Change object via function parameter

Question

Please, could you help me to figure out my problem. I'm trying to return changed object via function parameter but it does not work for me as I expect. I'm using Node.js version 13.8.0 under Windows 10 Professional Edition.

Below is a code snippet that I'm struggling with:

function a(x)
{
    var r = { v1: 0.0, v2: 0.0};
    r.v1 = 2.0 * x;
    r.v2 = x * x;
    return r;
}

function b(x, r)
{
    r = a(x);
}

var rr = { v1: 100.0, v2: 1000.0 };
b(5.0, rr);

console.log(rr);

At the end I expect that console.log(rr) will print out "{ v1: 10.0, v2: 25.0 }" but instead I have the "{ v1: 100.0, v2: 1000.0 }".

ESLint shows one error that does not seems to me important. 1 What I'm doing wrong?

Does this answer your question? [JavaScript by reference vs. by value](https://stackoverflow.com/questions/6605640/javascript-by-reference-vs-by-value) — theBittor, Apr 18 '20 at 12:07

Sifat Haque · Accepted Answer · 2020-04-18T12:30:41.780

0

Here is the solution for your issue.

function a(x)
{
    var r = { v1: 0.0, v2: 0.0};
    r.v1 = 2.0 * x;
    r.v2 = x * x;
    return r;
}

function b(x, r)
{
    let changedObj = a(x);
    r.v1 = changedObj.v1;
    r.v2 = changedObj.v2;
    
}

var rr = { v1: 100.0, v2: 1000.0 };
b(5.0, rr);

console.log(rr);

edited Apr 18 '20 at 12:30

answered Apr 18 '20 at 12:08

Sifat Haque

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That's not that I'm looking for. I understand that I can *return* updated object but I NEED TO RETURN IT VIA FUNCTION PARAMETER. (Just in case if there will be two, three or more objects to return.) – Lieh Tzu Apr 18 '20 at 12:14
@LiehTzu Would you please check now? – Sifat Haque Apr 18 '20 at 12:31

Change object via function parameter

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