address array by variable variable

**Vincent van Beveren** · Jul 23 '05, 12:17 PM

Re: address array by variable variable

> Suppose.....[color=blue]
>
>
> arr = Array("only","a ","test");
> ArrayVar = "arr";
> alert(ArrayVar[0]);
>
> This the simplyfied version of my problem.. (alerting 'undefined' instead of
> 'only'...)[/color]

I think this is what you are looking for:

eval(ArrayVar+"[0]");

But you can also do the following

arr1 = Array("only", "a", "test");
arr2 = Array("only", "another", "test");

curArray = arr1;
alert(curArray[1]); // displays 'a';

curArray = arr2;
alert(curArray[1]); // displays 'another';

Which feels better.

Good luck,
Vincent

**Ivo** · Jul 23 '05, 12:17 PM

Re: address array by variable variable

"mps@webmind.nl " wrote[color=blue]
>
> arr = Array("only","a ","test");
> ArrayVar = "arr";
> alert(ArrayVar[0]);
>
> This the simplyfied version of my problem.. (alerting 'undefined' instead[/color]
of[color=blue]
> 'only'...)
>
> Now I use the most ugly workaround:
> if(ArrayVar == "arr") { alert(arr[0]); }
>
> But there has to be a much better solution?????[/color]

Not sure what you are trying to do. ArrayVar is a now string variable. If
you remove the quotes from your second line above, so it becomes

ArrayVar = arr;

then ArrayVar will be an array too, and ArrayVar[0] will be "only".
HTH
Ivo

**lallous** · Jul 23 '05, 12:17 PM

Re: address array by variable variable

Hello

"mps@webmind.nl "
<*DONT*[mps]_YOU#DARE(SEND) SPAM@@[webmind]--TOME.[.nl]%%^.orgtext> wrote in
message news:40fbc710$0 $78439$e4fe514c @dreader5.news. xs4all.nl...[color=blue]
> Suppose.....
>
>
> arr = Array("only","a ","test");
> ArrayVar = "arr";
> alert(ArrayVar[0]);
>
> This the simplyfied version of my problem.. (alerting 'undefined' instead[/color]
of[color=blue]
> 'only'...)
>
> Now I use the most ugly workaround:
> if(ArrayVar == "arr") { alert(arr[0]); }
>
> But there has to be a much better solution?????
>[/color]

Yes, you can use eval() as other indicated or you can use something like:

<script>
var x;

array1 = new Array("hello", "world");

x = "array1";

alert(window[x][0]); // <-- hello

</script>

The variables are stored under the window object. You can also do something
like: window["array1"][N] ...

--
Elias

**Quarco** · Jul 23 '05, 12:17 PM

Re: address array by variable variable

That is my problem: trying to retrieve an array item with a string
variable-name..
You see, the more elaborate version of my problem is

an array with positions:
positions =
("liggend","sta and","staand"," liggend","staan d","staand","li ggend");

an array
liggend[0] = array("value1a" ,"value2a","val ue3a","value4a" ,"value5a");
liggend[1] = array("value1b" ,"value2b","val ue3b","value4b" ,"value5b");
....
staand[0] = array("value1c" ,"value2c","val ue3c","value4c" ,"value5c");
...etc..

Now:
getValue(3) { //For example...
ArrayVar = positions[3]; // in this example ArrayVar = liggend
for(anItem in ArrayVar) {
...... /// walk through the 'liggend-array'..
}
}

I believe the eval function from Vincent does the trick...

