Inheritance & Prototypes — Series 3

Preview — 3 of 10 questions

What is logged?

javascript

class A {
  hello() {
    return 'A';
  }
}
class B {
  hello() {
    return 'B';
  }
}

const obj = new A();
Object.setPrototypeOf(obj, B.prototype);

console.log(obj.hello(), obj instanceof A, obj instanceof B);

AA true false

BB false true

CB true true

DTypeError: Cannot set prototype of an instance

What is logged?

javascript

class Widget {
  render() {
    return 'base';
  }
}

const w = new Widget();
w.render = () => 'own';
console.log(w.render());

delete w.render;
console.log(w.render());

Aown, undefined

Bbase, base

Cown, TypeError: w.render is not a function

Down, base

What is logged?

javascript

class Base {
  static describe() {
    return 'Base';
  }
  get info() {
    return 'base';
  }
}

class Child extends Base {
  static describe() {
    return super.describe() + ' -> Child';
  }
  get info() {
    return `${super.info}+child`;
  }
}

console.log(Child.describe(), new Child().info);

ABase -> Child base+child

BBase -> Child undefined+child

CChild -> Child base+child

DTypeError: super is only allowed in a constructor

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