Javascript: reference an array with a variable, instead of duplicating it

Question

let's say I have two javascript arrays, like this:

arrA = [1,2,3]
arrB = [4,5,6]

Is there a way I can reference them with different variable names down then road? If I do this:

arrC = arrA
arrD = arrB

it makes copies of the initial arrays, instead of making a pointer/reference to them. So, if I mess with the value of arrC, arrA isn't updated. Is there a way to get around this?

Thanks.

You'll need to provide a sample of code showing your scenario, since arrC = arrA does just make a new reference to the same array. — Joe Enos
– Joe Enos, Commented Apr 17, 2013 at 13:32
I used below code in firebug: 'arrA = [1, 2, 3]; arrC = arrA; arrC[2] = 9; console.log(arrA)'. It shows that arrA is updated. — Niraj Nawanit
– Niraj Nawanit, Commented Apr 17, 2013 at 13:35
Yeah, it looks like I was re-assigning my variable name elsewhere in my code. Thanks for the help - I'll accept an answer as soon as it lets me. — Kevin Whitaker
– Kevin Whitaker, Commented Apr 17, 2013 at 13:42

Denys Séguret · Accepted Answer · 2013-04-17 13:31:22Z

5

No, it doesn't make a copy. If you change arrC, it will change arrA too.

Try this :

var arrA = [1,2,3];
var arrC = arrA;
arrC.push(26);
console.log(arrA);

You'll see [1, 2, 3, 26] in the console.

The contrary is true : if you want to make a copy, you have to do it explicitly, for example with

var arrC = arrA.slice();

answered Apr 17, 2013 at 13:31

Denys Séguret

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3 Comments

jbabey Over a year ago

and if you did want to make a copy, use var copy = arr.splice();

jbabey Over a year ago

what do you mean? it's the same thing you just edited your answer to include :)

Denys Séguret Over a year ago

I had edited before, but I was mostly referring to the fact that splice (with a p) doesn't return a copy.

Community · Accepted Answer · 2017-05-23 11:43:18Z

0

Follow this post and Create an array within an object, this is a simple way.

javascript variable reference/alias

edited May 23, 2017 at 11:43

CommunityBot

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answered Apr 17, 2013 at 13:35

laxy

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1 Comment

Denys Séguret Over a year ago

1) Don't just link to another question, do it in comment so that somebody can mark it as duplicate. 2) I don't see how it's related. 3) try to gain some rep so that you can comment instead of writing answers that aren't answers. 4) welcome on SO :)

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