Rails spinoffs - Jan 2007 - Bug with IE 6 (maybe 7, but dn't know)

Hello,

I''ve noticed that when you put a '','' at the end of
the last effect, IE
doesn''t work.

EX:
new Effect.Parallel(
 [
  new Effect.SlideDown(id,{duration:0.1}),
  new Effect.Opacity(id, {duration: 0.8, from: 0.0, to:1.0})
  ],
{duration: 1.0});

works perfectly, but

new Effect.Parallel(
 [
  new Effect.SlideDown(id,{duration:0.1}),
  new Effect.Opacity(id, {duration: 0.8, from: 0.0, to:1.0}),
  ],
{duration: 1.0});

doesn''t work on IE 6.

Oximore


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oximore-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
> Hello,
> 
> I''ve noticed that when you put a '','' at the end
of the last effect, IE
> doesn''t work.
It doesn''t work because it''s not really correct. Firefox
allows it which is
frankly a pain because you won''t catch the mistake unless you fire up
IE. I
admit that it''s a pain since other languages allow the extra comma
(Perl) and
you just get used to it.

-- 
Michael Peters
Developer
Plus Three, LP


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Michael Peters wrote:
> oximore-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
> > Hello,
> >
> > I''ve noticed that when you put a '','' at the
end of the last effect, IE
> > doesn''t work.
>
> It doesn''t work because it''s not really correct.
Not correct in what way?  It is legal ECMAScript syntax, however it is
interpreted incorrectly by IE which will add an extra element to the
array.  Therefore it may be "not correct" because Effect.Parallel
expects all elements in the array to have been assigned a value.
> Firefox allows it
Because Firefox follows the ECMAScript specification.  A trailing comma
in an Array literal should not create an extra element, however in IE
it will create an extra element with an unassigned value.

e.g.:

  var x = [,,,];
  alert(x.length); // shows 3 in Firefox, 4 in IE.

Firefox is correct, IE is wrong.
> which is
> frankly a pain because you won''t catch the mistake unless you fire
up IE.
Should Firefox use a non-compliant implementation and mimic IE''s bugs
just to save developers having to properly test their code?  You could
equally criticise the Effect class for not checking the values passed
to it.

> I
> admit that it''s a pain since other languages allow the extra comma
(Perl) and
> you just get used to it.
In this regard, ECMAScript is consistent with those "other languages"
-
it is IE''s flawed implementation of the specification that is the
difference.


-- 
Rob


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RobG wrote:
> Michael Peters wrote:
> > oximore-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
> > > Hello,
> > >
> > > I''ve noticed that when you put a '',''
at the end of the last effect, IE
> > > doesn''t work.
> >
> > It doesn''t work because it''s not really correct.
>
> Not correct in what way?  It is legal ECMAScript syntax, however it is
> interpreted incorrectly by IE which will add an extra element to the
> array.  Therefore it may be "not correct" because Effect.Parallel
> expects all elements in the array to have been assigned a value.
>
> > Firefox allows it
>
> Because Firefox follows the ECMAScript specification.  A trailing comma
> in an Array literal should not create an extra element, however in IE
> it will create an extra element with an unassigned value.
I''ll correct that.  IE increments the length, which is still incorrect
and within a for loop is equivalent to adding an element with value
''undefined''.  It should only increment the length for elisions
that
aren''t at the end of the element list.  e.g.

  var x = [ 1, ,2 ];   // length = 3;
  var x = [ 1, 2, ];   // length = 2;

IE will give a length of 3 for both.

As a bit of trivia, if a for..in loop is used, IE will get it right
since there is no element with index 3. :-)

-- 
Rob


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RobG wrote:
> 
> Michael Peters wrote:
>> oximore-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
>> > Hello,
>> >
>> > I''ve noticed that when you put a '','' at
the end of the last effect, IE
>> > doesn''t work.
>>
>> It doesn''t work because it''s not really correct.
> 
> Not correct in what way?  It is legal ECMAScript syntax, however it is
> interpreted incorrectly by IE which will add an extra element to the
> array.  Therefore it may be "not correct" because Effect.Parallel
> expects all elements in the array to have been assigned a value.
I''m sorry, I was a little confused. I thought you were talking about
trailing
commas in object literals.

  {
    stuff : ''foo'',
    more  : ''bar'',
  }

Am I mistaken, or are those allowed too?
> In this regard, ECMAScript is consistent with those "other
languages" -
> it is IE''s flawed implementation of the specification that is the
> difference.
I''m not trying to defend IE or say that other browsers should break
conformance
with the spec to accomodate MS. I was just mistaken. Sorry for the confusion.

-- 
Michael Peters
Developer
Plus Three, LP


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Michael Peters wrote:
> RobG wrote:
> >
> > Michael Peters wrote:
> >> oximore-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
> >> > Hello,
> >> >
> >> > I''ve noticed that when you put a
'','' at the end of the last effect, IE
> >> > doesn''t work.
> >>
> >> It doesn''t work because it''s not really correct.
> >
> > Not correct in what way?  It is legal ECMAScript syntax, however it is
> > interpreted incorrectly by IE which will add an extra element to the
> > array.  Therefore it may be "not correct" because
Effect.Parallel
> > expects all elements in the array to have been assigned a value.
>
> I''m sorry, I was a little confused. I thought you were talking
about trailing
> commas in object literals.
>
>   {
>     stuff : ''foo'',
>     more  : ''bar'',
>   }
>
> Am I mistaken, or are those allowed too?
Elisions (empty elements) aren''t allowed in object literals.  However,
I recall someone suggesting trailing commas in object literals be
tolerated and not throw an error as a proposal for JavaScript 2.0,
though I can''t find a reference for it right now.

The purpose of elisions in Array literals is to provide a short-cut
method of incrementing the length without creating empty elements,
e.g.:

  var x = [];
  x[2] = ''foo'';

should be identical to:

  var x = [ ,,''foo'' ];

That is, an array with length 3 and a single element at index 2.  IE
gets this example right, however there is a known bug in Gecko browsers
where elisions not at the end are created as elements and given the
value ''undefined''.  In Firefox the second example above
creates an
array with length 3, elements at index 0 and 1 with value
''undefined''
and at index 2 with value ''foo''.

With trailing elisions, the last one should have no effect: Gecko gets
that bit right, but IE doesn''t:

  var x = [ ''foo'',, ];

Should result in x having a length of 2 and a single element
''foo'' at
index 0.  Firefox gets the length right but has an ''undefined''
element
at index 1.  IE correctly doesn''t add elided elements but gets the
length wrong, setting it to 3.

>
> > In this regard, ECMAScript is consistent with those "other
languages" -
> > it is IE''s flawed implementation of the specification that is
the
> > difference.
>
> I''m not trying to defend IE or say that other browsers should
break conformance
> with the spec to accomodate MS. I was just mistaken. Sorry for the
confusion.
That''s OK.  Probably the most ECMAScript compliant browser is Opera.
When using a large and complex library (or a bunch of them in the case
of Prototype + Scriptaculous) across a variety of browsers it is often
difficult to tell whether code execution errors are the result of a
browser''s ECMAScript non-conformance or some quirk of the library.
Most browsers are very compliant, but there is the occasional gotcha.


-- 
Rob


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