will Array.sort() preserve the order of the array, where possible?

Question

I suppose it depends on how it's implemented. I'd love it if someone would come back and tell me "yes, in virtually all browsers, order of items will be changed only when necessary to satisfy the conditions of the sort.

weiyin · Accepted Answer · 2009-02-02 21:23:11Z

7

What you're looking for is whether or not the algorithm is "stable". It is known that Firefox's is not, while IE's is. The javascript standard doesn't require a stable sorting algorithm.

Edit: Firefox 3+ has a stable sort. Please see http://www.hedgerwow.com/360/dhtml/js_array_stable_sort.html

answered Feb 2, 2009 at 21:23

weiyin

6,9794 gold badges51 silver badges60 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

IAdapter · Accepted Answer · 2009-02-02 21:19:37Z

1

Every browsers has different implemantation, so dont count on it.

answered Feb 2, 2009 at 21:19

IAdapter

65.6k73 gold badges188 silver badges243 bronze badges

Comments

toddk · Accepted Answer · 2009-02-02 21:27:00Z

0

I believe it depends on the type of objects you are sorting within your array. You can supply a "sort function" to array.sort() to determine the rules for sorting a particular object. For example, consider the function:

function sortInt(a, b){
   if ( a < b )
    return -1;
   else if ( a == b )
     return 0;
   else if ( a > b )
     return 1;
}

So this is obviously contrived but you can apply this same type of idea to any object that is "comparable". You will always return a -1, 0, or 1 depending if the a is less than, equal to, or greater than b (respectfully).

You would then say: array.sort(sortInt);

Caveat:

Forgive me if the syntax isn't perfect as I do not have an example on hand. I also am not sure about the stability of Array.sort() from a cross browser perspective.

Edit: Fixed the formatting for the psuedo code snippet

answered Feb 2, 2009 at 21:27

toddk

8811 gold badge12 silver badges20 bronze badges

2 Comments

some Over a year ago

function sortInt(a,b) { return (a>b) - (a<b); }

Jochem Van Der Spek Over a year ago

this does NOT 'preserve' the order of the array where evaluations result in 0. ie array [ a, b, c, d ] does NOT result in identically ordered array when all evaluations result in 0 (on Chrome 26 at least)

olliej · Accepted Answer · 2009-02-02 23:54:31Z

0

All the major browsers have stable sorting algorithms, and also (because there is some stupid code out there) they can handle inconsistent compare functions.

answered Feb 2, 2009 at 23:54

olliej

36.9k9 gold badges61 silver badges55 bronze badges

Collectives™ on Stack Overflow

will Array.sort() preserve the order of the array, where possible?

4 Answers 4

Comments

Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related