Why is this array being passed by reference and not by value, and how can I change this?

Question

I was working on a bug in some code that I wrote, and the culprit turned out to be this snippet (simplified for the sake of the question):

var a = [1, 2, 3, 5, 4];
// later...
function f(arr) {
    var sorted = arr.sort();
    // other stuff
}
// later...
console.log(a);
// logs [1, 2, 3, 4, 5]!

My question is, why does a stay sorted after the function is done? Surely in JS all variables are passed by value as opposed to reference?

I believe this answers your question http://stackoverflow.com/questions/2835070/is-there-thing-like-pass-by-value-pass-by-reference-in-javascript#2835203 — Dai, Nov 19 '14 at 09:09

score 0 · Answer 1 · edited May 23 '17 at 12:27

0

Look at this for a full description

Is JavaScript a pass-by-reference or pass-by-value language?

edited May 23 '17 at 12:27

Community

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answered Nov 19 '14 at 09:16

Luca Rasconi

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Sorry, but this should be a comment, not an answer. – georg Nov 19 '14 at 09:33
You are right but I can't add comments. – Luca Rasconi Nov 19 '14 at 10:22

score -1 · Answer 2 · answered Nov 19 '14 at 09:19

-1

Array is an Object. In javascript all Objects are passed by reference.

answered Nov 19 '14 at 09:19

murli2308

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Sorry, but this answer is wrong. Javascript doesn't have "pass by reference" (like in C++ or PHP). – georg Nov 19 '14 at 09:34
Objects are passed by reference only in javascript and I am sure about it. I made a simple fiddle for it. http://jsfiddle.net/murli2308/npag0fj4/ – murli2308 Nov 19 '14 at 09:49
This topic has been discussed ad nauseum, please read the answers in the linked thread. In short, js passes everything by value, but this very value is always a reference (=pointer). – georg Nov 19 '14 at 10:01

Why is this array being passed by reference and not by value, and how can I change this?

2 Answers2