inspecting javascript arrays

Question

In PHP I can loop through an array with a foreach as loop to examine the contents of the array

$array = array(...);
foreach($array as $K=>$V){
    echo $K." = ".$V;
}

I would like to do something similar to inspect my javascript array

var array = new Array();
foreach(array ...){
    window.alert(...);
}

how can I do this?

EDIT

I should have noted that I need both the keyname AND the value

EDIT AGAIN

var $_SESSION = new Array();
$_SESSION['pin'] = "asdf";
$_SESSION['something'] = "1234";
$_SESSION['something_else'] = "123";

here's an example of my array^

Just use a "normal" `for` loop: `for(var i = 0; i < array.length; i++){ alert(array[i]); }` — gen_Eric, Mar 18 '14 at 20:54
JavaScript doesn't have "associative arrays". What *exactly* is it that you have? — gen_Eric, Mar 18 '14 at 20:59
@RocketHazmat I posted an example of what I mean by "Associative array" This is pretty much what I'm working with. I need to window.alert each index with both the keyname and the value. — I wrestled a bear once., Mar 18 '14 at 21:04
That's what you have in PHP! I was asking what you have in *JavaScript*. "Associative arrays" *don't exist* in JavaScript (the term is not used in that language). I'm assuming you have an *object* (which is *not* an array). Objects and Arrays are handled differently in JavaScript. — gen_Eric, Mar 18 '14 at 21:06
@RocketHazmat no I know $_SESSION is a PHP thing but I'm using as the name of my JS array, as it holds the same data. — I wrestled a bear once., Mar 18 '14 at 21:07
How are you storing that data in JavaScript? Can you show us that? I'm fairly certain that the "array" you have is not what you think it is. — gen_Eric, Mar 18 '14 at 21:08
Indeed it is (I didn't notice the 1st time), though what you have created is *not* an "associative array". You have created an array (with 0 elements) in it, then you added 3 properties to it. This is not the correct way to create the data structure you want. You want to create an object. `var $_SESSION = {}; $_SESSION['pin'] = "asdf";` (or `var $_SESSION = {pin: 'asdf'};`). — gen_Eric, Mar 18 '14 at 21:11
it was just an example, I'm working with a javascript "class".. putting "class" in quotes since we're being technical.. — I wrestled a bear once., Mar 18 '14 at 21:14

deweyredman · Accepted Answer · 2014-03-18T21:00:42.073

2

basically you would do something like this:

for(var i in array) {
     if(array.hasOwnProperty(i)){
          alert(array[i]);
     }
}

EDITED: to check for presence of key in object.

edited Mar 18 '14 at 21:00

answered Mar 18 '14 at 20:54

deweyredman

1,440
1
9
12

I wouldn't use `for..in` for arrays. – gen_Eric Mar 18 '14 at 20:55
Thanks, it's an associative array though. How can I make this work with an associative array? – I wrestled a bear once. Mar 18 '14 at 20:55
@Adelphia: JavaScript doesn't have "associative arrays". – gen_Eric Mar 18 '14 at 20:56
ok, well how do I get the keyname then? this only shows how to display the value of each index. @RocketHazmat – I wrestled a bear once. Mar 18 '14 at 20:59
sure, if it's an associative array, you coudl do a check like this:if (if array.hasOwnProperty('key') ) { //do this } – deweyredman Mar 18 '14 at 20:59
1

@Adelphia: The key is `i`. Can you show us how you're adding elements to `array`. I don't think you have what you think you have. – gen_Eric Mar 18 '14 at 20:59
@RocketHazmat To be more precise, JavaScript doesn't have anything but associative arrays. – sabof Mar 18 '14 at 21:00
1

@sabof: I understand what you mean, but don't say that. It's just confusing, and incorrect. JavaScript has "objects" (which are *not* "associative arrays"). – gen_Eric Mar 18 '14 at 21:01

score 1 · Answer 2 · answered Mar 18 '14 at 20:58

function logArrayElements(element, index, array) {
    console.log("a[" + index + "] = " + element);
}
[2, 5, 9].forEach(logArrayElements);
// logs:
// a[0] = 2
// a[1] = 5
// a[2] = 9

(taken from here)

Note that this isn't compatible with IE8 or lower. There simply was no foreach control in older javascript versions.

score 0 · Answer 3 · edited May 23 '17 at 11:57

0

for (var a = 0, b = array.length; a < b; a++) {
    alert(array[a]);
}

Defining b = array.length speeds up the loop as a < array.length would re-check the length of the array on each iteration.

Here's why you shouldn't use for ... in.

edited May 23 '17 at 11:57

Community

1
1

answered Mar 18 '14 at 21:01

Adrian J. Moreno

14,350
1
37
44

inspecting javascript arrays

3 Answers3