CODEWITHSUNDEEP
javascript
Torge
Torge

Reputation: 2284

How to sort an integer keyed object by value in javascript

I have a map of id => value that I want to sort by value. But no matter what I do, it always gets sorted by id.

Basically I have a sorted map on server side that I send to javascript via json.

{"3":"Apple","2":"Banana","1":"Orange"}

After de-serialization I get 

{
    1:"Orange",
    2:"Banana",
    3:"Apple"
}

And no matter what I try, it seems to stay in this order. Is it possible in javascript to force a non ascending sort order with interger keys?

var json = '{"3":"Apple", "2":"Banana", "1":"Orange"}';

var data = $.parseJSON(json);

for (var ix in data) {
  console.log(ix + ": " + data[ix]);
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

Upvotes: 1

Views: 1457

Answers (1)

briosheje
briosheje

Reputation: 7446

You should not rely on objects key order for these reasons.

I personally would recommend you to either use a Map, or to build an Array instead.

Below is an example to build an array from your source: for simplicity, I've added a key property to make the sorting easier.

Note: I'm using Array.from to build the array, which is taking the length from the parsed object keys length, and using the callback to init the object inline.

var json = '{"3":"Apple", "2":"Banana", "1":"Orange"}';

// Parse the json string.
const parsed = JSON.parse(json);
// Acquire the keys length
const length = Object.keys(parsed).length;
// Build an array of objects ordered in the same way it came.
const result = Array.from({length}, (_, i) => ({key: length - i, [length - i]: parsed[length - i]}));
// Log a copy of the result.
console.log(JSON.parse(JSON.stringify(result)));
// Sort ascending:
result.sort((a,b) => a.key - b.key);
// Log a copy of the sorted result.
console.log(JSON.parse(JSON.stringify(result)));
// Sort descending:
result.sort((a,b) => b.key - a.key);
// log the sorted array
console.log(result);

If you really want to rely on key orders, you can (of course), but using an array is slightly cleverer and gives no chance to have something which is not ordered as expected, unless (of course) the sorting algorithm is wrong or fails for some reason (like if key is undefined or null or not numeric in the above case).

As a final note, I'm aware that the question is about sorting an object, but because of the above reasons, I think the correct answer is just to DON'T use an object at all in that scenario specifically.

Upvotes: 2

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