Marco

"Ivo" <no@thank.you > schreef in bericht
news:40fbcac4$0 $62721$ee9da40f @news.wanadoo.n l...[color=blue]
> "mps@webmind.nl " wrote[color=green]
> >
> > arr = Array("only","a ","test");
> > ArrayVar = "arr";
> > alert(ArrayVar[0]);
> >
> > This the simplyfied version of my problem.. (alerting 'undefined'[/color][/color]
instead[color=blue]
> of[color=green]
> > 'only'...)
> >
> > Now I use the most ugly workaround:
> > if(ArrayVar == "arr") { alert(arr[0]); }
> >
> > But there has to be a much better solution?????[/color]
>
> Not sure what you are trying to do. ArrayVar is a now string variable. If
> you remove the quotes from your second line above, so it becomes
>
> ArrayVar = arr;
>
> then ArrayVar will be an array too, and ArrayVar[0] will be "only".
> HTH
> Ivo
>
>[/color]

**Quarco** · Jul 23 '05, 12:17 PM

Re: address array by variable variable

Hey,

Great..
It works!!

Thanx all for your time!!

Regards,
Marco

"lallous" <lallous@lgwm.o rg> schreef in bericht
news:2m22a7Fi7a iuU1@uni-berlin.de...[color=blue]
> Hello
>
> "mps@webmind.nl "
> <*DONT*[mps]_YOU#DARE(SEND) SPAM@@[webmind]--TOME.[.nl]%%^.orgtext> wrote[/color]
in[color=blue]
> message news:40fbc710$0 $78439$e4fe514c @dreader5.news. xs4all.nl...[color=green]
> > Suppose.....
> >
> >
> > arr = Array("only","a ","test");
> > ArrayVar = "arr";
> > alert(ArrayVar[0]);
> >
> > This the simplyfied version of my problem.. (alerting 'undefined'[/color][/color]
instead[color=blue]
> of[color=green]
> > 'only'...)
> >
> > Now I use the most ugly workaround:
> > if(ArrayVar == "arr") { alert(arr[0]); }
> >
> > But there has to be a much better solution?????
> >[/color]
>
> Yes, you can use eval() as other indicated or you can use something like:
>
> <script>
> var x;
>
> array1 = new Array("hello", "world");
>
> x = "array1";
>
> alert(window[x][0]); // <-- hello
>
> </script>
>
>
> The variables are stored under the window object. You can also do[/color]
something[color=blue]
> like: window["array1"][N] ...
>
> --
> Elias
>
>[/color]

**Lee** · Jul 23 '05, 12:17 PM

Re: address array by variable variable

SEND said:[color=blue]
>
>Suppose.....
>
>
>arr = Array("only","a ","test");
>ArrayVar = "arr";
>alert(ArrayV ar[0]);
>
>This the simplyfied version of my problem.. (alerting 'undefined' instead of
>'only'...)
>
>Now I use the most ugly workaround:
>if(ArrayVar == "arr") { alert(arr[0]); }
>
>But there has to be a much better solution?????[/color]

It depends on what you're really trying to do. If you just need
a way to use a variable name for an array, then you can use a
reference, instead of a string holding the name:

var myRef=arr;
alert(myRef[0]);

If you really need to use the string name, then there is probably
a better design that you could use, but one way to do it is:

var arrayGroup = { arr: [ "only", "a", "test" ],
brr: [ "a", "different" , "array" ],
crr: [ "one", "more", "example" ]
};
alert(arrayGrou p["arr"][0]);

You could also use eval(), but that is inefficient and difficult
to debug.

**Lasse Reichstein Nielsen** · Jul 23 '05, 12:18 PM

Re: address array by variable variable

"Quarco" <*DONT*[mps]_YOU#DARE(SEND) SPAM@@[webmind]--TOME.[.nl]%%^.orgtext> writes:
[color=blue]
> That is my problem: trying to retrieve an array item with a string
> variable-name..[/color]

In my experience, you are using a wrong approach to solve the real problem.
I have never seen a case where it was necessary to address a variable
using a string containing its name. Whatever you are trying to do, I'll
almost guarantee I can find a better way to do it :)
[color=blue]
> an array with positions:
> positions =
> ("liggend","sta and","staand"," liggend","staan d","staand","li ggend");
>
> an array
> liggend[0] = array("value1a" ,"value2a","val ue3a","value4a" ,"value5a");
> liggend[1] = array("value1b" ,"value2b","val ue3b","value4b" ,"value5b");
> ...
> staand[0] = array("value1c" ,"value2c","val ue3c","value4c" ,"value5c");
> ..etc..[/color]

