class a {

  f() {

    console.log('a')

  }

  get f2() {

    console.log('f2')

    return (this['f'] = this.f.bind(this));

  }

}

class b extends a {

  constructor() {

    super()

    this.f = this.f.bind(this)

  }

  f() {

    console.log('b')

    super.f2();

  }

  get f2() {

    return (this['f'] = this.f.bind(this));

  }

}

let instance = new b();

instance.f2();

// for (var i = 0; i < 5; ++i) {

//   console.log('invoking');

//   instance.f2();

//   console.log('---');

// }

class a {

  // constructor() {

  //   this.f2 = this.f.bind(this);

  // }

  f() {

    console.log('a')

  }

  f2() {

    // console.log(this)

    console.log('f2')

    if (!this.f3) {

      this.f3 = this.f.bind(this);

    }

    return this.f3

  }

}

class b extends a {

  // constructor() {

  //   super()

  //   this.f = this.f.bind(this)

  // }

  constructor() {

    super();

    this.f2 = this.f.bind(this);

  }

  f() {

    console.log('b')

    super.f2();

    this.f2 = this.f.bind(this);

  }

  // get f2() {

  //   console.log(this)

  //   return (this['f'] = this.f.bind(this));

  // }

}

let instance = new b();

instance.f2();

for (var i = 0; i < 5; ++i) {

  console.log('invoking');

  instance.f2();

  console.log('---');

}