How do I get keys from an associative array?
 

Hi,

Given an associative array, how do I get an array of the keys of that
associative array?

Thanks, - Dave

Re: How do I get keys from an associative array?
 

laredotornado wrote:
> Hi,
>
> Given an associative array, how do I get an array of the keys of that
> associative array?
>

There's no such thing as an associative array in JS.

If you mean an Object object, use a for-in loop to populate an array.
And make sure you filter the loop with either hasOwnProperty or a
similar wrapper (Google "for-in intrigue").

Re: How do I get keys from an associative array?
 

laredotornado wrote:

> Given an associative array, how do I get an array of the keys of that
> associative array?

Mu.

<http://jibbering.com/faq/#posting>


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Re: How do I get keys from an associative array?
 

laredotornado <laredotornado@zipmail.com> writes:

> Given an associative array, how do I get an array of the keys of that
> associative array?

If arr is your associative array (i.e., an object)
In ECMAScript 5:
var keys = Object.keys(object)
In ECMAScript 3:
var keys = [];
for (var key in arr) { keys.push(key); }

/L
--
Lasse Reichstein Holst Nielsen
'Javascript frameworks is a disruptive technology'

Re: How do I get keys from an associative array?
 

Lasse Reichstein Nielsen wrote:

> laredotornado <laredotornado@zipmail.com> writes:
>> Given an associative array, how do I get an array of the keys of that
>> associative array?
>
> If arr is your associative array (i.e., an object)
> In ECMAScript 5:
> var keys = Object.keys(object)
> In ECMAScript 3:
> var keys = [];
> for (var key in arr) { keys.push(key); }

Where certain conditions must apply for the two approaches to be
equivalent, of course.

Let `o' be a reference to an object, JavaScript 1.7+ allows another
variant, Array comprehension:

var properties = [p for (p in o)];

BTW, for the property values you can use

var values = [v for each (v in o)];

there, as a combination of the ECMA-262-3 extension (v1.7+) and the
ECMA-357 implementation (v1.6+). Tested in Firefox/Iceweasel 3.5.8.


PointedEars
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realism: HTML 4.01 Strict
evangelism: XHTML 1.0 Strict
madness: XHTML 1.1 as application/xhtml+xml
-- Bjoern Hoehrmann

Re: How do I get keys from an associative array?
 

In comp.lang.javascript message <tytbxo8f.fsf@gmail.com>, Sun, 21 Feb
2010 04:27:12, Lasse Reichstein Nielsen <lrn.unread@gmail.com> posted:
>laredotornado <laredotornado@zipmail.com> writes:
>
>> Given an associative array, how do I get an array of the keys of that
>> associative array?
>
>If arr is your associative array (i.e., an object)
>In ECMAScript 5:
> var keys = Object.keys(object)
>In ECMAScript 3:
> var keys = [];
> for (var key in arr) { keys.push(key); }

The second entry should I suppose be headed "In ECMAScript 3 & 5"; and
will then be the way to code it (for the open Web) until all browsers in
use are sufficiently ES 5 compliant.

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