Issues with global variable in JavaScript

Question

My issues with global variable in JavaScript

Hello everyone, I am facing an issues with global variable in JavaScript. My issues as given below.

Why the global variable "g_MobileAssociatedPlans" is getting updated whenever I modifying the other input variable "data".

var g_MobileAssociatedPlans = "";

$(function () {
    var data = { "Item1": "Burger", "Item2": "Soft Drink" };

    displayMobileDevices(data);
});

function displayMobileDevices(data) {

    g_MobileAssociatedPlans = data;

    alert(JSON.stringify(g_MobileAssociatedPlans));

    data.Item1 = "Wine";

    alert(JSON.stringify(g_MobileAssociatedPlans));
}

Please see the above example and review it and revert me the issues. Thank you!

Within your displayMobileDevices function, you assign the reference of data to the g_MobileAssociatedPlans so whenever data changes, so will g_MobileAssociatedPlans. — Anthony Forloney
– Anthony Forloney, Commented Jun 10, 2015 at 11:36
what is your problem ? i can't find any problems here..what is the issue? and also data is not a varibale it is an object.and the objects are passed by reference — Arunprasanth K V
– Arunprasanth K V, Commented Jun 10, 2015 at 11:37

Arunprasanth K V · Accepted Answer · 2015-06-10 11:46:29Z

2

Because you are assigning object not value,it will be assigning object reference, for getting the desired output you have to clone the object

g_MobileAssociatedPlans = JSON.parse(JSON.stringify(data));

Or

g_MobileAssociatedPlans = jQuery.extend({}, data);

Fiddle

edited Jun 10, 2015 at 11:46

Arunprasanth K V

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answered Jun 10, 2015 at 11:37

Balachandran

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Comments

Community · Accepted Answer · 2017-05-23 10:28:08Z

1

You are passing the reference. Not value. Only primitive types (like numbers, boolean) can be passed by reference. And, Objects are passed by value. If you don't want reference, clone the object.
The easiest way to clone JSON object is JSON.parse(JSON.stringify(originalObject)).
refer to What is the most efficient way to deep clone an object in JavaScript?

edited May 23, 2017 at 10:28

CommunityBot

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answered Jun 10, 2015 at 11:46

Navaneeth

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Comments

Anil Singh · Accepted Answer · 2015-06-10 11:58:29Z

1

Please update your code like below

var g_MobileAssociatedPlans = "";
$(function () {
    var data = { "Item1": "Burger", "Item2": "Soft Drink" };
    displayMobileDevices(data);
});

function displayMobileDevices(data) {
    g_MobileAssociatedPlans = JSON.parse(JSON.stringify(data));
    alert(JSON.stringify(g_MobileAssociatedPlans));
    data.Item1 = "Wine";
    alert(JSON.stringify(g_MobileAssociatedPlans));
}

answered Jun 10, 2015 at 11:58

Anil Singh

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Comments

Community · Accepted Answer · 2017-05-23 12:16:02Z

0

That's because objects in JavaScript are passed by reference. More about that. Try Most elegant way to clone a JavaScript object.

edited May 23, 2017 at 12:16

CommunityBot

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answered Jun 10, 2015 at 11:36

andale

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