array.["property"]

[josh]

Hi all,
what does it meaning that strange sintax (look at the object :) ?

if I have i.e. array.length I can use array.["length"] and is it
IE/Firefox compatible??

[adamraney]

Try it without the dot:

array['length'] is equivilant to array.length.

On Nov 21, 8:09 am, "josh" <xdevel2...@yah oo.comwrote:

Hi all,
what does it meaning that strange sintax (look at the object :) ?

if I have i.e. array.length I can use array.["length"] and is it
IE/Firefox compatible??

[Martijn Saly]

josh wrote:

Hi all,
what does it meaning that strange sintax (look at the object :) ?

if I have i.e. array.length I can use array.["length"] and is it
IE/Firefox compatible??

array["length"] is equivalent to array.length

In javascript, an object is the same as an associative array, which
makes the formal difference between arrays and objects blurry.

This is defined by the ECMA-262 standard, and is thus compatible with
all browsers and all javascript engines.

array.["length"] (mind the dot) is a syntax error. Some javascript
parsers *may* tolerate it but you *shouldn't* count on it.
--
Martijn Saly

[Lee]

josh said:

>
Hi all,
what does it meaning that strange sintax (look at the object :) ?

You seem to mean "look at the subject", and that's a nuisance with
some newsreaders. Don't ask people to read the subject while
they're reading the message.

>if I have i.e. array.length I can use array.["length"] and is it
IE/Firefox compatible??

No, you can't use that syntax in any browser, but you should be
able to use: array["length"] in any. There's no "dot".

You can use this notation to access attributes of any Object.
--

[josh]

Martijn Saly ha scritto:

In javascript, an object is the same as an associative array, which
makes the formal difference between arrays and objects blurry.

please explain better what it mean 'makes the formal difference between
arrays and objects blurry'

[Martijn Saly]

josh wrote:

Martijn Saly ha scritto:

>In javascript, an object is the same as an associative array, which
makes the formal difference between arrays and objects blurry.

please explain better what it mean 'makes the formal difference between
arrays and objects blurry'

I mean to say that an object is so similar to an array that it becomes
difficult to explain what an object is compared to an array.

Consider an *object* with a length property. It can be accessed in two ways:

obj.length
obj["length"]

An *array* shows the same behavior, its second element can be accessed
in two ways:

array[1]
array.1
I would say the only difference is the way they are constructed. An
objects goes like one of these:

var obj = {foo: bar};
var obj = new Something(args) ;

but an array constructor producing an array with 2 elements goes like this:

var array = [foo, bar];
So you see, I can't really tell the functional difference between an
object and an array, other then the methods that come with an array.

--
Martijn Saly

[Randy Webb]

Martijn Saly said the following on 11/21/2006 9:29 AM:

josh wrote:

>Hi all,
what does it meaning that strange sintax (look at the object :) ?

if I have i.e. array.length I can use array.["length"] and is it
IE/Firefox compatible??

array["length"] is equivalent to array.length

In javascript, an object is the same as an associative array, which
makes the formal difference between arrays and objects blurry.

NO! An Object in JS is *NOT* an associative array. JS doesn't have an
associative array - period.

--
Randy
Chance Favors The Prepared Mind
comp.lang.javas cript FAQ - http://jibbering.com/faq
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/

[Randy Webb]

Martijn Saly said the following on 11/21/2006 10:21 AM:

josh wrote:

>Martijn Saly ha scritto:

>>In javascript, an object is the same as an associative array, which
makes the formal difference between arrays and objects blurry.

please explain better what it mean 'makes the formal difference between
arrays and objects blurry'

I mean to say that an object is so similar to an array that it becomes
difficult to explain what an object is compared to an array.

Consider an *object* with a length property. It can be accessed in two
ways:

obj.length
obj["length"]

An *array* shows the same behavior, its second element can be accessed
in two ways:

array[1]
array.1
I would say the only difference is the way they are constructed. An
objects goes like one of these:

var obj = {foo: bar};
var obj = new Something(args) ;

but an array constructor producing an array with 2 elements goes like this:

var array = [foo, bar];

Or like this:

var myArray = new Array(foo,bar)

or like this:

var myArray = new Array();
myArray[0] = foo
myArray[1] = bar

So you see, I can't really tell the functional difference between an
object and an array, other then the methods that come with an array.

You can give an Object a property called "length" and it can be unique
and meaningful to the programmer. That can not be said for an Array as
it has a very specific use of the length property.

--
Randy
Chance Favors The Prepared Mind
comp.lang.javas cript FAQ - http://jibbering.com/faq
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/

[RobG]

josh wrote:

Martijn Saly ha scritto:

In javascript, an object is the same as an associative array, which
makes the formal difference between arrays and objects blurry.

please explain better what it mean 'makes the formal difference between
arrays and objects blurry'

A javascript Array *is* an Object, it has a special length property (it
is self-adjusting and has a value that is always one higher than the
highest index) and a bunch of extra methods - push(), split(), pop(),
etc.

Javascript does not have "associativ e arrays". Its native Object uses
name:value pairs that make it similar to an associative array that can
be found in other languages, but it lacks features that might be
expected of an associative array.
--
Rob

[Matt Kruse]

Randy Webb wrote:

NO! An Object in JS is *NOT* an associative array. JS doesn't have an
associative array - period.

Must this continue to be said?

The fact is, there is no one definition for what an "associativ e array" is.
So how can you say that a js Object is not one?

Depending on how you choose to define an "associativ e array", an Object in
javascript can most certainly be described as one.

IMO, most programmers looking for an "associativ e array" in javascript are
in fact looking for what an Object offers. Despite its quirks and special
cases, I've never met or heard of a single person who was looking for an
associative array who was not satisfied using an Object.

I propose:

<FAQENTRY>

Q: How do I implement an Associative Array in Javascript?

A: The term Associative Array is vague, having different meanings in
different languages, so it's impossible to know what behavior is expected of
an Associative Array implementation. However, Javascript's Object() can
behave as a key/value storage object, which is the minimum that most people
expect from an Associative Array implementation.

A simple example:

var assocArray = {};
assocArray["key"] = "value";
alert(assocArra y["key"]);
for (var key in assocArray) {
alert(key + " = " + assocArray[key]);
}

Using a Javascript Object() as an Associative Array comes with the following
limitations:
1. Keys must be strings, not arbitrary objects.
2. Some keys are invalid, because Javascript's Object has built-in
properties that cannot be over-written.
3. Some keys will exist by default because of Object's built-in properties.
These will not be enumerated in for..in loops but can be directly accessed.
4. No method or property exists by default to retrieve the size - or number
of keys - currently stored.

</FAQENTRY>

--
Matt Kruse
http://www.JavascriptToolbox.com
http://www.AjaxToolbox.com