jQuery.parseJSON disordered array

Question

Initial PHP ARRAY Storing attributes as values and respective id's on key

Array
(
[979] => Pict Model
[962] => Brand
[494] => Dimensions
[980] => Capacity
[981] => Power
[982] => List Price
[983] => Warrenty
[975] => USB Connection
[976] => Self Cleaning
[977] => Double Glass Door
[978] => Steam Function
[974] => Electricity Type
)

In my Code below, comparable_attr holds the json encoded array. After that, as i console.log(comparable_attr) This gives me a json of order as of php array.

Then, after i parseJSON and then console.log it gave me data in different order.

var comparable_attr = '<?php echo json_encode($_comparable_attributes); ?>';
   if(comparable_attr.length != 0){       //check for empty json
      console.log(comparable_attr);
          var obj = jQuery.parseJSON(comparable_attr);
                console.log(obj);
}

Problem : i want to achieve it in same order after i parseJSON.

The result obtained :

First Console.log(comparable_attr) gives:

{"979":"Pict Model","962":"Brand","494":"Dimensions","980":"Capacity","981":"Power","982":"List Price","983":"Warrenty","975":"USB Connection","976":"Self Cleaning","977":"Double Glass Door","978":"Steam Function","974":"Electricity Type"}

Second Console.log(obj) gives :

 Object { 494="Dimensions", 962="Brand", 974="Electricity Type", more...}

enter image description here

Edited :

What i have found is, it shorted according to my attribute id, which i need in the same order as it is in array.

Take a look at this question, it may help you out: http://stackoverflow.com/questions/12574068/jquery-getjson-sorts-my-data-by-id-automatically — Matheno, Oct 10 '14 at 07:41
yeah quite odd indeed, maybe related http://stackoverflow.com/questions/21216391/prevent-json-encode-associative-array-sorting — Kevin, Oct 10 '14 at 07:48
@Ghost it's not odd at all, it's a natural consequence of JS objects being explicitly _unordered_. — Alnitak, Oct 10 '14 at 08:04

Alnitak · Answer 1 · 2014-10-10T08:02:12.500

3

When you convert a PHP spare array into JSON and subsequently into a JS variable you will get a JS Object, not an array, and JS objects are explicitly an unordered set of key value pairs.

If you wish to preserve the order you will need to rearrange the data on the PHP side first, perhaps as:

Array(
    Array([979] => Pict Model),
    Array([962] => Brand),
    ...
)

Note however that if you do this you will lose the ability to directly lookup the data by key, as the resulting JS object would look like:

[
  { "979": "Pict Model" },  // NB: all JS keys are strings
  { "962": "Brand" },
  ...
]

An alternative might be to send your existing array as is, but also send a second array that is just the ordered list of keys. The former can be used for key-based lookup, the latter to determine the correct order:

json_encode(array(
    'data' => $_comparable_attributes,
    'order' => array_keys($_comparable_attributes)
));

edited Oct 10 '14 at 08:02

answered Oct 10 '14 at 07:51

Alnitak

334,560
70
407
495

what about swapping key and values form my array as both are string to me ? i solved that way (as it didn't sorted the alphabet being on key) but is it right to do this way ? – Suman KC Oct 10 '14 at 08:25
@K.C. hard to say without knowing why the order matters. Swapping the keys and values will still give you an object that's not sorted. – Alnitak Oct 10 '14 at 08:29
But Swapping gave me the same order as of php Array. Yeah, actually ordering matters here, it's that kinda case. Anyways Thank you. – Suman KC Oct 10 '14 at 08:33
@K.C. you can't rely on that ordering being preserved - in other browsers it could well be different. – Alnitak Oct 10 '14 at 08:52

Aleksei Matiushkin · Answer 2 · 2014-10-10T08:14:06.807

0

Javascript’s json object order is inplementation dependant. You could try it in the console:

a = {2:'a', 1:'b'}
Object {1: "b", 2: "a"}

To solve your problem I would suggest you to prevent auto sorting by:

array_reduce(
  $a, 
  function($carry, $item) use(&$a) { 
    $carry[] = [key($a), $item]; next($a); return $carry; 
  }, 
  []
)

This will wrap your initial array into array containing [key, val] items.

Hope this helps.

edited Oct 10 '14 at 08:14

answered Oct 10 '14 at 07:57

Aleksei Matiushkin

119,336
10
100
160

No, JSON representation of objects are _not_ automatically sorted by key. It's implementation dependant. – Alnitak Oct 10 '14 at 07:57
Yes, my mistake. Updated an answer. – Aleksei Matiushkin Oct 10 '14 at 07:58
Also, your output will be `[[key1, val1], [key2, val2], ...]` - not the `[[key1 => X, val1 => Y], ...]` associative array you've shown. The latter is an array of objects, the former an array of arrays. – Alnitak Oct 10 '14 at 08:07
@Alnitak thatnks for explanation the difference between arrays and objects. – Aleksei Matiushkin Oct 10 '14 at 08:15
Also `array_map(function($k, $v) { return array($k, $v); }, array_keys($a), $a)` is simpler than using `array_reduce`. – Alnitak Oct 10 '14 at 08:24
`array_reduce` is flexible. My intention was not to give a ready-to-go solution, but to show a technique. – Aleksei Matiushkin Oct 10 '14 at 08:26

jQuery.parseJSON disordered array

2 Answers2