How javascript sorts arrays with the same property?

Question

If the two elements have the same property value on which we sort the array then how javascript order them i mean if you have this array for example :

let array = [{id:0,name:"sam",age:"20"},
             {id:0,name:"john",age:"21"},
             {id:1,name:"fred",age:"30"}]

let's suppose that i want to sort this array by id ascending then how can i know which one will appear first :

{id:0,name:"sam",age:"20"}

OR

{id:0,name:"john",age:"21"}

depends on how your sorting method is defined. Are you using `.sort()`? — Nick Parsons, Jul 04 '19 at 16:26
It depends on the vendors (browser,engine) sorting behavior implementation. — Patrick Evans, Jul 04 '19 at 16:29
https://stackoverflow.com/questions/31213696/sort-array-items-and-preserve-order-of-same-elements — Mihályi Zoltán, Jul 04 '19 at 16:29
the newer implementations of `sort` keeps the order for comparisons which return zero. — Nina Scholz, Jul 04 '19 at 16:31

Sagiv b.g · Answer 1 · 2019-07-04T16:35:26.557

2

Up until now the Array.prototype.sort was not a stable sort because there was no mentioning for it in the spec so actually there was no guaranty for a stable (consistent) order.

Though recently, the spec has changed and the V8 engine implemented it as a stable sort.

edited Jul 04 '19 at 16:35

answered Jul 04 '19 at 16:31

Sagiv b.g

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It is now. ..... – T.J. Crowder Jul 04 '19 at 16:32
That's why i wrote _"Though recently, the V8 engine implemented it as a stable sort."_ – Sagiv b.g Jul 04 '19 at 16:32
It's not just V8. The language specification changed as of ES2019 to **require** a stable sort of implementations. Your first paragraph says it isn't specified. It is. – T.J. Crowder Jul 04 '19 at 16:33
Thanks @T.J.Crowder! fixed my answer – Sagiv b.g Jul 04 '19 at 16:35

T.J. Crowder · Answer 2 · 2019-07-04T16:44:21.500

1

I realized after answering that this is a duplicate. See my answer to the dupetarget. Briefly: As of ES2019, Array#sort is stable, so in your example "sam" will remain before "john". Prior to ES2019, that wasn't necessarily true, they could have had their order reversed.

edited Jul 04 '19 at 16:44

answered Jul 04 '19 at 16:31

T.J. Crowder

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How javascript sorts arrays with the same property?

2 Answers2