
<body>

<script src="javascript/prototype.js"
type="text/javascript"></script>
<!--
<script src="javascript/effects.js"
type="text/javascript"></script>
<script src="javascript/dragdrop.js"
type="text/javascript"></script>
<script src="javascript/controls.js"
type="text/javascript"></script>
-->
<script type="text/javascript">


document.writeln("<br /><br /> Array Test ");

var o = new Array("1","2","3");

document.writeln("<br /><br /> test array contents =
["+o+"]");

document.writeln("<br /> c style for loop");
for (var i = 0; i < o.length; i++)
{
	document.writeln("<br /> i["+i+"] =
["+o[i]+"]");
}

document.writeln("<br /> for each loop");
for (var j in o)
{
	document.writeln("<br /> j = ["+j+"]");
}

document.writeln("<br /><br /> Native Object Test ");

var p = new Object();

p.a = "a";
p.b = "b";
p.c = "c";



document.writeln("<br /><br /> test object contents =
["+p+"]");

document.writeln("<br /> c style for loop");
for (var i = 0; i < p.length; i++)
{
	document.writeln("<br /> i["+i+"] =
["+p[i]+"]");
}

document.writeln("<br /> for each loop");
for (var j in p)
{
	document.writeln("<br /> j = ["+j+"]");
}


document.writeln("<br /><br /> Prototype Object Test ");

var TestClass = Class.create();


TestClass.prototype {
   initialize: function(arg1,arg2,arg3)
   {

		this.a = arg1;
		this.b = arg2;
		this.c = arg3;
   },

   showMessage: function(msg)
   {
	  alert(msg);
   },


   forToString: function()
   {
	   document.writeln("<br /> c style for loop");
	   for (var i = 0; i < this.length; i++)
	   {
		   document.writeln("<br /> i["+i+"] =
["+this[i]+"]");
	   }

   },

   forEachToString: function()
   {
		document.writeln("<br /> for each loop");
		for (var j in this)
		{
			document.writeln("<br /> j = ["+j+"]");
		}
   }

};

var q = new TestClass("a","b","c");


document.writeln("<br /><br /> test object contents =
["+q+"]");
q.forToString();
q.forEachToString();

</script>

</body>
</html>
----------------------------------------------------------------------------
------


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Thomas Fuchs

2005-Sep-22 09:20 UTC

head link

[Rails-spinoffs] Prototype lib : for-each loops and DontEnum

This is fixed in the Prototype 1.4.0 pre-releases.

Thomas

Am 22.09.2005 um 14:45 schrieb SPENDLOVE, Matt, FM:
> All
>
> I realise that this isn''t strictly the correct place to discuss
the
> prototype lib but being as scriptaculous is dependent on it I  
> thought people
> might have some opinions.
>
> Easier to explain with the example below, copy into a html file and  
> ensure
> the path to prototype.js is correct. You''ll see the first example
> prints an
> extra element "extend" when iterating over the Array using a for-
> each loop..
>
> - Problem
>
> In a nutshell, because prototype adds an extra member variable to  
> the Object
> type (extend), it kinda breaks the for-each loop (for x in y) for all
> implicit js objects e.g. Array, presumable because they extend Object.
>
> Some code we use (perhaps incorrectly) assumes all members within a  
> custom
> object are things that it''s interested in. The addition of the  
> "extend"
> variable breaks things.
>
> We use Struts and it''s validator framework falls into this trap.

Rob Wills

2005-Sep-22 09:26 UTC

head link

[Rails-spinoffs] Prototype lib : for-each loops and DontEnum

On 22/09/05, SPENDLOVE, Matt, FM <Matt.SPENDLOVE@rbos.com>
wrote:>
> Easier to explain with the example below, copy into a html file and ensure
> the path to prototype.js is correct. You''ll see the first example
prints an
> extra element "extend" when iterating over the Array using a
for-each loop..
>
>
> Any thought / opinions or suggestions welcome.
>
Matt, what version of prototype are you using?

I had the exact same problem with the additional ''extend''
attribute,
until prototype was upgraded recently (in the last few months).

You might notice the section commented out at line 35 of prototype.js
version 1.4.0_pre2 ...

