Access Modifiers

Example

class Account {
  public holder: string;
  protected balance: number;
  private pin: string;

  constructor(holder: string, balance: number, pin: string) {
    this.holder = holder;
    this.balance = balance;
    this.pin = pin;
  }

  checkPin(input: string): boolean {
    return input === this.pin;
  }
}

class SavingsAccount extends Account {
  addInterest(ratePercent: number): number {
    this.balance += (this.balance * ratePercent) / 100; // protected: OK in subclass
    return this.balance;
  }
}

const acc = new SavingsAccount("Neha", 10000, "4321");
console.log(acc.holder, acc.checkPin("1111"), acc.addInterest(4));

Output

Neha false 10400

Example

Reading private or protected members from outside is an error (TS2341 and TS2445).

class Account {
  protected balance = 100;
  private pin = "4321";
}

const acc = new Account();
console.log(acc.balance);
console.log(acc.pin);

Compiler output (tsc)

Line 7: error TS2445: Property 'balance' is protected and only accessible within class 'Account' and its subclasses.
Line 8: error TS2341: Property 'pin' is private and only accessible within class 'Account'.