protected

Learn subclass access with protected.

What is protected?

protected indicates that a member is accessible inside the class itself and its subclasses (those that extends it). Like private, it is closed to the outside, but open to subclasses.

class Animal {
  protected name: string;
  constructor(name: string) {
    this.name = name;
  }
}
class Dog extends Animal {
  bark(): string {
    return this.name + " havlıyor";
  }
}
const d = new Dog("Rex");
console.log(d.bark());

private vs protected

private is accessible only in the class where it is defined; not even in subclasses. protected is accessible both in the defining class and in subclasses. From outside, both are closed.

class Base {
  private secret: number = 1;
  protected shared: number = 2;
}
class Child extends Base {
  access(): number {
    // this.secret;  // error
    return this.shared;
  }
}

Exercise Write Animal and Dog classes

Define an Animal class with a protected name: string field and a constructor. Make Dog extends Animal and add a bark(): string method that returns this.name + " havlıyor". Create a new Dog("Rex") and call bark().

Show example solution

class Animal {
  protected name: string;
  constructor(name: string) {
    this.name = name;
  }
}

class Dog extends Animal {
  bark(): string {
    return this.name + " havlıyor";
  }
}

const d = new Dog("Rex");
console.log(d.bark());

Test yourself

Can a protected field be accessed from a subclass?
- Only from a static method
- No, not from anywhere
- Only from the same file
- Yes, accessible from a subclass
Show answer

Yes, accessible from a subclass — protected is accessible from the class itself and its subclasses (those that extend it). private is accessible only from the class itself; not from subclasses.

Complete the protected modifier

class Animal {
  ____ name: string;
}

Show answer

class Animal {
  protected name: string;
}

protected parts

protected

Accessible from class and subclass
extends Animal

Subclass definition
class Dog

Subclass
private

Not accessible in subclass

Next lesson: Parameter properties

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