    /*
    Object.prototype.extend = function(object) {
      return Object.extend.apply(this, [this, object]);
    }
    */

Cheers,

Rob

SPENDLOVE, Matt, FM

2005-Sep-22 10:35 UTC

head link

[Rails-spinoffs] Prototype lib : for-each loops and DontEnum

Scriptaculous 1.0
Prototype 1.3.1

I guess that explains things. Not sure I have time to integrate / test a pre
release version though before my next app release :(

Thanks to all

Matt
> -----Original Message-----
> From: rails-spinoffs-bounces@lists.rubyonrails.org 
> [mailto:rails-spinoffs-bounces@lists.rubyonrails.org] On 
> Behalf Of Rob Wills
> Sent: 22 September 2005 14:04
> To: rails-spinoffs@lists.rubyonrails.org
> Subject: Re: [Rails-spinoffs] Prototype lib : for-each loops 
> and DontEnum
> 
> 
> On 22/09/05, SPENDLOVE, Matt, FM <Matt.SPENDLOVE@rbos.com> wrote:
> >
> > Easier to explain with the example below, copy into a html file and 
> > ensure the path to prototype.js is correct. You''ll see the
first
> > example prints an extra element "extend" when iterating 
> over the Array 
> > using a for-each loop..
> >
> 
> 
> >
> > Any thought / opinions or suggestions welcome.
> >
> 
> Matt, what version of prototype are you using?
> 
> I had the exact same problem with the additional ''extend''
> attribute, until prototype was upgraded recently (in the last 
> few months).
> 
> You might notice the section commented out at line 35 of 
> prototype.js version 1.4.0_pre2 ...
> 
>     /*
>     Object.prototype.extend = function(object) {
>       return Object.extend.apply(this, [this, object]);
>     }
>     */
> 
> Cheers,
> 
> Rob
> _______________________________________________
> Rails-spinoffs mailing list Rails-spinoffs@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails-spinoffs
> 

***********************************************************************************
The Royal Bank of Scotland plc. Registered in Scotland No 90312.      
Registered Office: 36 St Andrew Square, Edinburgh EH2 2YB.
Authorised and regulated by the Financial Services Authority     

This e-mail message is confidential and for use by the                      
addressee only. If the message is received by anyone other             
than the addressee, please return the message to the sender          
by replying to it and then delete the message from your                    
computer. Internet e-mails are not necessarily secure. The               
Royal Bank of Scotland plc does not accept responsibility for          
changes made to this message after it was sent.                              

Whilst all reasonable care has been taken to avoid the                   
transmission of viruses, it is the responsibility of the recipient to        
ensure that the onward transmission, opening or use of this             
message and any attachments will not adversely affect its               
systems or data.  No responsibility is accepted by The Royal           
Bank of Scotland plc in this regard and the recipient should carry   
out such virus and other checks as it considers appropriate.           

Visit our websites at:
http://www.rbs.co.uk/CBFM
http://www.rbsmarkets.com

********************************************************************************

Jon Tirsen

2005-Sep-22 18:15 UTC

head link

[Rails-spinoffs] Prototype lib : for-each loops and DontEnum

Just out of interest. What is it replaced with? (Yeah, I''m too lazy to
read the code...)

Cheers,
Jon

On 9/22/05, Thomas Fuchs <thomas@fesch.at> wrote:> This is fixed in the Prototype 1.4.0 pre-releases.
>
> Thomas
>
> Am 22.09.2005 um 14:45 schrieb SPENDLOVE, Matt, FM:
>
> > All
> >
> > I realise that this isn''t strictly the correct place to
discuss the
> > prototype lib but being as scriptaculous is dependent on it I
> > thought people
> > might have some opinions.
> >
> > Easier to explain with the example below, copy into a html file and
> > ensure
> > the path to prototype.js is correct. You''ll see the first
example
> > prints an
> > extra element "extend" when iterating over the Array using a
for-
> > each loop..
> >
> > - Problem
> >
> > In a nutshell, because prototype adds an extra member variable to
> > the Object
> > type (extend), it kinda breaks the for-each loop (for x in y) for all
> > implicit js objects e.g. Array, presumable because they extend Object.
> >
> > Some code we use (perhaps incorrectly) assumes all members within a
> > custom
> > object are things that it''s interested in. The addition of
the
> > "extend"
> > variable breaks things.
> >
> > We use Struts and it''s validator framework falls into this
trap.
>
> _______________________________________________
> Rails-spinoffs mailing list
> Rails-spinoffs@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails-spinoffs
>

Michael Schuerig

2005-Sep-22 21:24 UTC

head link

[Rails-spinoffs] Re: Prototype lib : for-each loops and DontEnum

On Thursday 22 September 2005 23:51, Jon Tirsen wrote:> Just out of interest. What is it replaced with? (Yeah, I''m too
lazy
> to read the code...)
  something.extend(somethingElse)

is replaced by

  Object.extend(something, somethingElse)

Michael

-- 
Michael Schuerig                         Those people who smile a lot
mailto:michael@schuerig.de                             Watch the eyes
http://www.schuerig.de/michael/    --Ani DiFranco, Outta Me, Onto You

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