Public, Private & Protected properties

Access modifiers help you enforce encapsulation — a key concept in object-oriented programming.

They allow you to control where and how class properties and methods are used.

✅ public (Default)

🔓 Accessible everywhere — inside the class, outside the class, and in subclasses.

class Car {
  public brand: string;

  constructor(brand: string) {
    this.brand = brand;
  }

  showBrand() {
    console.log(this.brand);
  }
}

const car = new Car("Toyota");
console.log(car.brand); // ✅ OK

✅ public is default if you don't explicitly write anything.

🔒 private

🔐 Accessible only inside the class where it is defined.

❌ Cannot be accessed from outside or from subclasses.

class BankAccount {
  private balance: number;

  constructor(balance: number) {
    this.balance = balance;
  }

  getBalance() {
    return this.balance;
  }
}

const acc = new BankAccount(1000);
// console.log(acc.balance);       // ❌ Error: Property 'balance' is private
console.log(acc.getBalance());     // ✅ OK

✅ Use private for sensitive or internal logic, like passwords or internal calculations.

🟡 protected

🟡 Accessible inside the class AND in derived (child) classes,

❌ but NOT accessible from outside the class.

class Employee {
  protected id: number;

  constructor(id: number) {
    this.id = id;
  }
}

class Manager extends Employee {
  getId() {
    return this.id;                       // ✅ OK
  }
}

const emp = new Manager(101);
// console.log(emp.id);                  // ❌ Error: Property 'id' is protected

✅ Use protected for things that subclasses need but the outside world doesn't.

🧪 Quick Comparison Table

🧠 Tip: Use with Constructor Shortcut

class Student {
  constructor(
    public name: string,
    private id: number,
    protected batch: string
  ) {}

  getId() {
    return this.id;
  }
}

✅ This short syntax automatically creates and initializes properties with access modifiers.

✅ Summary

• Use public for open API-like properties/methods

• Use private to protect internal data

• Use protected to share data only with child classes