What methods can be used to clone an object in…

Spread operator ... (Shallow Copy).
Object.assign() (Shallow Copy).
JSON.parse(JSON.stringify(obj)) (Deep Copy, but with limitations).
Recursive function (Deep Copy).
Libraries (e.g., Lodash with method _.cloneDeep(), Deep Copy).

Comparison of Shallow vs. Deep Copy:

Copy Type	Description	Example
Shallow Copy	Copies surface properties. Nested objects remain by reference.	`const newObj = { ...origObj };` / `const newObj = Object.assign({}, origObj);`
Deep Copy	Copies all properties, including nested objects and arrays.	`const newObj = JSON.parse(JSON.stringify(origObj));` / Deep copy function / `_.cloneDeep(origObj)`

Limitations of JSON.parse(JSON.stringify(obj)):

Does not copy functions.
Does not copy undefined.
Does not copy Symbol.
Does not handle cyclic references.
Converts Date objects to strings.
Converts NaN, Infinity, and -Infinity to null.

Example of shallow copy with spread operator:

const originalObj = {
  name: 'Alice',
  address: {
    city: 'New York',
    zip: '10001'
  }
};

const shallowCopy = { ...originalObj };

shallowCopy.name = 'Bob'; // Only the copy changes
shallowCopy.address.city = 'Los Angeles'; // Both original and copy change (nested object by reference)

// console.log(originalObj.name); // Alice
// console.log(originalObj.address.city); // Los Angeles

Example of deep copy with JSON.parse(JSON.stringify()):

const originalObj = {
  name: 'Alice',
  address: {
    city: 'New York'
  },
  greet: function() {
    console.log('Hello');
  },
  undefinedProp: undefined
};

const deepCopy = JSON.parse(JSON.stringify(originalObj));

deepCopy.name = 'Bob';
deepCopy.address.city = 'Los Angeles';

// console.log(originalObj.name); // Alice
// console.log(originalObj.address.city); // New York
// console.log(deepCopy.greet); // undefined (function not copied)
// console.log(deepCopy.undefinedProp); // undefined (undefined not copied)

Example of recursive function for deep copying:

function deepClone(obj) {
  if (obj === null || typeof obj !== 'object') {
    return obj; // Base case: primitives or null
  }

  // Handle Array
  if (obj instanceof Array) {
    const copy = [];
    for (let i = 0; i < obj.length; i++) {
      copy[i] = deepClone(obj[i]);
    }
    return copy;
  }

  // Handle Object
  if (obj instanceof Object) {
    const copy = {};
    for (const key in obj) {
      if (obj.hasOwnProperty(key)) {
        copy[key] = deepClone(obj[key]);
      }
    }
    return copy;
  }

  // For other object types not needed in cloning scenario
  throw new Error("Unable to copy obj! Its type isn't supported.");
}

const originalObj = {
  name: 'Alice',
  address: {
    city: 'New York'
  },
  numbers: [1, 2, { three: 3 }]
};

const deepCopy = deepClone(originalObj);

deepCopy.name = 'Bob';
deepCopy.address.city = 'Los Angeles';
deepCopy.numbers[2].three = 4;

// console.log(originalObj.name); // Alice
// console.log(originalObj.address.city); // New York
// console.log(originalObj.numbers[2].three); // 3

What methods can be used to clone an object in JavaScript?