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!

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

more