Object Cloning - Shallow & Deep.

object-copy.js

// shallow cloning - object create method
const parent = {
  source: function () {
    return 'parent';
  },
  type: 'obj',
  hello: {
    world: 'Hello World',
    state: 'Hello Statesmen',
  },
};
const child = Object.create(parent);
child.type = 'new obj';
child.hello.state = 'Hello State';
console.log(parent);
console.log(child.source);

// shallow cloning - object assign method
const parent1 = {
  source: function () {
    return 'parent1';
  },
  type: 'obj',
  hello: {
    world: 'Hello World',
    state: 'Hello Statesmen',
  },
};
const child1 = Object.assign({}, parent1);
child1.type = 'new obj';
child1.hello.state = 'Hello State';
console.log(parent1);
console.log(child1.source);

// deep cloning - JSON way but not recomended as you can see function/Date etc returns undefined
const parent2 = {
  source: function () {
    return 'parent2';
  },
  type: 'obj',
  hello: {
    world: 'Hello World',
    state: 'Hello Statesmen',
  },
};
const child2 = JSON.parse(JSON.stringify(parent2));
child2.type = 'new obj';
child2.hello.state = 'Hello State';
console.log(parent2);
console.log(child2.source);

// deep cloning - custom recursive function
const parent3 = {
  source: function () {
    return 'parent3';
  },
  type: 'obj',
  hello: {
    world: 'Hello World',
    state: 'Hello Statesmen',
  },
};
const child3 = _deepClone(parent3);
child3.type = 'new obj';
child3.hello.state = 'Hello State';
console.log(parent3);
console.log(child3.source);

function _deepClone(obj) {
  if (typeof obj !== 'object' || obj === null) {
    return obj
  }
  let newObj = Array.isArray(obj) ? [] : {};
  for (const key in obj) {
    if (typeof obj[key] === 'object') {
      newObj[key] = _deepClone(obj[key]);
    } else {
      newObj[key] = obj[key];
    }
  }
  return newObj
}