Objects in JavaScript

// Object literal (most common)
const user = {
  name: "Shiva",
  age: 25,
  isAdmin: true,
  address: { city: "Mumbai", country: "India" }
};

// Shorthand properties (ES6)
const name = "Shiva";
const age = 25;
const user = { name, age }; // same as { name: name, age: age }

// Computed property names
const key = "role";
const obj = { [key]: "admin" }; // { role: "admin" }

// Dot notation
user.name; // "Shiva"

// Bracket notation (required for dynamic keys)
const key = "name";
user[key]; // "Shiva"

// Optional chaining
user.address?.city; // "Mumbai"
user.phone?.number; // undefined (no error)

const calc = {
  value: 0,
  add(n) {
    this.value += n;
    return this; // enables chaining
  },
  result() {
    return this.value;
  }
};

calc.add(10).add(5).result(); // 15

const user = { name: "Shiva", age: 25, role: "admin" };

Object.keys(user);    // ["name", "age", "role"]
Object.values(user);  // ["Shiva", 25, "admin"]
Object.entries(user); // [["name", "Shiva"], ["age", 25], ["role", "admin"]]

// Iterate over object
for (const [key, value] of Object.entries(user)) {
  console.log(`${key}: ${value}`);
}

// Merge objects
const config = Object.assign({}, defaults, userPrefs);
const config = { ...defaults, ...userPrefs }; // modern spread

// freeze — no changes at all
const frozen = Object.freeze({ name: "Shiva" });
frozen.name = "Alex"; // silently fails
frozen.age = 25;      // silently fails

// seal — can modify existing, can't add/delete
const sealed = Object.seal({ name: "Shiva" });
sealed.name = "Alex"; // ✅ Works
sealed.age = 25;      // ❌ Fails

// Both are SHALLOW — nested objects are NOT affected

const user = {
  firstName: "Shiva",
  lastName: "Yadav",

  get fullName() {
    return `${this.firstName} ${this.lastName}`;
  },

  set fullName(name) {
    [this.firstName, this.lastName] = name.split(" ");
  }
};

user.fullName; // "Shiva Yadav"
user.fullName = "Alex Kumar";
user.firstName; // "Alex"

const original = { name: "Shiva", address: { city: "Mumbai" } };

const copy = { ...original };
copy.address.city = "Delhi";
console.log(original.address.city); // "Delhi" — shared reference!

// ✅ structuredClone (modern — use this!)
const deep = structuredClone(original);
deep.address.city = "Delhi";
console.log(original.address.city); // "Mumbai" — independent

// ❌ JSON trick (loses functions, dates, undefined)
const deep = JSON.parse(JSON.stringify(original));

Object.defineProperty(user, "id", {
  value: 1,
  writable: false,     // can't change
  enumerable: false,   // hidden from Object.keys, for...in
  configurable: false  // can't delete or reconfigure
});

function createServer(options = {}) {
  const config = {
    port: 3000,
    host: "localhost",
    debug: false,
    ...options
  };
  return config;
}

const isEmpty = (obj) => Object.keys(obj).length === 0;

const { password, ...safeUser } = user;
// safeUser has everything except password

{ a: 1 } === { a: 1 } // false — different references!

// Compare by value:
JSON.stringify(obj1) === JSON.stringify(obj2); // fragile but works