for in loop. reverse traverse

**Michael Winter** · Jul 23 '05, 03:47 PM

Re: for in loop. reverse traverse

On 9 Dec 2004 11:17:15 -0800, R. Rajesh Jeba Anbiah
<ng4rrjanbiah@r ediffmail.com> wrote:
[color=blue]
> Unfortunately, I couldn't find any way to traverse the object array in
> reverse order.[/color]

What's an object array?
[color=blue]
> I'd thought there must be a way to do it with for..in loop, but couldn't
> find anything yet.[/color]

The for..in statement doesn't return values in any particular order so
reversing is not possible.

[snip]

Mike

--
Michael Winter
Replace ".invalid" with ".uk" to reply by e-mail.

**Joakim Braun** · Jul 23 '05, 03:47 PM

Re: for in loop. reverse traverse

"R. Rajesh Jeba Anbiah" <ng4rrjanbiah@r ediffmail.com> skrev i meddelandet
news:1102619835 .408631.286170@ z14g2000cwz.goo glegroups.com.. .[color=blue]
> Unfortunately, I couldn't find any way to traverse the object array in
> reverse order. I'd thought there must be a way to do it with for..in
> loop, but couldn't find anything yet. Could someone please help me?
> TIA.
>
> --
> <?php echo 'Just another PHP saint'; ?>
> Email: rrjanbiah-at-Y!com Blog: http://rajeshanbiah.blogspot.com/[/color]

A probably meaningless hack would be to do a for...in with the object and
save the property names in an array. Then traverse that array backwards and
access the named properties of the first object.

Joakim Braun

**Grant Wagner** · Jul 23 '05, 04:01 PM

Re: for in loop. reverse traverse

comp.lang.javas cript FAQ - http://jibbering.com/faq
"Joakim Braun" <joakim.braun@j fbraun.removeth is.com> wrote in message
news:e74ud.3043 $Of5.2157@nntps erver.swip.net. ..[color=blue]
> "R. Rajesh Jeba Anbiah" <ng4rrjanbiah@r ediffmail.com> skrev i[/color]
meddelandet[color=blue]
> news:1102619835 .408631.286170@ z14g2000cwz.goo glegroups.com.. .[color=green]
> > Unfortunately, I couldn't find any way to traverse the object array[/color][/color]
in[color=blue][color=green]
> > reverse order. I'd thought there must be a way to do it with for..in
> > loop, but couldn't find anything yet. Could someone please help me?
> > TIA.
> >
> > --
> > <?php echo 'Just another PHP saint'; ?>
> > Email: rrjanbiah-at-Y!com Blog: http://rajeshanbiah.blogspot.com/[/color]
>
> A probably meaningless hack would be to do a for...in with the object[/color]
and[color=blue]
> save the property names in an array. Then traverse that array[/color]
backwards and[color=blue]
> access the named properties of the first object.[/color]

But the values retrieved with for...in aren't guaranteed to be in any
particular order in the first place, so "reverse order" has no meaning,
since you can't be sure what the "forward order" will be.

If you want to store key/value pairs and be guaranteed of their order,
you will need to store both the key/value pair and the order they are
added in:

function MyOrderedMap() {
var keys = [];
var values = [];

this.add = function(key, value) {
// test to make sure 'key' isn't in 'keys'
var ii = keys.length;
while (ii-- > 0) {
if (key == keys[ii]) {
return false;
}
}
keys.push(key);
values.push(val ues);
return true;
}
this.getKeysInR everseOrder = function() {
return keys.reverse();
// or return keys.reverse(). join(',');
// or whatever you want
}
}

You probably want methods for getting a value when passed a key:

this.getValue = function(key) {
var ii = keys.length;
while (ii-- > 0) {
if (key == keys[ii]) {
return values[ii];
}
}
return null;
}

and other methods as well to clear the list, etc.

I threw this together in a hurry, there may be syntax errors.

--
Grant Wagner <gwagner@agrico reunited.com>

for in loop. reverse traverse

for in loop. reverse traverse

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