Q136- Write a function to deep clone an object. What is the difference between shallow copy and deep copy?

Cloning an object means creating a copy of the object. There are two types:

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1️⃣ Shallow Copy

• Copies only the first level of the object.
• Nested objects or arrays are shared between original and copy.
• Changes in nested objects affect both.

Example of Shallow Copy:

const original = { name: "Alice", address: { city: "Paris" } };
const shallowCopy = { ...original };

shallowCopy.address.city = "London";

console.log(original.address.city); // London → changed!

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2️⃣ Deep Copy

• Copies all levels of the object.
• Nested objects are completely independent.
• Changes in the copy do not affect the original.

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Deep Clone Function (Recursive)

function deepClone(obj) {
  if (obj === null || typeof obj !== "object") {
    return obj; // return primitive values as is
  }

  if (Array.isArray(obj)) {
    return obj.map(item => deepClone(item)); // clone each array element
  }

  const clonedObj = {};
  for (let key in obj) {
    if (obj.hasOwnProperty(key)) {
      clonedObj[key] = deepClone(obj[key]); // recursive clone
    }
  }
  return clonedObj;
}

// Example
const original = {
  name: "Alice",
  address: { city: "Paris", zip: 75000 },
  hobbies: ["reading", "traveling"]
};

const cloned = deepClone(original);
cloned.address.city = "London";
cloned.hobbies.push("coding");

console.log(original.address.city); // Paris
console.log(original.hobbies);      // ["reading", "traveling"]

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⚖️ Key Differences Table

Feature	Shallow Copy	Deep Copy
Levels Copied	Only first level	All nested levels
Nested Objects	Shared	Independent
Example Methods	{ ...obj }, Object.assign()	Custom recursive function, structuredClone() in modern JS

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✅ In Short:

• Shallow copy → quick, but nested objects are linked.
• Deep copy → full independent clone, safe for complex objects.

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Note: Modern JS also has structuredClone(obj) which performs deep cloning.