JavaScript How to delete key from copied object? [duplicate]

Question

I have query object

var q = {
    age: 10, 
    'profile.contry': 'india'
};

Now I duplicate the q variable and remove key from a duplicate variable.

var duplicateQ = q;
delete duplicateQ['profile.contry']; // I have removed 'profile.country' from duplicateQ.

console.log(q); //Object { age: 10 }
console.log(duplicateQ); //Object { age: 10 }

Why are both the variables affected? How can I remove the property from only one of them?

Answer 1

It's because q and duplicateQ refer to the same object. Thus, when you delete a property on one object, it effects both (since they both point to the same object).

You need to copy/clone the object.

In ES6, you can use the .assign() method:

var q = {age:10, 'profile.contry': 'india'};
var duplicateQ = Object.assign({}, q);
delete duplicateQ['profile.contry'];

Output:

console.log(q);
// {age: 10, profile.contry: "india"}

console.log(duplicateQ);
// Object {age: 10}