// Object literal (most common)
const person = {
  name: 'Ali',
  age: 25,
  greet() {
    console.log(`Hello, I'm ${this.name}`);
  }
};

// Properties can be added dynamically
person.country = 'UAE';
delete person.age;

function createPerson(name, age) {
  return {
    name,
    age,
    greet() {
      console.log(`Hi, I'm ${this.name}`);
    }
  };
}

const ali = createPerson('Ali', 25);

function Person(name, age) {
  // Instance properties
  this.name = name;
  this.age = age;
  
  // Method (created for each instance)
  this.greet = function() {
    console.log(`Hello, I'm ${this.name}`);
  };
}

const ali = new Person('Ali', 25);

// Adding to prototype (shared across instances)
Person.prototype.introduce = function() {
  console.log(`My name is ${this.name}, age ${this.age}`);
};

// Prototype chain lookup
ali.introduce(); // Checks ali → Person.prototype → Object.prototype → null

function Student(name, age, grade) {
  Person.call(this, name, age); // "Super" constructor
  this.grade = grade;
}

// Set up prototype chain
Student.prototype = Object.create(Person.prototype);
Student.prototype.constructor = Student;

// Add methods
Student.prototype.study = function() {
  console.log(`${this.name} is studying hard!`);
};

const personProto = {
  greet() {
    console.log(`Hello from ${this.name}`);
  }
};

const ali = Object.create(personProto);
ali.name = 'Ali';

class Person {
  // Constructor (called with 'new')
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
  
  // Instance method
  greet() {
    console.log(`Hello, I'm ${this.name}`);
  }
  
  // Static method
  static compareAges(a, b) {
    return a.age - b.age;
  }
}

class Student extends Person {
  constructor(name, age, grade) {
    super(name, age); // Must call super first
    this.grade = grade;
  }
  
  study() {
    console.log(`${this.name} is studying`);
  }
  
  // Override method
  greet() {
    super.greet(); // Call parent method
    console.log(`I'm in grade ${this.grade}`);
  }
}

class ModernClass {
  // Public field (instance property)
  publicField = 1;
  
  // Private field (starts with #)
  #privateField = 2;
  
  // Static public field
  static staticField = 3;
  
  // Static private field
  static #staticPrivateField = 4;
  
  // Private method
  #privateMethod() {
    return this.#privateField;
  }
}

const obj = {};

Object.defineProperty(obj, 'readOnlyProp', {
  value: 42,
  writable: false,       // Can't be changed
  enumerable: true,      // Shows up in for...in
  configurable: false    // Can't be deleted/reconfigured
});

class Temperature {
  constructor(celsius) {
    this.celsius = celsius;
  }
  
  get fahrenheit() {
    return this.celsius * 1.8 + 32;
  }
  
  set fahrenheit(value) {
    this.celsius = (value - 32) / 1.8;
  }
}

const temp = new Temperature(25);
console.log(temp.fahrenheit); // 77
temp.fahrenheit = 100;

class AppConfig {
  constructor() {
    if (AppConfig.instance) {
      return AppConfig.instance;
    }
    
    this.settings = { theme: 'dark' };
    AppConfig.instance = this;
  }
}

const config1 = new AppConfig();
const config2 = new AppConfig();
console.log(config1 === config2); // true

class UserFactory {
  static createUser(type) {
    switch(type) {
      case 'admin':
        return new Admin();
      case 'customer':
        return new Customer();
      default:
        throw new Error('Invalid user type');
    }
  }
}

class EventEmitter {
  constructor() {
    this.events = {};
  }
  
  on(event, listener) {
    (this.events[event] || (this.events[event] = [])).push(listener);
  }
  
  emit(event, ...args) {
    this.events[event]?.forEach(listener => listener(...args));
  }
}

const emitter = new EventEmitter();
emitter.on('login', user => console.log(`${user} logged in`));
emitter.emit('login', 'Ali');

const CounterModule = (() => {
  let count = 0;
  
  return {
    increment() {
      count++;
    },
    getCount() {
      return count;
    }
  };
})();

class Character {
  constructor(name, level) {
    this.name = name;
    this.level = level;
    this.health = 100;
  }
  
  attack(target) {
    const damage = this.level * 2;
    target.takeDamage(damage);
    console.log(`${this.name} attacks ${target.name} for ${damage} damage`);
  }
  
  takeDamage(amount) {
    this.health -= amount;
    if (this.health <= 0) {
      console.log(`${this.name} has been defeated!`);
    }
  }
}

class Mage extends Character {
  constructor(name, level, mana) {
    super(name, level);
    this.mana = mana;
  }
  
  castSpell(target) {
    if (this.mana >= 10) {
      const damage = this.level * 3;
      this.mana -= 10;
      target.takeDamage(damage);
      console.log(`${this.name} casts a spell on ${target.name}!`);
    } else {
      console.log("Not enough mana!");
    }
  }
}

// Usage
const warrior = new Character('Conan', 5);
const wizard = new Mage('Gandalf', 7, 50);

warrior.attack(wizard);
wizard.castSpell(warrior);

// Faster (direct property access)
obj.propertyName;

// Slower (dynamic property access)
obj['property' + 'Name'];