Instead, do:

var c = new Object(); // container object
c.liggend = new Array();
c.staand = new Array();
and then
c.liggend[0] = ...
c.liggend[1] = ...
c.liggend[2] = ...
...
c.staand[0] = ...
c.staand[1] = ...
[color=blue]
> getValue(3) { //For example...
> ArrayVar = positions[3]; // in this example ArrayVar = liggend
> for(anItem in ArrayVar) {[/color]

function getValue(i) {
var arrayVar = positions[i];
var arr = c[arrayVar]
for(index in arr) {
var item = arr[index];
// ...
}
...
[color=blue]
> I believe the eval function from Vincent does the trick...[/color]

"eval" is almost never the best solution. It is inefficient and
errorprone, and should be left for the few cases where it can't be
avoided.
[color=blue]
> "Ivo" <no@thank.you > schreef in bericht
> news:40fbcac4$0 $62721$ee9da40f @news.wanadoo.n l...[/color]

Please don't top post.

Regards
/L
--
Lasse Reichstein Nielsen - lrn@hotpop.com
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleD OM.html>
'Faith without judgement merely degrades the spirit divine.'

**Lasse Reichstein Nielsen** · Jul 23 '05, 12:18 PM

Re: address array by variable variable

"Quarco" <*DONT*[mps]_YOU#DARE(SEND) SPAM@@[webmind]--TOME.[.nl]%%^.orgtext> writes:

On second thought, this solution is even prettier:

---
var liggend = [
["value1a","valu e2a","value3a", "value4a","valu e5a"],
["value1b","valu e2b","value3b", "value4b","valu e5b"],
...
];
var staand = [
["value1c","valu e2c","value3c", "value4c","valu e5c"],
...
];

var positions = [liggend, staand, staand, liggend, staand, staand, liggend];

function getValue(i) {
var arr = positions[i];
for (var index in arr) {
var item = arr[index];
...
}
...
---

Good luck.
/L
--
Lasse Reichstein Nielsen - lrn@hotpop.com
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleD OM.html>
'Faith without judgement merely degrades the spirit divine.'

**Quarco** · Jul 23 '05, 12:18 PM

Re: address array by variable variable

Hmmm ..

Think this is the 'ultimate' solution Lasse... :-)

Thanx a lot!

Marco

"Lasse Reichstein Nielsen" <lrn@hotpop.com > schreef in bericht
news:658ju9lc.f sf@hotpop.com.. .[color=blue]
> "Quarco"[/color]
<*DONT*[mps]_YOU#DARE(SEND) SPAM@@[webmind]--TOME.[.nl]%%^.orgtext> writes:[color=blue]
>
> On second thought, this solution is even prettier:
>
> ---
> var liggend = [
> ["value1a","valu e2a","value3a", "value4a","valu e5a"],
> ["value1b","valu e2b","value3b", "value4b","valu e5b"],
> ...
> ];
> var staand = [
> ["value1c","valu e2c","value3c", "value4c","valu e5c"],
> ...
> ];
>
> var positions = [liggend, staand, staand, liggend, staand, staand,[/color]
liggend];[color=blue]
>
> function getValue(i) {
> var arr = positions[i];
> for (var index in arr) {
> var item = arr[index];
> ...
> }
> ...
> ---
>
> Good luck.
> /L
> --
> Lasse Reichstein Nielsen - lrn@hotpop.com
> DHTML Death Colors:[/color]
<URL:http://www.infimum.dk/HTML/rasterTriangleD OM.html>[color=blue]
> 'Faith without judgement merely degrades the spirit divine.'[/color]

address array by variable variable

address array by variable variable

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