extends

class Square extends Polygon {
  constructor(length) {
    //     ,
    //     length  
    // ,   width  height,
    //  Polygon
    super(length, length);
    // :
    //   ,  super()   
    //   this.   , 
    //  .
    this.name = "Square";
  }

  get area() {
    return this.height * this.width;
  }
}

class myDate extends Date {
  constructor() {
    super();
  }

  getFormattedDate() {
    var months = [
      "Jan",
      "Feb",
      "Mar",
      "Apr",
      "May",
      "Jun",
      "Jul",
      "Aug",
      "Sep",
      "Oct",
      "Nov",
      "Dec",
    ];
    return (
      this.getDate() + "-" + months[this.getMonth()] + "-" + this.getFullYear()
    );
  }
}

class nullExtends extends null {
  constructor() {}
}

Object.getPrototypeOf(nullExtends); // Function.prototype
Object.getPrototypeOf(nullExtends.prototype); // null

new nullExtends(); //ReferenceError: this is not defined