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: stackoverflow.com/questions/12574068/… — Matheno
– Matheno, Commented Oct 10, 2014 at 7:41
yeah quite odd indeed, maybe related stackoverflow.com/questions/21216391/… — Kevin
– Kevin, Commented Oct 10, 2014 at 7:48
@Ghost it's not odd at all, it's a natural consequence of JS objects being explicitly unordered. — Alnitak
– Alnitak, Commented Oct 10, 2014 at 8:04

Alnitak · Accepted Answer · 2014-10-10 08:02:12Z

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, 2014 at 8:02

answered Oct 10, 2014 at 7:51

Alnitak

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4 Comments

Suman KC Over a year ago

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 ?

Alnitak Over a year ago

@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.

Suman KC Over a year ago

But Swapping gave me the same order as of php Array. Yeah, actually ordering matters here, it's that kinda case. Anyways Thank you.

Alnitak Over a year ago

@K.C. you can't rely on that ordering being preserved - in other browsers it could well be different.

Aleksei Matiushkin · Accepted Answer · 2014-10-10 08:14:06Z

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, 2014 at 8:14

answered Oct 10, 2014 at 7:57

Aleksei Matiushkin

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6 Comments

Alnitak Over a year ago

No, JSON representation of objects are not automatically sorted by key. It's implementation dependant.

Aleksei Matiushkin Over a year ago

Yes, my mistake. Updated an answer.

Alnitak Over a year ago

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.

Aleksei Matiushkin Over a year ago

@Alnitak thatnks for explanation the difference between arrays and objects.

Alnitak Over a year ago

Also array_map(function($k, $v) { return array($k, $v); }, array_keys($a), $a) is simpler than using array_reduce.

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