Store result of array.sort in another variable

Question

This seems like a simple question but I can't find much info on this.

var array1 = new Array(4, 3, 1, 2, 0, 5);
var array2 = array1;
array2.sort(function(a, b) {
    return a - b;
})

Expected behavior: array2 is sorted and array1 is in the original order starting with 4.

Actual result: both arrays are sorted.

How can I sort array1 - while maintaining array1 and storing the results of the sort in array2? I thought that doing array2 = array1 would copy the variable, not reference it. However, in Firefox's console both arrays appear sorted.

Why is the default behavior to reference the original array instead of copying it? — tomysshadow
– tomysshadow, Commented Aug 9, 2016 at 7:34
stackoverflow.com/questions/7486085/…. Some methods are doing changes on reference, some create new array. Check array documentation. — Maciej Sikora
– Maciej Sikora, Commented Aug 9, 2016 at 7:35
Should have realized that the two arrays are one and the same not just with the sort function. I guess that basically makes this a duplicate question, it just wasn't obvious at first the two arrays are always the same not just with the sort function. — tomysshadow
– tomysshadow, Commented Aug 9, 2016 at 7:39

alejandromav · Accepted Answer · 2016-08-09 08:04:26Z

1

That's becasue with var array2 = array1; you're making a new reference to the object, so any manipulation to array2 will affect array1, since the're basically the same object.

JS doesn't provide a propner clone function/method, so try this widely adopted workarround:

var array1 = new Array(4, 3, 1, 2, 0, 5);
var array2 = JSON.parse(JSON.stringify(array1));
array2.sort(function(a, b) {
    return a - b;
});

Hope it helps :)

edited Aug 9, 2016 at 8:04

answered Aug 9, 2016 at 7:38

alejandromav

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2 Comments

nnnnnn Over a year ago

"you're making a shallow copy of the object," - Nope, you're not making a copy of the object at all, you're just making a second reference to the same object.

alejandromav Over a year ago

@nnnnnn that's more accurate

Community · Accepted Answer · 2017-05-23 11:44:18Z

0

You can copy a array with slice method

var array1 = new Array(4, 3, 1, 2, 0, 5);
var array2 = array1.slice();

edited May 23, 2017 at 11:44

CommunityBot

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answered Aug 9, 2016 at 7:43

Radian Jheng

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1 Comment

nnnnnn Over a year ago

Note that this makes a shallow copy, which should be fine for the OP's array of numbers but may or may not be enough with an array of objects.

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