Javascript Object Deep copy

Javascript Object deep copying means that the value of the new variable is disconnected from the original variable.
You can create the deep copying through JSON.parse method with JSON.stringify

Syntax:-


let new_object_name = JSON.parse(JSON.stringify(object_name));

Example:- Suppose you have employee object and copy object through JSON.parse() method with JSON.stringify into new_employee object then you change the firstName, city and state in new_employee object then it will not connected to old employee object.


let employee = {
    firstName: 'John',
    lastName: 'Taylor',
    address: {
        city: 'Mumbai',
        state: 'Maharashtra',
        country: 'India'
    }
};


let new_employee = JSON.parse(JSON.stringify(employee));
new_employee.firstName = 'Rom'; // disconnected
new_employee.address.city = 'New Delhi'; // disconnected
new_employee.address.state = 'Delhi'; // disconnected
console.log(new_employee);
console.log(employee);
Output:-
newEmployee:- {
firstName: “Rom”
lastName: “Taylor”
address: {city: “New Delhi”, state: “Delhi”, country: “India”}
}

oldEmployee:- {
firstName: “John”
lastName: “Taylor”
address: {city: “Mumbai”, state: “Maharashtra”, country: “India”}

}

Javascript Object Deep copy – Interview Questions

Q 1: What is a deep copy?

Ans: A deep copy creates an independent copy of all nested objects.

Q 2: How to create a deep copy?

Ans: JSON.parse(JSON.stringify(obj)).

Q 3: What is the limitation of the JSON method?

Ans: It cannot copy functions or undefined values.

Q 4: Does deep copy share references?

Ans: No.

Q 5: When is deep copy required?

Ans: When nested data must be completely independent.

Javascript Object Deep copy – Objective Questions (MCQs)

Q1. Deep copy duplicates ______.





Q2. Which method creates a deep copy (with limitations)?





Q3. Which modern method creates a true deep copy?





Q4. Deep copy prevents ______ between original and copied objects.





Q5. JSON-based deep copy does NOT support ______.