What's wrong with Multidimensional Array?

--- Example 1
var myarray=[[],[]];
myarray[0][1]="NA"
print(myarray[0][1]); // output "NA"

--- Example 2
var myarray=[[],[]];
for (var x = 0; x < 5; x++) {
for (var y = 0; y < 5; y++) {
myarray[x][y]=0;
}
}

for (var x = 0; x < 5; x++)
print(myarray[x]); // output error myarray[x] is undefined !?!

What's wrong with example 2 ????

 

On Sun, 19 Feb 2012 12:52:00 +0100, Stefan Weiss <>
wrote:

>On 2012-02-19 12:37, Dominik wrote:
>> var myarray=[[],[]];
>
>myarray now has (empty) arrays at index 0 and 1.

--- Example 1.1
var myarray=[[],[]];
myarray[10][10]="NA"
print(myarray[10][10]); // output error myarray[10] is undefined

OMG What a mistake-a to make-a.
Thank you!

[snip]
>At the third iteration, you're trying to set myarray[2][0] = 0.
>myarray[2] is undefined, so you get an error.
>
>You could create the child arrays when you need them, instead of doing
>it in advance:

OK, I see it now.
But I'm curius, is it possible to create empty multidimensional array in
advance?

 

On Sun, 19 Feb 2012 14:16:08 +0100, Stefan Weiss <>
wrote:

>On 2012-02-19 13:32, Dominik wrote:
>> But I'm curius, is it possible to create empty multidimensional array in
>> advance?
>
>Well, strictly speaking there's no such thing as a multidimensional
>array in JS. There are only arrays of arrays. The two are often used in
>a similar way, but there are differences. One of them is that there's no
>way to initialize the child arrays with a simple statement*.

Thank you very much for your help.

 

Stefan Weiss wrote:

> In JS 1.7, you might use array comprehension to make the initialization
> more concise:
>
> var myarray = [[] for each (i in range(0, 4))];
> // assuming a suitable range() generator function
>
> Not very portable, though. If you need such arrays a lot, you may want
> to define a function to handle the initializations.

Given that, according to my current research, Array comprehension is *only*
supported in (Mozilla) JavaScript 1.7 and later, I do not think it deserves
the attribute "portable" at all.


PointedEars
--
var bugRiddenCrashPronePieceOfJunk = (
navigator.userAgent.indexOf('MSIE 5') != -1
&& navigator.userAgent.indexOf('Mac') != -1
) // Plone, register_function.js:16

 

Thomas 'PointedEars' Lahn wrote on 20 feb 2012 in comp.lang.javascript:

> Given that, according to my current research, Array comprehension is
> *only* supported in (Mozilla) JavaScript 1.7 and later, I do not think
> it deserves the attribute "portable" at all.

I fail to comprehend the meaning of such atributable comprehension, Thomas.

Could you divulge?

--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

 

In comp.lang.javascript message <irp1k7puv7pgmuhuuhnpovq6dolg7pubea@4ax.
com>, Sun, 19 Feb 2012 13:32:41, Dominik <> posted:

>
>OK, I see it now.
>But I'm curius, is it possible to create empty multidimensional array in
>advance?

One can assign a value to a variable which does not already exist.

For counting purposes, it would be useful to be able to increment a
variable which currently is value=undefined or is non-existent, with the
pre-increment value taken as either 0 or "", depending on the nature of
the increment. Possibly with X+++ and X ++= 7.

--
(c) John Stockton, nr London, UK. ?@merlyn.demon.co.uk Turnpike 6.05 WinXP.
Web <http://www.merlyn.demon.co.uk/> - FAQ-type topics, acronyms, and links.
Command-prompt MiniTrue is useful for viewing/searching/altering files. Free,
DOS/Win/UNIX now 2.0.6; see <URL:http://www.merlyn.demon.co.uk/pc-links.htm>.

 

Evertjan wrote:
> Thomas 'PointedEars' Lahn wrote on 20 feb 2012 in comp.lang.javascript:
>
>> Given that, according to my current research, Array comprehension is
>> *only* supported in (Mozilla) JavaScript 1.7 and later, I do not think
>> it deserves the attribute "portable" at all.
>
> I fail to comprehend the meaning of such atributable comprehension, Thomas.

<https://developer.mozilla.org/en/JavaScript/Guide/
Predefined_Core_Objects#Array_comprehensions>

-- Scott