Bits of .NET

📦 ES6 Classes = OOP in JavaScript

Prototypes are confusing. ES6 Classes make OOP simple. Constructor, inheritance, methods.

📝 Class Basics

// Class declaration
class User {
    constructor(name, email) {
        this.name = name;
        this.email = email;
        this.createdAt = new Date();
    }
    
    greet() {
        return `Hello, ${this.name}!`;
    }
    
    getEmail() {
        return this.email;
    }
}

// Usage
const user = new User('Alice', 'alice@example.com');
console.log(user.greet()); // Hello, Alice!

// Class expression
const Person = class {
    constructor(name) {
        this.name = name;
    }
};

// Static methods
class MathUtils {
    static add(a, b) {
        return a + b;
    }
}
MathUtils.add(5, 3); // 8

// Getters and setters
class Product {
    constructor(name, price) {
        this._name = name;
        this._price = price;
    }
    
    get price() {
        return this._price;
    }
    
    set price(value) {
        if (value < 0) throw new Error('Price cannot be negative');
        this._price = value;
    }
}

🎯 Inheritance

// Inheritance
class Admin extends User {
    constructor(name, email, role) {
        super(name, email);
        this.role = role;
    }
    
    greet() {
        return `Hello, Admin ${this.name}!`;
    }
    
    manageUsers() {
        return 'Managing users...';
    }
}

const admin = new Admin('Bob', 'bob@example.com', 'admin');
console.log(admin.greet()); // Hello, Admin Bob!
console.log(admin.manageUsers()); // Managing users...

// Abstract class pattern
class Shape {
    constructor() {
        if (this.constructor === Shape) {
            throw new Error('Cannot instantiate abstract class');
        }
    }
    
    getArea() {
        throw new Error('Method must be implemented');
    }
}

class Circle extends Shape {
    constructor(radius) {
        super();
        this.radius = radius;
    }
    
    getArea() {
        return Math.PI * this.radius ** 2;
    }
}

// Mixins
const loggerMixin = {
    log(message) {
        console.log(`[LOG] ${message}`);
    }
};

class Service {
    // Use Object.assign
}
Object.assign(Service.prototype, loggerMixin);

💡 Class Tips

• Use constructor for initialization
• Use super() in derived classes
• Use static methods for utilities
• Use getters/setters for control
• Use inheritance for specialization