class Flyer {    constructor(fname, speed) {      this.fname = fname;      this.speed = speed;    }    fly(){      console.log(this.fname,this.speed)    };  }  class Plane extends Flyer{    constructor(fname,speed,score) {      super(fname,speed);      this.score=score;    }    getScore(){      console.log(this.fname,this.speed,this.score);    };  }  var F16=new Plane('f16','100','50');  F16.fly();  F16.getScore();