class MathUtils {
  static add(a, b) {
    return a + b;
  }

  static multiply(a, b) {
    return a * b;
  }
}

// Called on the class, not an instance
console.log(MathUtils.add(2, 3));      // 5
console.log(MathUtils.multiply(4, 5)); // 20

// ❌ Cannot call on instances
const utils = new MathUtils();
console.log(utils.add(2, 3)); // TypeError: utils.add is not a function

class Config {
  static VERSION = '1.0.0';
  static MAX_RETRIES = 3;
  static DEFAULT_TIMEOUT = 5000;
}

console.log(Config.VERSION);        // '1.0.0'
console.log(Config.MAX_RETRIES);    // 3
console.log(Config.DEFAULT_TIMEOUT); // 5000

flowchart TB
    subgraph "Class (Config)"
        A["Static Members\nVERSION, MAX_RETRIES\ncreateDefault()"]
    end

    subgraph "Instances"
        B["instance1\nname: 'Alice'"]
        C["instance2\nname: 'Bob'"]
    end

    A -.->|"Config.VERSION"| D["Shared across all instances"]
    B -.->|"instance1.name"| E["Unique per instance"]
    C -.->|"instance2.name"| E

class Calculator {
  static PI = 3.14159;

  static circleArea(radius) {
    return this.PI * radius * radius; // this = Calculator
  }

  static create() {
    return new this(); // creates new Calculator instance
  }
}

console.log(Calculator.circleArea(5)); // 78.53975
const calc = Calculator.create(); // new Calculator()

class Parent {
  static greet() {
    return 'Hello from Parent';
  }
  static ID = 'parent';
}

class Child extends Parent {}

console.log(Child.greet()); // 'Hello from Parent'
console.log(Child.ID);      // 'parent'

// 1. Factory methods
class User {
  constructor(name) { this.name = name; }

  static createAnonymous() {
    return new User('Anonymous');
  }

  static createAdmin() {
    return new User('Admin');
  }
}

const anon = User.createAnonymous();
const admin = User.createAdmin();

// 2. Utility/helper methods
class Validator {
  static isEmail(str) {
    return /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(str);
  }

  static isUrl(str) {
    try { new URL(str); return true; }
    catch { return false; }
  }
}

console.log(Validator.isEmail('test@email.com')); // true
console.log(Validator.isUrl('https://example.com')); // true